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Thanks all and noted about the ziptie trick. Today might be a full abort until I've identified my full and actual fuel routing, the SM I'm using covers many VanVans, and either the 2018 model or the california evap system means there's no fuel shutoff where pictured, and gently caress if I can find one yet. I'll need to pick up a fuel can if I have to drain the whole tank.
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Jan 8, 2022 23:23
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Remy Marathe posted:Thanks all and noted about the ziptie trick. Today might be a full abort until I've identified my full and actual fuel routing, the SM I'm using covers many VanVans, and either the 2018 model or the california evap system means there's no fuel shutoff where pictured, and gently caress if I can find one yet. I'll need to pick up a fuel can if I have to drain the whole tank. Is this a carbureted bike? If so, and there is no manual tap, there will be a vacuum operated tap that automatically shuts off. I've never seen an EFI vanvan but I assume they exist. You're overthinking this. It is a brutally, desperately simple bike, just get stuck in. E: like seriously I'm not exaggerating, the DRZ400, favorite of dumdums and case cracking cavemen the world over, is a swiss watch spaceship compared to what you've got. This is very much a good thing don't get me wrong, there's just no need for immense caution cause your chances of actually damaging something are so minute. Slavvy fucked around with this message at 23:32 on Jan 8, 2022 |
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Jan 8, 2022 23:29
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At least the 200cc vanvans 2016-18 are EFI (this is an '18). I've got about a gallon in the tank and I haven't learned yet which hose is which on any bike for over a decade (and only 1 before that), so if I do fall back to guess-and-check I want to at least make sure I have a clean fuel can on standby instead of a water bottle so I can pour it back in when I'm done. The CA evap system doesn't help, makes everything more crowded in there. Remy Marathe fucked around with this message at 23:38 on Jan 8, 2022 |
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Jan 8, 2022 23:34
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Ok so if it's EFI it is very unlikely to have any kind of tap or anything like that, it will have a fitting going directly to the pump. Depending on the design this will either gush out fuel, drip slowly or not leak at all. The hose trick is a good solution here as well. You'll need to use your own hose as the EFI pressure bearing kind don't like being folded. For evap stuff, consider using a painted marker or white out. For example if I have three vacuum lines close together, I'll label both the lines and the fittings they go to with 1, 2 or 3 stripes. No need to know what they do or where they go to, just need to keep track of what was plugged into where. Slavvy fucked around with this message at 23:50 on Jan 8, 2022 |
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Jan 8, 2022 23:45
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Okay here's what I think I'm looking at after factoring out the breather/evap system and looking at some more diagrams: 1-One short line from tank to fuel filter, no shutoff, I'm going to have to just rapidly swap in a zip-tied hose to cap this right? 2-The fuel filter has a third mystery output that goes up and crosses the body to a 3-way join, which connects to both the tank and the fuel injector. Still trying to figure out if the section between tank and join will be vapor or fuel, but it looks like it's all a vapor return. Remy Marathe fucked around with this message at 01:20 on Jan 9, 2022 |
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Jan 9, 2022 00:50
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It's hard to picture what you're describing, use the camera in your pocket. The fuel system should go pump/tank > filter > injector > pump/tank if it has a return line. If you have a return line you'll need to cap that off as well as the pressure line. It's very hard to tell from your description if you're talking about a return line or some sort of vapor hose. None of this makes a difference anyway, you don't need to know what they do, you just need to put them back in the right place. I think part of the confusion is you're using 'fuel injector' (a part the size of your little finger) instead of 'throttle body' which is the large cast alloy piece that has the throttle plate, injector, cables etc Slavvy fucked around with this message at 01:57 on Jan 9, 2022 |
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Jan 9, 2022 01:55
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Sorry, not sure if these'll help and not sure how to attach more than one at a time. A) Comes from the fuel tank to the fuel filter B) Continues to what I'm calling the fuel injector C) Is the mystery line X) is the overflow/evap line nobody invited
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Jan 9, 2022 02:51
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This is what I'm calling the fuel injector.
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Jan 9, 2022 02:52
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This next one is on the right side of the bike. EDIT: This pic was mislabeled. The leftmost hose is what crosses over and hits this "T" junction, "C" here is not actually hose C, but rather goes to the FI. The right-hand branch heads into the tank. Remy Marathe fucked around with this message at 01:25 on Jan 10, 2022 |
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Jan 9, 2022 02:54
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4th and last: This is the SM description that seems to indicate this is a vapor return to me. (C) in previous pics corresponds to the line hitting the 3-way split indicated with (1) I also just discovered a page in the SM that describes draining the tank before removal which supersedes my original instructions. You're probably more familiar with this than I am, but this service manual starts out with the basic stuff that applies to most, then provides revisions for various versions each of which say "if unspecified, follow instructions for the previous model". Remy Marathe fucked around with this message at 03:00 on Jan 9, 2022 |
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Jan 9, 2022 02:57
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Ok, I think I see what's going on here. Firstly you have correctly identified the injector, and I also don't blame you for getting a little lost, because that is an absurdly complex system for an air cooled thumper holy poo poo. Having said that, I think what's happening there is you have a return system, which normally means a pipe going from the injector straight back to the tank, but for some reason they decided to plumb it into the fuel filter as well. It's not a system I've ever seen irl. This may be for some emissions related reason like capturing vapour if the bike sits idle with the return line empty, or something of that nature. It looks like your best bet is to disconnect the two hoses coming from the tank to remove it, this would probably create a mess though. At this point if you want to stay mess free, you might need to improvise a line clamp. If you clamp off the two lines coming from the tank, then unhook the bottom-most one on the fuel filter, you'll be able to catch whatever comes out in a cup or whatever. Then just unhook the clamped lines at the bike end and remove the tank. E: now I'm having second thoughts. Is C plugged into the injector or the TB is the million dollar question. If it goes to the injector, it's a return system like I described above. If it goes to the tv, it means that C is a vapour line and they're using the fuel filter as an evap canister or whatever, like it has two chambers inside that do different jobs. In this scenario you just need to clamp off A, remove B from the filter and drain into a cup. C will have nothing in it. Slavvy fucked around with this message at 04:34 on Jan 9, 2022 |
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Jan 9, 2022 04:26
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Thanks for all the info. Confirmed, the 3-way juncture goes into the topside of the fuel injector. My previous pic of the right-hand side was incorrectly labeled; hose "C" from the fuel filter was actually the leftmost line in that picture, and the one I mislabeled "C" was what goes to the FI. A better and corrected pic of that below. If you're curious I can scan the relevant SM diagram but I think I have an idea of how to proceed now, clamping the two tank hoses discussed. This isn't emergency work- checking valve clearance is the last thing left on my 620mi service, and from what I gather it's very unlikely they'll actually need adjusting. It'll have to be next weekend now at the soonest, so if waiting for actual line clamps like you linked (these maybe) will make the job easier or less prone to fuckups I'm all about that. I went backwards page-by-page to find the most specific tank removal instructions and they say to: 1) Drain out fuel 2) Place a rag under the hose joint and disconnect the fuel hose 3) Disconnect the fuel level switch lead wire coupler 4) Remove tank bolts 5) Disconnect the (other?) fuel hose [pic that looks nothing like my bike] Remy Marathe fucked around with this message at 01:28 on Jan 10, 2022 |
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Jan 10, 2022 01:23
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I would get/make some type of line clamps and just leave everything downstream of the two hoses coming from the tank connected. There will be fuel in the filter etc, you could drain that like I described or you could just leave it, the layout implies it would ask just stay trapped in there by gravity alone. Alternatively: it should be possible to reach the exhaust adjuster hole without taking the tank off. If the exhaust clearance is good then the intake is guaranteed to also be good (exhaust valves and rockers etc wear much faster from all the heat they absorb) and you don't need to do anything.
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Jan 10, 2022 01:37
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That's an extremely attractive idea, it did look like I could get at the exhaust valve without pulling the tank.
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Jan 10, 2022 01:47
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Fwiw screw type adjusters are usually designed so that the adjuster wears faster than the valve can recess, so even absolutely savage levels of neglect just result in a really noisy and inefficient engine and not much else, because the clearances loosen with wear. It's only a fatal thing to miss if you've got bucket tappets wherein the clearances get closer over time until the reach zero and you burn a valve. I've never seen tight clearances on an old style rocker arm motor like that which weren't the result of owner error.
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Jan 10, 2022 01:52
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I've recently noticed a high pitched noise on my 2020 Ninja 400 in lower gears at higher RPMs, does this seem like anything unusual? The first few times it happened I thought I'd hit my horn while shifting up or something. I haven't ridden much until recently but don't remember noticing it until now. You can hear it briefly at the start of the video, then at about 2 seconds in as I shift down for the turn, then from 8 seconds on as I roll on the throttle, in 2nd gear around 8-9k RPMs. https://www.youtube.com/watch?v=qDybe09h3i8
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Jan 10, 2022 03:30
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That sounds like either a heat shield or muffler internals that have broken loose, or your engine is on death's door. Also please tell me you were riding like that in order to demonstrate the problem, you don't normally ride like that right? Right 
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Jan 10, 2022 03:45
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RightClickSaveAs posted:I've recently noticed a high pitched noise on my 2020 Ninja 400 in lower gears at higher RPMs, does this seem like anything unusual? The first few times it happened I thought I'd hit my horn while shifting up or something. I haven't ridden much until recently but don't remember noticing it until now. *Might* be something vibrating as the RPM hits its harmonic frequency, but I'd really not be happy riding a bike making a noise like that until I'd tracked it down. Might be time to invest in a mechanic's stethoscope and head off somewhere the noise won't annoy people so you can rev it while standing still to see if you can localise the sound.
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Jan 10, 2022 03:45
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Slavvy posted:That sounds like either a heat shield or muffler internals that have broken loose, or your engine is on death's door. For my riding, I may craft my answer depending on which part of the riding you're talking about, in order to avoid embarassment  But seriously am I in the wrong gear for the turn or doing something else stupid? I am pretty rusty and very slow, also have a new rear tire as the second part of my excuse list. goddamnedtwisto posted:*Might* be something vibrating as the RPM hits its harmonic frequency, but I'd really not be happy riding a bike making a noise like that until I'd tracked it down. Might be time to invest in a mechanic's stethoscope and head off somewhere the noise won't annoy people so you can rev it while standing still to see if you can localise the sound.
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Jan 10, 2022 03:55
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RightClickSaveAs posted:The exhaust is aftermarket Akropovic supposedly installed by the dealer according to the PO, nothing obvious wrong with it but that's my untrained eye. I would be looking very closely at your pipe, you might have a broken muffler spring or a popped rivet or something. For your riding, and keeping in mind I wasn't there and I'm looking at a tiny distorted clip, it seemed like you slowed down to an insane degree for what was ultimately a gentle curve. The speed you were initially going at is what I'd call 'natural' for the turn, you'd barely need to roll off at all, but you downshifted, slowed to what looked like a crawl, and then strained around the bend with the engine revving it's nuts off but not take accelerating or loading the bike at all. Basically don't slow down anywhere near as much, don't downshift, actually lean the bike, synchronize your speed and gear and lean so as to hit the meat of the power as you exit. In general really high revs with gently caress all throttle is counterproductive, if you aren't going to use the power or load the tyre at all then you may as well be in a higher gear and make everything much more relaxed.
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Jan 10, 2022 07:34
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Thanks Slavvy! I'll dig into the muffler as much as I can and find a professional if I have no luck. I was experimenting with doing turns in a RightClickSaveAs fucked around with this message at 15:53 on Jan 10, 2022 |
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Jan 10, 2022 15:16
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RightClickSaveAs posted:Thanks Slavvy! I'll dig into the muffler as much as I can and find a professional if I have no luck. I'm 100% trying to be helpful and not a jerk. You have a gopro. Take it to a big parking lot and record yourself doing figure eights. Record yourself doing panic breaking. Watch the recordings. Figure out what you are doing wrong. Then do it again. Obviously very few people will ever do this but whenever I watch myself and then go and try to fix the thing I see myself doing I always improve more than when I just ride. Even if I'm trying to think about it when I do just ride.
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Jan 10, 2022 16:26
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Add to that, set up a turn in the parking lot. You can bring little cones or chalk or just use some natural markings that exist and practice going through the corner you set up. Malls parking lots are great for this.
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Jan 10, 2022 16:31
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I do need to find a good parking lot, especially now the weather is great and I won't be roasting in even light gear. Setting up a GoPro in a parking light is a pro tip, I've done it before but it's been a while. One of my problems is I did 99% street riding for the first few years of bike owning, and the roads where I'm at are all on a square grid. I got pretty OK at predicting car behavior and stopping quickly when I need to while commuting, but when I get out on the fun roads I feel like a complete beginner.
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Jan 10, 2022 18:41
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How often do you guys go practice in a parking lot? When I just started riding I would almost always go practice in a parking lot for ~15 minutes before heading out, or sometimes practice in a lot is all I would do, but as I got more experience and felt more comfortable I started going less. I still make the effort to go at least every couple months. I actually went yesterday to practice emergency braking as well as full lock turns with as much lean and speed as I could manage. The braking stuff was easy but doing the turns was way harder than I thought it would be. I haven't tried in probably over a year, and back then I didn't try to lean the bike over. I actually basically fell over within the first minute or two (bike didn't hit the ground but probably came within 6"). Here's about as good as I could manage after ~45 minutes. I was getting so dizzy and also apparently nauseous from my own exhaust fumes. As you add more lean the bike starts to fall over, so you have to add more speed, which starts to pull the front tire straight, so you have to add more steering and you want to take away throttle and so on. Definitely something to work on. https://www.youtube.com/watch?v=LRTgH5Ts7bk
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Jan 10, 2022 18:43
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Toe Rag posted:How often do you guys go practice in a parking lot? When I just started riding I would almost always go practice in a parking lot for ~15 minutes before heading out, or sometimes practice in a lot is all I would do, but as I got more experience and felt more comfortable I started going less. I still make the effort to go at least every couple months. Imo you did ok. If you want to regulate your speed in that kind of situation, use the clutch and rear brake, it's impossible to modulate the throttle finely enough in that situation as it's not anywhere near smooth enough even on a small bike. Every time you shut or roll off, two things happen: - all the weight flops onto the front wheel, making the steering heavy and increasing risk of sudden washouts - the bike loses ground clearance. You have more ground clearance on the throttle than off because the rear suspension extends in response to engine torque and makes it possible to lean further, while also putting weight safely on the rear tire. This interacts with rear preload and rebound damping so the amount of standing up you get for a given torque can be adjusted by those means. Again I wasn't there and I'm watching a tiny clip but: you could've gone better by just not altering your speed at all and just keeping everything smooth and steady. Every time you do literally anything other than lean, you're costing yourself time and space as the bike has to sort itself out in response to whatever it is you did. Low speed drill stuff is basically the opposite of fast riding because you want to minimize the pitching as much as possible. Think about how you ride a rigid frame bicycle at low speed, that's what you want to aim for.
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Jan 10, 2022 19:05
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Slavvy posted:- all the weight flops onto the front wheel, making the steering heavy and increasing risk of sudden washouts
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Jan 10, 2022 19:21
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The answer is always everyone needs MORE practice more often. Frequency is really important too, for instance 15 min 3 times a week is preferable to 45 minutes 1 time. Frequency is how you build and keep muscle memory. I always do some practice before I go out and often times when i'm coming home unless i'm time crunched, but I have a really convenient place basically right by my house so i know that's not necessarily feasible for everyone.
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Jan 10, 2022 20:59
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Commutes & familiar runs are also notorious for letting bad habits and weak spots go unchecked because they're predictable 90% of the time and you unconsciously work around them. As I'm relearning, I'm finding I develop much more during free-form weekend rides than the commute. Low-speed I'm not yet remotely comfortable with on this bike yet, so I stop off at a parking lot on the way back from work to do some low-speed figure eights. This usually goes: unconfident & sloppy->unconfident and smooth->confident, dizzy & sloppy, and that's when it's time to continue home. I should be doing some more consistent, planned and repeated panic stop drills instead of the random ones I do when I have a clear view and no cars around. I've been close to highsiding in the past, and the one time on this new bike that I intentionally pushed the rear till it locked, sure enough I did the wrong thing (released it). Wasn't a big deal because it was intentional and therefore didn't lock till I was only going a few mph.
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Jan 10, 2022 21:29
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Just want to emphasize: low speed skills are vital and fundamental but also mostly irrelevant above carpark speeds. You basically need two different bikes - at low speed you need a rigid bicycle that tracks a perfect line, has finger light steering and doesn't seesaw; at high speed you need a bike that dives and squats and squirms and has heavy stable steering. This is impossible so the manufacturers have to compromise; anyone who's tried to ride a race bike at carpark speed will immediately realize how much dynamic capacity has to be compromised away, even on superbikes, to make them useable at suburban speeds. One of the reasons small bikes are learner bikes is because they don't go fast enough to need high speed stability and strong kinetic behavior, so the compromise can be very heavily skewed in favour of low speed stuff. What's hard is transitioning from slow stuff to fast stuff. Imo the absolute key to this is understanding how to use the brake properly and this is simply not taught as far as I can tell. You are taught by rote learning that you brake upright and then release when you're at the right speed for the corner. This is fine and good and will get you through, and it's a very good way to maintain corner speed on small slow bikes, but technology has moved the gently caress on. The right way to use the brake today, on today's bikes and tyres, is inversely to the throttle rule ie maximum braking upright, tapering off as you add lean. Braking into a turn is just a mirror image of accelerating out of one. Once you're able to brake and turn confidently, you now have a totally manual, infinitely adjustable control of front tyre load. If you're just pitching in off the brakes, you're basically stuck with whatever steering geometry the bike has in that situation and relying on the molecular grip (stickiness) of the tyre. Once you've tipped in you are basically totally committed and if something bad happens your only options are to bail out and run wide, or try to lean further and hope you make it. If you brake into the turn however, you are forcing the tyre into the road, creating grip and making the bike dive to speed up the steering, all manually controlled by you, so you can perfectly modulate your front grip and entry speed right to the apex. If something bad happens, you're already braking so you can just stand up a bit and brake more, likewise if the corner tightens you have the option of braking more, or trailing it a bit to make the corner, or releasing to get more lean angle. You just have more control, more options, more feedback as to what the bike is doing.
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Jan 10, 2022 22:28
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Remy Marathe posted:Commutes & familiar runs are also notorious for letting bad habits and weak spots go unchecked because they're predictable 90% of the time and you unconsciously work around them. As I'm relearning, I'm finding I develop much more during free-form weekend rides than the commute. My current commute in particular is incredibly poo poo because it's totally straight the whole way; the one I had 3 years ago was longer and had a lot more motorway, but at least it also had a couple miles of twisties at one end
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Jan 10, 2022 22:49
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You’ve explained this better than the training courses I’ve taken or found on YouTube, so thanks for laying this out. I don’t think anything else I’ve seen has talked about using the fork dive so purposely. The main road near my house I need to take to get most places is 25 mph and has some pretty decent turns in both directions, so I have great places to practice this on my way to a parking lot to practice the other slow speed stuff.
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Jan 11, 2022 00:54
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Geekboy posted:You’ve explained this better than the training courses I’ve taken or found on YouTube, so thanks for laying this out. I don’t think anything else I’ve seen has talked about using the fork dive so purposely. TRAP SPRUNG BINCH! Unfortunately for you, you've decided to learn on a sportster so almost none of that applies! The sporty has an extremely old fashioned, very particular chassis design which is good at dirt track and hill climbing and doing sick drifts, and terrible at everything else. This means the majority of the weight is toward the rear, the frame basically has a hinge in the middle, the steering is very lazy, but most crucially, the bike doesn't respond to trail braking like a normal bike. All you'll achieve by dragging the brake on a sporty is running wide towards the outside, until you run into ground clearance issues. The way to get the best out of that bike (and many other cruisers, but especially Harleys and ESPECIALLY older Harleys) is to keep them on the back wheel as much as possible, by completing your braking in a straight line then getting back in the throttle before you even start to turn, so you navigate the entire corner on the throttle. This raises the bike to the point where you can run much, much faster lines than you could with aggressive trail braking and is the traditional method that's still taught because all the instructors learned on 70's UJM's. All that delicious lumpy low rpm torque, combined with the excellent throttle fidelity of having a small single carb feeding two very large jugs, lets you manage ground clearance and traction using the throttle alone, the front can pretty much do whatever the gently caress it likes cause if you're doing it right it hardly ever gets heavily loaded in the corner. The downside to all this is that it gives you extremely limited options if you went in too fast; your can't shut the throttle because the bike will immediately bottom out and also start pushing wide, you can't brake because you'll fold the front, so standing up and hauling on both stoppers is your only choice. The fat bob and the xr1200 are the only Harleys I've ridden that are capable of meaningful trail braking and, not coincidentally, they have very beefy rigid forks, lots of ground clearance, a chunky front tyre and some effort made to stiffen the chassis. The vrod feels like it could do it too but it lacks the ground clearance to achieve anything in the corner so it's moot.
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Jan 11, 2022 01:47
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I am glad I sprung the trap. I had too long of a day to go on a ride after work, but I’m hoping to tomorrow and will probably read this 4 or 5 times. Do you think this applies to my scooter as well? It certainly feels like I’m putting everything on that back wheel when I really push a corner.
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Jan 11, 2022 02:47
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Geekboy posted:I am glad I sprung the trap. Yes it does, for more prosaic but similar reasons. The scooter is extremely tail heavy because of production necessity, it has the chassis rigidity of a wooden raft because it's too slow to weave, and it has an absolutely garbage, possibly not even telescopic front end combined with a tiny tyre, because nobody cares about scooter handling (there are exceptions to this, glorious exceptions). The only strong suit a scooter has is the rear shock, because of all the weight and the expectation of cargo etc, so keeping it on the throttle as much as you can it's the best way. The technique I described is 100% the way to go if you have a bike which is philosophically from the 70's, which nowadays is pretty much just Harleys, Enfield and scooters. Slavvy fucked around with this message at 02:53 on Jan 11, 2022 |
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Jan 11, 2022 02:51
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Slavvy posted:The way to get the best out of that bike (and many other cruisers, but especially Harleys and ESPECIALLY older Harleys) is to keep them on the back wheel as much as possible, by completing your braking in a straight line then getting back in the throttle before you even start to turn, so you navigate the entire corner on the throttle. This raises the bike to the point where you can run much, much faster lines than you could with aggressive trail braking and is the traditional method that's still taught because all the instructors learned on 70's UJM's. For bikes that do work like this, what constitutes enough acceleration to really add grip? How much speed should I be gaining through the corner to be sure that I have positive loading on the rear suspension and tyre?
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Jan 11, 2022 12:53
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This newfangled trail braking nonsense sounds like magic to me and I won't be doing it if I ever get back onto a bike 
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Jan 11, 2022 12:59
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The way I’m thinking through this, if the optimum speed to go through the turn is x[/], then since I’m on a Harley, my best best is to be sure I’m going x-2 or whatever before I enter the curve so I can accelerate back up to [i]x as I enter so I’m always on that back tire. Am I understanding that correctly?
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Jan 11, 2022 20:20
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Renaissance Robot posted:For bikes that do work like this, what constitutes enough acceleration to really add grip? How much speed should I be gaining through the corner to be sure that I have positive loading on the rear suspension and tyre? You don't need to be accelerating or gaining speed through every corner, commiting to that approach is a good way to die. That's basically the opposite technique, stop-go, where you brake aggressively and run a v-shaped lines, using the bike's mass as a pendulum to create dramatic changes in tyre load. If you're accelerating, you're widening your line as you gain speed, this works for very brief corners like city intersections but is much trickier in long sweepers because you eventually either run out of road or out of grip. Some bikes are designed or set up to be ridden like this (KTM) and they typically require vigorously switching from the brake to the throttle to get the bike to pitch forward or back. Bikes like this tend to be hard to ride efficiently in the classical style, because dramatic pitching behavior + the demand for stability = a setup that will understeer when you aren't braking. This is why imo the 690 feels incredibly fast but irl gets destroyed by the mt07, a bike that is technically 'worse'. We will revisit this. Anyway, weight transfer is independent of how much the bike pitches. Think about a rigid bicycle - it has no suspension at all, it literally can't pitch, but you can definitely still transfer weight forward or back and do stoppies and manuals (well maybe you can I'm still too big a pussy). How much pitch you get for a given input is part and parcel of a bike's design philosophy. Some bikes are super pitchy (motards), others are not (old Ducatis), but they all weight transfer. Think of braking. If you suddenly slam the brakes on, what happens? Front wheel locks, you crash and die. But if you apply them quickly but gradually, the fork and tyre get a chance to compress from the initial weight transfer, at which point you can keep braking at the same intensity, or brake harder, or trail it off. Once you release the brake, the load is gone, if you then change your mind and try to reapply while partially leaned, the grip won't be there and you crash. The important part is the initial transfer of weight forward onto the front tyre, even a small amount of initial braking multiplies the tyre load significantly and makes it possible to brake so hard the bike stoppies. But you aren't obligated to do a stoppie in every corner, the important part is creating that initial load. If you're braking steadily, the bike is basically on the front tyre and the rear is just an outrigger keeping it pointed in the right direction. Now think of the throttle. If you suddenly slam it open, what happens? Rear wheel spins, you crash and die. But if you apply it gradually, the tyre gets a chance to compress from the initial weight transfer, at which point you can roll it on, or keep it steady. Once you shut the throttle, the load is gone, if you change your mind and try to chop it back on again, the grip won't be there and you crash. But you aren't obligated to do a wheelie out of every corner, the important part is the initial transfer. Once you've opened the throttle and the bike has transitioned from one state to another (this takes a fraction of a second), the grip is there and any additional acceleration will just create more grip (within reason and while following the throttle rule ofc). If you're on a steady throttle, the bike is basically sitting on the back tyre and the front is just an outrigger. Notice how I made those paragraphs the same, implying it's exactly the same? Well....almost. The fork will dive in proportion to your braking intensity, this is simple. But the rear shock won't squat in proportion to throttle use. The reason is, bikes have anti squat geometry. This means that the swingarm layout is such that engine torque, when applied, creates a downward pull on the swingarm, causing the bike to get taller in the rear. You can test this by putting the front tyre up against a wall and gently trying to let the clutch out, you'll feel the rear of the bike rise up. What you have to do on cruisers is take advantage of this effect; the difference between a shut throttle and a steady throttle is worth like 10° of lean angle, it makes a huge difference to how far you can lean, which is why you need to be on it before you've even started turning. So to answer your question, you know the grip is there when the bike has transferred from the front to the rear, which is basically just how long it takes for engine torque to pull up the slack the drive line and start torquing the tyre, it's a split second. You certainly don't need to be accelerating, you just need to be on a steady throttle. Accelerating would be counterproductive because it widens your line and forces you to reduce lean angle to avoid crashing. This is where it gets muddy and complicated. The amount of anti squat you get is the result of a bunch of different competing forces: engine torque, bike weight/height/wheelbase, shock spring rate and preload, swingarm jommetry, shock rebound damping, fork rebound damping. So different bikes respond differently, how much initial throttle you need to make the bike stand up can vary. Take our 690 vs mt07 scenario. The 690 is designed to run aggressive stop-go lines and thus needs powerful anti squat force even when accelerating hard. This is great for creating grip when you're donging it up out of a slow turn; you brake hard, park it at the apex, grab a fistful and go (this is why muppet learners love them, makes you feel like you have skill). But if you need to do a long, sweeping turn where constant acceleration isn't possible, you need to be on a steady throttle. There isn't enough torque being generated at small throttle openings to create the necessary anti squat force, at the same time the fork is quite heavily damped to deal with aggressive braking, so overall the bike will basically sit on it's rear end like a chopper and have a poor turn rate for a given lean angle as the front wheel skips and jumps about and the steering geometry stays slack. From the rider's perspective this feels like a bike that just refuses to go where you point it and constantly tries to run you wide unless you lean super far, at which point it feels nervous and skittery and confidence sapping. The mt07 by contrast is a very traditional, very Yamaha bike, designed for corner speed above all else. It doesn't need powerful anti squat, because it's not designed to accelerate like mad from low speed, because if you're doing your job right you never slow down that much in the first place. The priority is maintaining momentum, braking as little as possible, so the bike needs to have as much ground clearance as possible even with relatively small throttle openings. In a long sweeper, the bike will happily go to near-full extension of the rear suspension if set up right, giving you the most possible lean angle and thus the best possible turn rate. At the same time the fork is very supple, allowing the bike to track a tight line even with relatively little front tyre loading. This does hurt performance when braking, but again, you don't need to be trail braking super aggressively because that isn't the right philosophy for the bike. From the rider's perspective, this feels like a bike that's very sensitive to hamfisted inputs, but also turns ridiculously well for a given lean, and gives loads of confidence at high lean angles as the tyres smoothly snake and slither over every little bump. If you raced the two with equal riders, you'd find the KTM wins if you're racing around a city grid or very tight, very bumpy mountain roads, where it can take full advantage of it's aggressive trail braking ability and heavy damping. The mt07 will be much faster everywhere else because it has so much more corner speed and precision. Imo people complaining about fork dive is usually a red flag that they have poor skills, have beer little corner speed and don't understand that the soft, soggy fork is a massive benefit when you're on the throttle. But wait there's more, no don't run away, come back! Anti squat is adjustable! And it interacts with fork rebound damping and I have an incredibly stupid but very illuminating personal anecdote to do with this! Come back...! Slavvy fucked around with this message at 21:20 on Jan 11, 2022 |
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Jan 11, 2022 21:02
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Slavvy posted:Imo you did ok. If you want to regulate your speed in that kind of situation, use the clutch and rear brake, it's impossible to modulate the throttle finely enough in that situation as it's not anywhere near smooth enough even on a small bike. Every time you shut or roll off, two things happen: Normally in slow stuff I do slip the clutch a lot, but in this case I couldn't get it quite right (kept pulling in too much), so once I got the bike tracking I let the clutch out and used the rear brake only to help stabilize it. I was definitely focused on just making the turn as tight as possible whereas I probably should have started wider, got it super smooth, and tightened up from there. Here's a suspension/setup question: I am pretty sure my shock's rebound is too fast. At track when I am at "full lean" and I hit bumps, the rear often steps out. Not huge slides, but enough to take into consideration. The shock is non adjustable besides preload. I feel like if I added on a few turns of preload it would just make it worse. I'm going to get some better tires but I wonder if it would just mask the problem even more until it gets to a point where a slide wouldn't "self recover" because... uh, I don't know? The tire grip exceeds the suspension's road holding ability?
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Jan 11, 2022 21:40
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