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slidebite posted:How often are you changing oil/filters/plugs in your lawnmowers? I have a cheap-n-nasty Champion pushalong with a Chinese Briggs flathead clone engine - I change the oil once per year after the last cut of the autumn and run the fuel tank dry. I take the plug out to see how it looks but I'm treating that as a 'change when it starts running badly' sort of thing. My mum still has a Hayter Harrier pushalong from 1990 with a B&S 3.5 and I'd put money on that still running on the oil I put in it in 2004, and I'm pretty sure the oil that came out then had been in there since it was new. That thing can sit in a shed with a 29-year old plug, 15-year old oil and stale fuel and still fires up on the second pull - once you've primed it by tipping it on its side because it's one of those ones with the tank below the carb but no squeezy plunger bulb.
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Aug 14, 2019 14:54
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| # ¿ May 10, 2024 17:38 |
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Question for the thread: I have an old (30-ish years) Makita portable generator with a 7hp Fuji-Robin engine. I've had it a little under a year and it's worked fine, both electrically and mechanically. The other day I decided to give it a service for the first time in my ownership (so the oil that came out was whatever the last owner put in). A bit dark but not at all sludgy and no swarf or nasties. The sticker on the engine says it takes SAE 30 in the summer and 10w30 in the winter. I had 10w30 mineral oil on the shelf so used that. With the new oil in the engine's low-oil shutoff keeps tripping, even though the oil level is right up to the Max mark (it's one of those engines where you take the reading by unscrewing the dipstick and inserting it back into the hole without screwing it down). In any case, it's a 250-ish cc engine and I've put 0.85 litres of oil in it, and the oil is visible through the dipstick hole so it is by no means dangerously low. The engine has a manual governor with three setting, Idle, Start, and High (you only use it as a generator on High). It will run all day on High (3000rpm) but the oil shutoff will trip after 10-20 seconds of running on Start (approx 1500rpm) or Idle. The oil sensor is piezo-electric where the probe vibrates and generates electrical 'ticks' when not dipped in oil (which otherwise damps out the 'ticks'). The box on the side of the engine counts the 'ticks' and once a certain number are counted it grounds the magneto and stops the engine (and flashes the warning light). I have taken the sensor out of the sump and run the engine with a finger over the end to stop it 'ticking' and it doesn't trip. Remove the finger and after a few seconds the sensor trips and the engine stops. So the sensor is, broadly, working and the oil is the correct grade and amount. But would a modern 10w30 car engine oil (which is what is now in it) be marginally thinner than a machinery oil from the 1980s? Or could something in the blend of even a modern cheap mineral car oil remove its 'damping' properties? Unfortunately I don't have any straight 30-weight oil to swap to and see if that solves it, and I drained the old oil into a rather dirty pan so I don't want to pour that back in and see if that solves it. In the interests of experiment I'm going to get a lawnmower-specific 10w30 and a bottle of straight SAE30 and try that if the multigrade still causes the shutoff to trip. And if the single-grade oil still doesn't solve it I'll assume that the sensor is faulty and that the previous owner put 20w50 or something in there! None of this is a vital concern. I'm sure oil sensors for 1980s Robin engines are now unobtanium and I can just bypass the sensor (it doesn't burn or leak any oil and it's not like I leave it unattended for hours running my house - I use it for power tools in the garden/garage beyond the reach of extension cables) but I'd be interested in any thoughts or experiences. Pictures for interest:  
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Apr 26, 2020 13:47
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Thanks for the responses, people. Pretty much as I thought, but I have an update:sharkytm posted:10w30 and 30w are going to be the same weight in warm weather. Different blends have the same (or close enough) viscosities. Don't put anything fancy in an old generator. Cheap Dino oil is what it was designed for. Yesterday I did exactly that - bought some cheap SAE30 mineral oil from the local DIY/tool repair place. Intended specifically for lawnmowers, generators and other small portable plant. This morning I went to swap the oil and had the same idea you did; while I ran the engine up to warm the oil I had the sensor out of the sump and sitting in the open bottle of new oil. It ran like that without a hitch for 10 minutes.  Testing the probe in the cheap oil. All good. Success, I thought! So I swapped the oil, warmed up the engine for a few minutes at the fast idle then ran it at operating speed with a 2000W heat gun plugged into it. All fine.  240V and no oil warning light - as it should be! Then I did what I usually do before I put the genny away in the shed and ran it at the fast idle with the fuel tap shut to cool down and empty the fuel line/carb bowl. After a couple of minutes running like that...the oil shutoff tripped. I started it up again and after 10 seconds it tripped again. I checked the oil level on the dipstick and the oil was all foamy - this was not the case when I checked the level immediately after a run before, when it was tripping with the 10w30 in it. So the oil doesn't necessarily foam in normal use.  Here's the dipstick as used to check the level. As you can see the level reaches the bottom of the hatched 'Max' mark, so while it could be a few mm higher it's by no means low and it's certainly not overfilled.  Here's a view down the dipstick hole - foamy! I let the genny sit for an hour and checked the oil again - same level and the foam had dispersed. Gave it a test run. It will run and run at the normal speed, and will tick over happily at idle but once the oil is hot the shutdown will trip after about 10 seconds of running at the middle speed. And the oil is foamy again. Surely even a cheap oil isn't going to foam when used in a simple engine at the correct level? I'm more perplexed by this as a diagnostic exercise than frustrated - as I said it's not like I use the generator much, and then not for anything vital. But it does bug me that it was working perfectly before my well-intentioned service, and that as someone who likes to think of themselves as mechanically knowledgeable and adept I've managed to make things worse by doing a straight oil change on a simple single-cylinder flathead engine! The fact that the shutoff doesn't trip at idle or operating speed makes me suspect that the probe or the control box is faulty in some way, although the foamy oil obviously isn't ideal. So, as much as my perfectionist side doesn't like it, I'll probably put the 10w30 which didn't foam back in and bypass the sensor.
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Apr 29, 2020 16:39
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TrueChaos posted:Are you sure it's not overfilled with oil? It'll foam if there's too much, because the crankshaft is whipping around in the top of the oil. I'm as sure as I can be - I'm pretty sure I'm using and reading the dipstick properly (unscrew it, wipe it, put it back in the hole without screwing it down, take the reading) and the engine ran fine with no sign of foaming with the oil at the same mark on the stick, measured the same way, before I started dicking around with changing the oil. Edit: In case I'm missing something obvious, here's the sticker on how to check the oil level:  I don't have the handbook for the genset and the placard on the engine doesn't give the required quantity. I did find an online version of the manual for the next-later version of my generator, using a later model of the same engine and that says it takes 1.0 litre of oil. I have put approx 0.8 litres into the engine to get just below the Max mark on the stick. I did think I could drain some of the oil out so it was 1/3 or 1/2 on the stick, which would be safe to run for a test and see if it still foams and/or trips. Preventative maintenance on small machines seems really overrated sometimes - why can't I be one of those people happy to leave stuff well alone until it breaks? 
BalloonFish fucked around with this message at 17:55 on Apr 29, 2020 |
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Apr 29, 2020 17:43
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angryrobots posted:When you initially serviced it and used oil you had "on the shelf" was it something that had been opened for some time, where it could possibly be contaminated with condensation? It was a bottle of simple 10w30 mineral oil I bought last year for topping up one of my old cars but never used. It was unopened and to put it in the generator I had to break the foil seal. So I don't think contamination is the cause. BalloonFish fucked around with this message at 17:58 on Apr 29, 2020 |
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Apr 29, 2020 17:55
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My generator mystery is resolved - but not in a very satisfactory way. I spent this morning on another go at this. The genny still has the cheap SAE30 in it which foamed. Checked the oil level - no foam, just below Max level on the stick. Started the engine, ran it at fast idle for a couple of minutes, shut it down, checked the dipstick - little bubbles in the oil. Started it back up, it ran for 2-3 minutes more, the oil shutoff tripped. Check the dipstick - loads of foam. I decided that all this oil was doing was creating another problem, so I decided to go back to the 10w30 which only had problem of tripping the shutoff. Before I did so I popped the oil sensor probe in the can of 10w30, and it ran happily for 5 minutes, so the sensor 'likes' the oil in that sense. I drained the cheap SAE30 out (it came out with a foamy head like a badly-poured lager!) and put in the 10w30. I opted for absolute best practise, just in case - I left the probe out of the sump while I filled, just in case there was an air bubble getting under the probe or something. Filled the sump with the 10w30 to about three-quarters full on the stick, fired up the engine. It ran for about 5 minutes and then the oil sensor tripped. I checked the dipstick - no signs of foam whatsoever on either the stick or in the oil visible through the hole. I topped up the sump to dead on the Max mark on the stick, just in case that was it (unlikely at this stage). As I did so I thought to check the wires going into and out of the oil sensor, in case there was a bad connection or a damaged insulation causing a ground or some sort of errant signal. Nothing visible there, and I checked and prodded the bullet connections. None seemed loose. Started up the engine again, and it ran and ran and ran! I have no idea why, since it's now in exactly the same state as it was when I'd done the original oil change (a full sump of 10w30). I can only guess that there was/is a slightly dodgy connection or a little bit of broken or worn insulation on one of the wires and when I did the original oil change I had joggled something close to some other wire or surface so it was shorting/'ticking' with the vibration of the engine when it was running at the fast idle speed, which is why it wouldn't trip if run at idle or full speed. I started and stopped it a few times, checked the oil for level and signs of foaming (spot on the Max mark and zero foaming), then left it running at fast idle for 25 minutes until it used up what was left in the fuel tank. So that's a result of sorts, although it's annoying not to find a specific problem. But even better to have it gone! And clearly that cheap SAE30 I bought from the local DIY shop ("Specially formulated oil suitable for 4-stroke lawn mowers, stationary engines and generators. Contains special high performance additive for prolonging engine life") is utter poo poo and foams when used in engines with splash lubrication...
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May 1, 2020 16:05
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opengl128 posted:Any pro tips on setting the low/high mixture screws on a 2 cycle? Trash picked a 25cc Craftsman blower which looks like it got curbed for gummed up/disintegrating fuel lines (thanks ethanol). Was going to just order new lines but the air filter was soaked too and I also needed a fuel filter/sinker, and it was cheaper to buy a whole carb kit with all of the above plus a new carb and plug and some other bits and pieces. Anyway, got it running but its badly in need of adjustment. Stumbles a bunch, only really stays running on half choke and wants to die when I give it throttle unless I do it really gradually. Just waiting on the screwdriver so I can adjust it (sorry not sorry EPA). It sounds like it's running too lean (hence why it needs the choke and suddenly opening the throttle plate kills it). When setting carbs I've always favoured just running both screws all the way in (gently so as not to squash the tips) then backing them both out one full turn, so you'll be in the zone where it will run but almost certainly too rich. Let it run for a minute to get up to temperature then ease out the low-speed screw (usually less than a quarter of a turn) until you get the smoothest running or the fastest idle - some engines, especially two-strokes, seem to rise slightly in idle as they approach the ideal slow mixture then fall off as it goes too lean. Do the same with the high-speed screw with the engine running on full throttle - slowly unscrew it until you get the smoothest/fastest running. Ideally you should then run it in a tiny bit so it's just slightly on the rich side. You should then get an engine that idles smoothly, runs well at full speed and doesn't stumble when going between the two. If it does then open out the low-speed jet a little or raise the idle speed a bit. opengl128 posted:Yes I've been watching a lot of mustie1. Same: I've been using lockdown to work through his back catalogue so now feel like I know how to spot sick VW engines at 10 paces.
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May 21, 2020 20:01
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| # ¿ May 10, 2024 17:38 |
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For those that remember my Robin/Makita generator from a page or so back, with its problems with the automatic low-oil shutoff system tripping even with a full sump of fresh oil - It seemed to have gone away and I chalked it up to a bad electrical contact/erratic ground. Which wasn't very satisfying but seemed the only explanation. Then the problem resurfaced. After more thought, and remembering that one of the oils I tried kept foaming when the engine was running, even though the oil was within the limits on the dipstick, I drained the sump and refilled it to just a hair above the 'Min' mark on the stick. Everything worked fine - the shutoff didn't trip, regardless of engine speed or temperature and the oil didn't foam. I gradually added oil until it was at about the 2/3 point on the dipstick (measured, in accordance with the diagram on the sticker on the generator's frame, by unscrewing the dipstick, wiping it clean and re-dipping it without screwing it in). All still good. Then I wondered what that oil level would be if you checked it on the stick after just unscrewing it from the crankcase - the answer is that it is nearly bang on the 'Max' mark. So I think that the diagram is either misleading or simply incorrect, and you're supposed to check the level with the dipstick fully screwed in. With the oil topped up (actually overfilled) measured the other way, the oil was either foaming or cavitating at certain engine speeds, exposing the level sensor probe and tripping the shutoff. This would explain why this issue only surfaced after I'd serviced the engine for the first time in my ownership - it always had 'enough' oil on the stick when I checked it the wrong way, but when I refilled it with fresh oil up to the mark I was actually overfilling it. It would also explain why that oil foamed (I guess the other couple I tried were made of tougher stuff and didn't aerate so easily). This is the peril of not having the right handbook for machinery. I don't know what the sump capacity is (it doesn't say on the info plate on the engine) and I don't know the proper dipstick technique. There are manuals online for later Makita gennys with later Robin engines and they clearly say to check the level without screwing the dipstick in, which since that agrees with what the diagram seems to say so that's what I did. But I wonder if Robin changed the measuring method and the older engines should be dipped with the stick screwed in.  (Here's the diagram again, for reference) But in anycase, it now runs perfectly and there's either a full sump of oil (if the measure is with the stick screwed in) or a 2/3-full if it's done with the stick unscrewed, so I'm leaving it at that. slidebite posted:What's the deal with multigrade oil and small engines? The Honda gx270 powered compressor I just bought and going through recommends against multigrade oil in the owner's manual I found online and only straight sae30. I typically run 5/10w30 in my small engine stuff. My understanding of it was that the viscosity improvers in early multigrade oils didn't cope well with the conditions found in a lot of small engines. An old 10W30 was an SAE10 blended with viscosity improvers so it didn't thin out at running temperatures. These VIs broke down at the high oil temps and especially the hot spots around the exhaust valve often found in hard-worked small air-cooled engines with rather primitive cooling arrangements and no dedicated oil cooler. The VIs would turn to varnish, which clogged up the internals and as they degraded the oil would gradually turn back to the straight SAE10, which didn't provide adequate lubrication. At lower ambient temperatures the overall oil temperature would be lower and the lesser viscosity of the multigrade was needed to ensure easy starting and good lubrication until the engine got up to temperature. So for ages the recommendation was plain SAE30 for everything except wintery near-freezing-and-below ambient temperatures, when the 10W30 was acceptable. Modern oils with fancier chemistry cope much better with high internal temperatures so there's no problem using a multigrade. Many more modern small engines have full-pressure lubrication with a pump and a filter, and some even have things like hydraulic valve lifters which not only allow for the use of a mulitgrade oil but virtually require it. I believe there are emissions factors at work too - specifying a 5W30 oil allows for faster cranking speeds, faster starting and better cold running, all of which helps get an engine through those bits of the emissions tests.
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Aug 17, 2020 11:14
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