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Speaking of repair stands and chains, I got a motorcycle with a single side swing arm which I don't have a stand for. Snagged this roller thing off Amazon for $30: https://www.amazon.com/gp/product/B07PKQPLC3/ and it actually works super great. Easy to back onto it. Easy to spin the rear wheel while sitting down by the chain and cleaning it. The rear wheel did kind of want to wander off it. Had to push or pull the rear wheel while I was spinning it. Still super easy to do with one hand. Also had to put a few blocks under the kickstand to keep the bike fairly vertical.
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Sep 1, 2021 00:32
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| # ? Jun 8, 2024 12:31 |
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Jim Silly-Balls posted:Not a lot of motorcycle discussion happening here….. I'll steer this thread back to the motorized bicycle by doing an effort post I've been meaning to for a while. We're going to learn about engines. Warning: painful wall of text incoming. There's a lot of talk about engines and their nature, especially the esoteric details that don't matter in cars and such, but matter a great deal on bikes. Things like vee angle, firing order and so on loom large in people's minds but are really pretty secondary characteristics. Additionally, marketing has created a fixation on technical details (DOHC! Crossplane!) when in reality, like every part of a bike, the bedrock is philosophy and the technical details are just tools to support that. It starts with the needs of the meatsack riding the bike and ends with gear driven v4's, not the other way around. What is an engine, actually? You can answer this in different ways but for our purposes, an engine is two somewhat separate things: an air compressor and a furnace. The furnace is the combustion chamber. The compressed fuel/air mix is lit by the spark plug, the flame front advances outwards and pushes the piston away, creating torque. Easy, but tells us nothing about the nature of the engine; combustion efficiency determines torque output for a given cc and fuel efficiency and that's about it. This is why tq:cc is on a steady upwards march through the decades as the combination chamber gets more refined. The air compressor is where all the action is. In a four stroke, the compressor is formed by the piston and the valvetrain. The piston moving downwards creates a vacuum, the valves opening and closing allow air to be drawn in then trapped for compression. The details of this process are what determines the fundamental character of the engine and everything else is designed to support the result. Torque Not only a terrible movie, but also the way we measure engine output. Power is a maths equation (TQ x RPM), torque is tangible. Torque and where and how it happens is what you feel when you open the throttle, it's what determines the ideal lines the bike can run, how big the rear tyre needs to be, the geometry and suspension tuning of the bike, basically everything. So let's build a bike. Not an engine, a whole motorcycle, we'll call our brand gooncycles. We'll stick to a single cylinder four stroke for now. Our men in white coats have already developed an excellent combustion chamber that burns efficiently in a variety of circumstances and makes a competitive amount of torque, it's good for 20,000rpm because half our budget was spent on hiring a Honda engineer; gooncycles is closer to hyosung than royal enfield. We can do anything we like. What do we do then? The big question What's this thing for? You don't just build a bike after all, you build bikes for task. And every task needs a different engine character. Gooncycles needs a model range! Are we building a trail bike? If so, we need lots of torque off the bottom for chugging up sandy slopes and a reasonable spread of power for the open stuff. Touring bike? We need midrange. We need a broad, powerful punch that lets us overtake cars with goonspouse on the back and panniers bulging with funkopops. Sport bike? We want team goonrace to be competitive, we need to make the most possible power on straights, so we use as much of that 20,000rpm as we can (tq x RPM!); bottom end torque isn't really a concern cause you only start the race once and generally don't go slow. All of these are very different requirements, but all hinge on a single component: The camshaft The camshaft is what determines where our torque happens in the rpm range. We judge cams by the metrics of lift and duration. Lift is just how physically far the valves open into the combustion chamber, this is a concern for people modifying older engines but our HRC engineer has ensured it isn't going to be a problem and we can run optimal lift, as allowed by our cylinder geometry, at all times. Duration is how long the valves are open, this is where the magic happens. We need to match our duration to our intended use. We want the intake valve to open right as the piston reaches top dead center and shut pretty much when it hits bottom, with the exhaust valve opening shortly after. When the piston nears tdc, the exhaust valve shuts, but only after the intake valve has opened slightly, so both valves are open simultaneously for a moment. This is called overlap. Overlap helps us because the incoming air charge, compared to the speed of the piston and valves, is basically a goopy slug of jelly with a lot of momentum built up from it's rush down the intake tract. We want to preserve this momentum as long as we can so we can get the maximum amount of mixture into the cylinder and take advantage of our efficient combustion chamber. Keeping the exhaust valve open slightly creates a sort of suction effect where the departing, expanding exhaust gases escaping through the exhaust valve help pull the incoming charge into the cylinder. The problem is, the ideal duration and overlap are dependant on rpm; if we have lots of overlap at low rpm, there's too much time for fresh charge to escape out of the exhaust and efficiency is lost, if we have insufficient overlap and duration at high rpm there isn't enough time to fill the cylinder fully and efficiency is lost. You can see that in every dyno chart, there's a bulge or plateau where lots of torque is developed, with not a lot going on either side. The torque curve may as well be an air pump efficiency curve because it's determined almost entirely by how much duration and overlap the cams have. We can put the bulge anywhere we want in the rpm range, but you find that as you move up in rpm and the overlap and duration increase, the efficiency loss at low rpm also increases. So torque can either start early, be fairly broad and drop off at high revs (when the short duration starts to choke the flow), or it can start late and go to a very high peak (when flow from lots of overlap is at it's most efficient) with an inefficient hole down low. Real life Let's start with our trail bike, the dirtgoon 250. We need low range torque, so we're going to have a short duration, low overlap cam designed to fill the cylinder as efficiently as possible over a fairly long period of time, because the piston is moving fairly slowly. Supporting this, we want to maximize intake charge momentum, so we'll have a relatively short, narrow intake port, because squeezing the air through a narrow passage tends to make it speed up aka the venturi effect. So we only need one fairly small intake valve. We're spinning slowly so we aren't pumping huge amounts of gas out the back, so the exhaust can also have one fairly small valve. Two valves mean we can run one central camshaft easily aka SOHC. A two valve head also leaves lots of spare volume of metal for absorbing heat, and we're spinning slowly anyway, and the bike needs to be rugged and handy on tight trails so we may as well make the whole thing air cooled. Job done. Note that all dirt bikes IRL are singles. Now we have to develop the touring adventure bike, the goonglide XXL. We need a bit more grunt in the midrange, so we increase duration, because the piston is moving faster so we have less time to fill the cylinder. We also want a bit more power so we need more exhaust scavenging and thus, more overlap. Our off-idle performance suffers but that's no big deal and a worthwhile trade for passing power. Now our previously helpful intake port is too small to flow sufficiently at higher rpm, so we have to make it and the valve bigger so we can cram enough charge in there within the reduced time available. The intake tract needs to be a bit longer because the higher revs means it needs more time to build up momentum so we give it a longer water slide, as it were. Eventually we hit a point of diminishing returns where the valve becomes too physically large, limiting lift and endangering reliability just from the physical effort of controlling such a big heavy lump of steel. So we move to two smaller intake valves; port area and therefore air throughput is increased, while the valve mass decreases and lift can remain within our physical constraints. We might as well move to two exhaust valves as well to get the most out of this extra flow, and now things have become so crowded that operating them with a single cam isn't ideal (this did not stop Honda btw), so we move to two separate camshafts, one for intake and one for exhaust aka DOHC. All this creates a lot of extra heat, and combined with traffic use and meatsack comfort, pushes us into the complexity and bulk of liquid cooling. Meatsack feedback tells us our big thumper is unpleasant and unrefined at speed, owing to the great big piston flapping about, so we halve the cylinder capacity and double them up to make a parallel twin. This has the benefit of improving reliability at high rpm because smaller, lighter moving parts create less strain on our oiling system and mechanical parts. At the same time, service intervals can be relaxed because the work done by each cylinder is halved with a corresponding reduction in wear and tear. Note that basically all ADV bikes worth a drat are twins. Now we come to the sport bike, the goonsport 1000F (for fail). This is where it gets really complicated, because there are lots of ways to skin the cat. Naturally we need big power so we need lots of duration and overlap coupled to high rpm, as well as a short wide intake tract to fill the cylinder quickly, but what kind of power do we want? Again, philosophy. You can ride a sport bike in one of two ways (it's really a spectrum with two extremes), stop-go or corner speed. Stop-go involves braking late and deep into the corner, getting the bike pivoted at the apex, then stranding it up and using the exit as a curving drag strip to maximize acceleration onto the straight, effectively running a V shaped line. For this you need big power, good upright traction and excellent stability under braking. The epitome of this approach is motards, the h2, 500 GP bikes, that sort of thing. Corner speed uses classic, wide sweeping lines by braking early and opening the throttle as soon as possible to generate gentle acceleration through the whole corner. This is how you're taught to ride, it's epitomised by 125s and other small bikes, as well as 600's like the r6 and other handling-over-power bikes. If we're doing stop-go, we should go for maximum power. Loads of overlap, concentrate all the torque right at the top. Yes, managing this will be difficult for the rider but that's what he's paid for, and if it spins and wheelies it'll do it when the bike is mostly upright so nbd. We have to build a strong, rigid chassis that can cope with the immense loads of hard trail braking and big sudden power, and the bike has to be comparatively tall, creating weight transfer to generate the necessary grip. All of these things make the bike corner worse, but we consider it worthwhile. The best way to go about this? An inline four cylinder, they are very smooth at high revs and physically strong enough to make big power. Yes they're wide and bulky and slow the bike's roll rate, yes they're hard to control on the edge of traction because the power pulses are so close together, but who cares we want power. If we're doing corner speed, we still need competitive power but it needs to be coupled with control, because we expect the rider to gently feed it in gradually while the bike is leaned over. The problem with maximizing power is that it makes the torque bulge relatively narrow and the bike's throttle response really snatchy, as well as restricting the rider to exacting line and gear combinations to avoid falling out of the useable zone. So we dial it back a bit, make a little less power than we could, make the torque spread broader, the engine friendlier. Because we aren't chasing power but control, we should go for a v-twin. The engine is narrow and long, which helps with the kind of long and low geometry we need for high corner speed. The power delivery is lumpy, which helps with on-edge traction, and the whole thing is lighter. We have to carefully tune the chassis to be supple and flexible at lean to maximize precision and side grip. V-twins have trouble revving high reliably, but that's ok because we aren't chasing big power. The balance of power between these two approaches ebbs and flows with tyre development, if you want to watch it happen in real time I highly recommend motogp. Everything on the bike exists to get the most out of everything else, the engine is our fundamental starting point because of the cost and complexity but it's all a big holistic circle. Change one thing and you create ripple effects across the rest of the bike. So again, our absolute bedrock is philosophy, not engineering. Stuff that bears further consideration but would make an already unbearably long post longer: What effect do bore/stroke changes have? Whither the v4 and inline triple, whither the crossplane crank and narrow angle vee? What about variable valve timing and variable intake systems?
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Sep 1, 2021 01:52
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dang, how can I fit one of those on my bicycle?
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Sep 1, 2021 02:15
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There are very serious errors in Slavvy's writeup, namely that Torque is actually a fantastic movie
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Sep 1, 2021 03:34
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Dang. Almost feel like I understood that. Going to reread tomorrow with less alcohol in my system and more caffeine.
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Sep 1, 2021 04:55
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I wish it was easier to try different motorcycles. I've been trying to find local demo days to no success.
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Sep 1, 2021 07:21
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I've been shocked at the number of nice bikes I've seen on whatever that bike rental app is, that's probably the easiest way to try them out and really get a good feel.
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Sep 1, 2021 07:36
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MomJeans420 posted:I've been shocked at the number of nice bikes I've seen on whatever that bike rental app is, that's probably the easiest way to try them out and really get a good feel. Was it you that was looking at a Hypermotard before? Did you try one yet?
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Sep 1, 2021 09:50
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Slavvy posted:So again, our absolute bedrock is philosophy, not engineering. Finally an admission that funny front ends are good, actually so long as your philosophy is building a bike that looks  But seriously, nice effortpost 
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Sep 1, 2021 10:55
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Rev. Dr. Moses P. Lester posted:There are very serious errors in Slavvy's writeup, namely that Torque is actually a fantastic movie  https://www.youtube.com/watch?v=oKkF0xdrz1A
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Sep 1, 2021 12:40
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Oh god. That must have been SO much fun for the actors, if they were allowed to not take it seriously. Also, christ. A jet bike makes a really awesome sound. Why overdub it with some random sound that's objectively much worse than the bike's own sound?
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Sep 1, 2021 16:32
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LimaBiker posted:Oh god. That must have been SO much fun for the actors, if they were allowed to not take it seriously. Because a lot of "hollywood" sound is just get it "close enough"... Also see "Yes Man" with Jim Carey where he rides a Hypermotard and the engine noise switches back and forth between 4-cyl and 2-cyl depending on the shot.
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Sep 1, 2021 17:02
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Skreemer posted:Because a lot of "hollywood" sound is just get it "close enough"... Also see "Yes Man" with Jim Carey where he rides a Hypermotard and the engine noise switches back and forth between 4-cyl and 2-cyl depending on the shot. It's that, and also the fact that ambient sound is always overdubbed because it's easier to do that than film another take because a seagull squawked at an inopportune moment.
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Sep 1, 2021 17:09
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LimaBiker posted:Oh god. That must have been SO much fun for the actors, if they were allowed to not take it seriously. If they used the diegetic sound, every time they jumped the bikes you'd hear the braaaaps from the dirt bikes wearing sportbike plastics that they used in those shots Also lol I forgot how good/bad that was, that's some Bollywood level action
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Sep 1, 2021 17:10
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Phy posted:Also lol I forgot how good/bad that was, that's some Bollywood level action One time I went to see a Kurosawa film, but I guess I missed the last day, and it was replaced with a Nollywood documentary. It was a wild time I tell you what.
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Sep 1, 2021 18:16
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My buddy wrecked his Katana 750 😔 I wish my friends were a bit more careful. He didn't share any details but he does whip around. He lived. Just got banged up. No broken bones. Crank case cracked, magneto cover cracked. Glad I got to try it before it was ruined. It was a nice bike.
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Sep 1, 2021 18:53
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SSH IT ZOMBIE posted:My buddy wrecked his Katana 750 quote:It was a nice bike. 
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Sep 1, 2021 20:04
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knox_harrington posted:Was it you that was looking at a Hypermotard before? Did you try one yet? Yep, and not yet. I've been out of town for work since July, and the used one I was looking at just sold when I checked it today (was not sold a week ago). In a cruel twist of fate my left hand is mostly healed and pretty functional but something about temporary desk setup at work has given me carpal tunnel in my right hand, so hopefully that goes away when I'm done with work. I think come mid-October I'll have nothing to do for a few months so I'm hoping to buy a bike and ride it all day, and finally make some progress on my project bike. Maybe I just say screw it and get a used air cooled hypermotard and hope the maintenance isn't insane. I may rent one from one of those bike share apps as I have a feeling a 10 minute test ride won't give me enough of an idea for how it really is day to day. Every time I get on a DRZ it always feels pretty weird compared to a sport bike at first, at least for me.
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Sep 1, 2021 21:21
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Or every movie where the actor rides a four stroke dirt bike and they dub two stroke sounds over it. Looking at you, Terminator 2 
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Sep 2, 2021 00:38
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Jim Silly-Balls posted:Or every movie where the actor rides a four stroke dirt bike and they dub two stroke sounds over it. I had to go back and check cause I thought that thing was a 2t 80 of some kind but it appears to be a ttr I think?
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Sep 2, 2021 00:41
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XR80 if memory serves E: definitely an XR, you can see it on the seat, maybe a 100? 
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Sep 2, 2021 00:46
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That clip both reminded me that Static-X existed, AND the lead singer died days before his 49th birthday. In 2014
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Sep 2, 2021 00:54
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Carteret posted:Static-X existed Well there goes my country-western binge. nu-Metal here we come!
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Sep 2, 2021 10:18
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Best movie motorcycle sounds: https://www.youtube.com/watch?v=N_NhRm_zS5U
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Sep 2, 2021 21:02
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I want an electric XR now
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Sep 2, 2021 21:10
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"This thing's quiet!"  *GRRRRRRAAAAAAAAAA*
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Sep 2, 2021 21:12
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poo poo, that time of year where wearing the mesh jacket out in the afternoon only to regret it four hours later on your ride home came extra early this year. Not even the windproof lining helped this time around. Definitely felt like a meat popsicle 45 minutes into my ride home. It didn’t help that I had forgotten to wear my clear visor so I had to ride with that up too. Just a combination of bad planning all around, but I wasn’t really expecting to be out late.
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Sep 3, 2021 03:18
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Yeah September is wild. I didn’t get my bike back yet but walking into work yesterday morning I definitely needed a jacket. On some good news though I’m getting my baby back Saturday. Definitely gonna ride in all next week. I need my fix.
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Sep 3, 2021 10:57
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I saw these when I was out running this afternoon  Up at a little park by lake Como that has a monument to Italian motorcycle sport. Nice spot.
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Sep 3, 2021 17:57
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I'm extremely jealous you're riding around Lake Como
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Sep 3, 2021 19:31
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I just spent a few weeks in Europe and saw a bunch of Bullit motorcycles, something I’d never heard of being from  What’s their deal? They look cool.
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Sep 3, 2021 20:09
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All of their models are 250s and 125s, so I assume its a badge engineered china bike.
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Sep 3, 2021 20:17
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knox_harrington posted:I saw these when I was out running this afternoon
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Sep 3, 2021 20:20
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Carteret posted:All of their models are 250s and 125s, so I assume its a badge engineered china bike. It's a Belgian brand. Can't say for sure where they're made - some people claim china, some people claim india. They say they're designed in Belgium too, but i think it's safe to assume that the mechanical bits are just 'standard' parts, which is why they are quite cheap. My local Royal Enfield dealer used to sell them.
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Sep 3, 2021 20:21
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Oh, ok nice. On the subject of small Europe bikes I haven’t heard of, I ran across an FB Mondial 125 in Paris. Not sure on the details other than it’s Italian and I love how it looks.   I also saw a Yamaha R125 in Spain and it looked awesome.
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Sep 3, 2021 20:57
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Boy howdy that is a bunch of different aesthetics going on there.
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Sep 3, 2021 20:58
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That is a very confused young motorcycle still trying to find itself in a complicated world
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Sep 3, 2021 21:22
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It’s a vintage cafe sport scrambler! It’s great!
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Sep 3, 2021 21:23
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Yeah that bike is...something. Everywhere I look it's different and jarring. It's like seeing the Dodge Stratus headlights on UPS trucks, but everywhere. I want to say there are pieces of it I like, but then the thing right beside it resets my brain. Objectively good looking tank and side fairing hiding a weird wimpy scooter motor inside Scrambler pipes but they're mounted way too far forwards like they're just glued on A tiny fender in a place that doesn't matter because the seat sticks out way past it, and another plate/fender mount that looks like how you'd attach a bicycle rack Attractive front end at first, but then it's a 125 so the proportions are all wrong and the bar grips and accessories look huge and goofy. Look at the size of the allen bolt on the mirror mount it's just super weird
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Sep 3, 2021 21:39
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| # ? Jun 8, 2024 12:31 |
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Which exhaust pipe is fake since it's a single cylinder?
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Sep 3, 2021 21:50
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