[quote=“Ducked”][quote=“redwagon”][quote=“Ducked”]
OK, if an air leak won’t produce smoke by leaning, er…how does it produce smoke?
[/quote]
Misfiring, incomplete combustion, abnormally high exhaust temperatures burning off carbon in the exhaust.[/quote]
Caused by? Those symptoms sound like they could be caused by leaning, which you’ve already excluded above, at least in the context of a crankshaft seal leak.
If they aren’t caused by leaning, what are they caused by?
I can’t think of any other effect of an air leak except maybe a reduction in vacuum, perhaps leading to fuelling problems and, er…leaning.[/quote]
Air leaks are unstable and unpredictable causes of leaning, often intermittent and quite extreme. Effects are therefore not quite the same as the carb being set too lean, dirty jets etc.
What Stian describes as dieseling is perhaps 4-stroking? Cylinder fires every other stroke due to number of reasons. One is that the mixture is just too lean to support combustion on each cycle but the unscavenged mixture left in the cylinder on the misfire stroke makes the next one rich enough to ignite. This happens normally in 2-strokes just at the light-load cruise throttle position, but also under more load where there are air leaks or lean condition caused by carb malfunction or in some cases extreme lean settings. This can cause smoke because the unburned oil is still in the exhaust when it’s ignited by the hot gas from the cylinder. Since it’s already dropped a lot in temperature it only burns partially and therefore a lot of smoke is created.
Ed, I may have too quick to dismiss carb leaning as a cause of white smoke and that’s leading you into this either / or thinking. It is pretty hard to create this situation in a motor in the absence of other problems. I usually see it in bikes with air leaks of some sort, or serious ignition malfunction like hideously incorrect timing, extremely low ignition voltage, very dirty plugs etc. Normally where the carb settings are just too lean, it’s a fairly steady state. There is a lot of heat in the exhaust and that keeps the carbon deposits at bay and you don’t see more than normal smoke. In fact you may see less. It’s when the leaks suddenly start or jets suddenly get blocked that these symptoms are the most apparent. Actually the best state for a 2-stroke is a mixture setting that’s just a little too lean. The more heat there is in the exhaust the more energy there in the gas and the better the expansion chamber works. Oil burns cleaner and keeps the exhaust unclogged. Unfortunately you are usually then just a whisker away from detonation and damage to the pistons due to excessive heat. This is one reason race motors have to be rebuilt so often…
I take apart our 13 year old 50cc and cleaned it inside out. Took me 3 weekends to do it. It used to smoke a little and after stopping at red light a little more smoke. Right now after cleaning, it is working like a 4 stroke, no smoke at all. Actually i am scared why there is no smoke at all.
I put everything as it was and it is still using oil as it used to but where did the smoke go?
[quote=“redwagon”] Air leaks are unstable and unpredictable causes of leaning, often intermittent and quite extreme. Effects are therefore not quite the same as the carb being set too lean, dirty jets etc.
What Stian describes as dieseling is perhaps 4-stroking? Cylinder fires every other stroke due to number of reasons. One is that the mixture is just too lean to support combustion on each cycle but the unscavenged mixture left in the cylinder on the misfire stroke makes the next one rich enough to ignite. This happens normally in 2-strokes just at the light-load cruise throttle position, but also under more load where there are air leaks or lean condition caused by carb malfunction or in some cases extreme lean settings. This can cause smoke because the unburned oil is still in the exhaust when it’s ignited by the hot gas from the cylinder. Since it’s already dropped a lot in temperature it only burns partially and therefore a lot of smoke is created.
Ed, I may have too quick to dismiss carb leaning as a cause of white smoke and that’s leading you into this either / or thinking. It is pretty hard to create this situation in a motor in the absence of other problems. I usually see it in bikes with air leaks of some sort, or serious ignition malfunction like hideously incorrect timing, extremely low ignition voltage, very dirty plugs etc. Normally where the carb settings are just too lean, it’s a fairly steady state. There is a lot of heat in the exhaust and that keeps the carbon deposits at bay and you don’t see more than normal smoke. In fact you may see less. It’s when the leaks suddenly start or jets suddenly get blocked that these symptoms are the most apparent. Actually the best state for a 2-stroke is a mixture setting that’s just a little too lean. The more heat there is in the exhaust the more energy there in the gas and the better the expansion chamber works. Oil burns cleaner and keeps the exhaust unclogged. Unfortunately you are usually then just a whisker away from detonation and damage to the pistons due to excessive heat. This is one reason race motors have to be rebuilt so often…[/quote]
Gets complicated don’t it.
To go off at a tangent (or maybe an arc), you mention water charge-cooling above in the context of turbos. Would it be a reasonable option in a (normally aspirated) 2 stroke?
I’ve wondered about it, but wasn’t sure what the effect on the (marginal?) charge-lubrication might be. OTOH if the thing is tuned as above, and “a whisker away” from the dire consequences of overheating, it might be a net benefit.
I saw a DIY “bubbler” on a SR150 a few weeks ago, though the owner admitted it was just a gimmick.
i had the same problem. The smoke may be caused by the burning of excess oil. I just threw a bottle of oil in my scooter trunk and only add a swig every two weeks. That eliminated all the smoking. Just make sure to keep adding oil. If you notice that the smoking goes away after you drive it for a while, then this solution should work for you.
Filling the oil reserve or adding a little shouldn’t make difference. It supposed to get the right amount. Smoking is gone on your after a while, mine is gone also after i take it apart. Something is not right.
Sorry mods. Suggesting someone might be a social scientist definately crosses the line into personal abuse and would justify a ban (which would have the added benefit of giving everyone a rest from EdsOiler updates)
Meantime, working on my interpretation of nazmikarakoc’s interpretation of chainsmokers slightly obscure description, IF oil were to leak through the injection pump at rest, then it might collect in the inlet tract and maybe drain into the cylinder, producing a lot of smoke on startup which will gradually dissipate in use as the excess oil gets burned off.
If one habitually runs the bike with the oil reservoir almost empty, adding just enough for consumption during a journey, then the amount of excess oil available for draining at rest is limited, so the smoke will be reduced.
However, this is a high risk workaround, since if you don’t add quite enough oil and it runs out you risk seizing the engine.
A better workaround would be to run (say) something between 1:25 and 1:30 premix in the tank (these are fairly oil-rich ratios though people argue about the ideal proportions, which depend on oil quality and how hard you push the bike. With high quality oil and gentle riding one could perhaps go a bit thinner, but not much).
This should provide some diagnostic clues. If the pump is over-oiling, either by passive leakage at rest or just over-pumping, then it should smoke less on premix.
Edit: Of course you have to disconnect the pump and plug the oil inlet while on premix. I find a plastic toothpick good for plugging the RZR oil inlet. Don’t use a wooden one, they break off and its a real bugger to remove the stump.
Big if. Injection pumps are not known to pass oil when not running, at not unless completely broken and malfunctioning. 2T is also fairly viscous stuff and the top of the tank is not far above the carb, so not much head of pressure on the outlet. The nozzle into the carb is also quite small in diameter. IOW, I don’t think that is the problem here.
One thing I have seen once or twice is the seal between the oil pump and the transmission case failing so that 2T can enter the transmission and vice versa. Burning gear oil or multigrade engine oil makes a lot more smoke than 2T. Not every engine however is designed in this way, not all drive the pump from an oil-filled case.
There I fixed my original statement. I do agree it is slightly risky, but it works when you have a crappy scooter that you don’t want to smoke. You have to make sure you always have oil in there. I add about a tenth of the bottle every couple of weeks. I know this scooter so well that I can tell when it is low so i don’t even have to think about it.
Most smoking scooters seem to be on their last legs anyway.
Big if. Injection pumps are not known to pass oil when not running, at not unless completely broken and malfunctioning. 2T is also fairly viscous stuff and the top of the tank is not far above the carb, so not much head of pressure on the outlet. The nozzle into the carb is also quite small in diameter. IOW, I don’t think that is the problem here.
One thing I have seen once or twice is the seal between the oil pump and the transmission case failing so that 2T can enter the transmission and vice versa. Burning gear oil or multigrade engine oil makes a lot more smoke than 2T. Not every engine however is designed in this way, not all drive the pump from an oil-filled case.[/quote]
Only other explanation I can think of for this reported behaviour is that the oil tank empties so the pump is delivering a mixture of air and oil, effectively reducing the oiling. Maybe because of the viscosity of the oil its delivery tails off rather than cuts off sharply. If it wasn’t getting ANY oil it would presumably seize.
I can’t see how the transmission oil leakage explanation would explain the reported benefit of running the oil tank almost empty. I’d imagine transmission oil transfer would, if anything, be greater in that situation so it would smoke more.
My wife used to have a 2002 model 2 stroke scooter which had some system i can’t even understand that treats the exhaust gas like double filtering or heating and burning the exhaust gas to reduce smoke. At night you can see a red glowing core in the exhaust looking through the tail pipe and sometimes shoots small sparks.
Anyone know what that system is? It was a SYM 50cc scooter
[quote=“nazmikarakoc”]My wife used to have a 2002 model 2 stroke scooter which had some system i can’t even understand that treats the exhaust gas like double filtering or heating and burning the exhaust gas to reduce smoke. At night you can see a red glowing core in the exhaust looking through the tail pipe and sometimes shoots small sparks.
Anyone know what that system is? It was a SYM 50cc scooter[/quote]
Dunno about that specifically, but Sulavaca has talked about an exhaust “catalyst” that seems to be a wire mesh that gets red hot and helps burn off exhaust hydrocarbons. I THINK this was on a ＳYM Wolf but maybe 2-strokes also have them. I dunno if the wire is anything fancy with a real catalytic effect but I’d guess not.
You’d think that to work it’d need additional air introduced into the exhaust gasses (which’ll be a bit short of free oxygen) but I dunno if they do that.
I told them to try hooking up a new CDI to see if that improves anything. A local mechanic told me that if it were the CDI or ignition coil then the scooter would be noticeably rough to ride (which mine isn’t). He said it would be carb.
They’ll phone me back after they’ve tried it with a new CDI.
Anyone know how to say ignition coil in Chinese? Or failing that a picture of one I can show them?
This has become a personal mission now to get the scooter as near smoke free as possible.
I hate it when they keep telling me “it’s normal it’s a 2 stroke” because I’ve owned a dozen other 2 strokes and when they are warmed up they produced no visible smoke. My 50cc Dio which I presently own doesn’t even make smoke on a cold start and I’ve been riding it for years.
Got the scooter back. It still visibly smokes. But it’s 1/10th of what it used to be. But that’s still ten times more than my Dio. Oh well. Better than nothing.
I LOVED my Dio. Bought it 2nd hand for NT6000 and rode from Kuting to Taishan and back for years. Hardly ever smoked, but then when I moved to the mountains she couldn’t handle it.