Excessive 2-Stroke Smoke

Thanks Sula. I get so tired of rebutting the guff posted about ‘evil’ 2-strokes again and again, endlessly, ad infinitum, ad nauseum.

[quote=“Mordeth”]

They gave me a new piston and cylinder. It’s still smoking.[/quote]

Things that cause smoke in order:

1- Clogged muffler. (only smokes when hot)

2- Piston rings. (smokes all the time)

3- Faulty or poorly adjusted throttle/oil pump cable. (smokes all the time)

4- Faulty ignition. (smokes all the time)

5- Carb issues… (Can cause smoke but not common)

6- Moisture in gas tank. (causes white smoke. Not blue smoke.)

1 and 2 you already fixed. I would look at changing the throttle cable(3), or at least making sure that the cable allows for the oil pump lever to rest on its rightful position when you turn the throttle. A good way to tell if it’s adjusted and working right… Is to make sure the pump lever has full range when you turn the throttle. The oil pump cable should lose tension slightly on idle position. If that doesn’t help, I’d be looking at the ignition coil and CDI. And finally, I would consider changing the carb if all else fails. If 1 to 5 above are done in the same order, the bike will no longer smoke when it’s warm. Slight smoke on cold starts is normal.

Did the mechanic get a new sleeve for you or did he just do a maintenance bore? When they bore the sleeve, they often adjust the oil pump/throttle cable to pump more oil to compensate for possible tight fits by the machinists as to avoid you seizing the engine you just paid for them to rebuild. 99% of mechanics will not install a new sleeve, by the way. They just have it machined and they install a new piston, piston rings and crank shaft bearing. My guess is that they messed up the oil pump/throttle cable adjustment to make sure you don’t seize the new piston (3). I suggest you go to a different mechanic and request them to install a new throttle cable… If it still smokes after that… Chances are you have an electrical problem (4).

No problem. I understand many have automatic feelings towards certain types of technology. The whole ‘save the environment’ thing has caused a lot of people, including many journalists and even government policy makers to make so many senseless knee jerk conclusions and reactions that I can’t blame anyone for not seeing the whole picture to be honest.

I tried to make a fuller post so that even my lazy self can link back to it in future, or just cut and paste.

Moredeth, I haven’t read all the posts, but is there enough oil being drawn in? Starvation could also be causing your smoke.

[quote=“Doorman”]
Things that cause smoke in order:

1- Clogged muffler. (only smokes when hot)

2- Piston rings. (smokes all the time)

3- Faulty or poorly adjusted throttle/oil pump cable. (smokes all the time)

4- Faulty ignition. (smokes all the time)

5- Carb issues… (Can cause smoke but not common)

6- Moisture in gas tank. (causes white smoke. Not blue smoke.)[/quote]

No.

  1. Piston rings. Bad rings in a 2-stroke do not cause smoke, just loss of compression and performance. The rings do not do oil control duty. There are only two rings in a street motor and they are both for compression only.

  2. Water in the gas does not cause visible smoke. If the water can be carried in the fuel (it’s insoluble in regular gasoline) it makes water vapor which in a warm engine is invisible.

You forgot oil control via the crankshaft seals. It’s very, very common for the seals between the crankcase and transmission case to wear and allow transmission oil to be drawn in, causing white smoke. Very common.

[quote=“redwagon”]

You forgot oil control via the crankshaft seals. It’s very, very common for the seals between the crankcase and transmission case to wear and allow transmission oil to be drawn in, causing white smoke. Very common.[/quote]On a two strokes 50cc? Impossible. The transmission oil on a 50cc has no way to even go near the combustion chamber.

A lot of moisture in the gas tank will cause white smoke and hard starts. I don’t agree with you.

This dude begs to differ. :wink:

kymco.com.tw/products/models … index.html

Check out the quadruple rear shocks on that baby!

Incubus, the “no 2-smokes” ban is on new sales. Existing 2-smokes are grandfathered.

Mordeth, if I were you, I’d sell it and get a mo’ bettah scoot.

The only other “conditions” the scooter has is that it regularly (every year) has the electric starter fail. Seems like each year for one reason or another it won’t start with the electric starter. So does that point to the CDI?

Mr Sulavaca’s plea for thought rather than knee-jerk reaction is well made, though that won’t play well with punters or politicians.

In detail, there are a couple of dodgy bits.

Not sure I would. I can’t see why CO or CO2 would necessarily be much worse, except pehaps because efficiency might be a bit lower . Havn’t seen any numbers, but I think the main difference is going to be HC, which is likely to be massively greater with a “traditional” 2-stroke

This is a questionable basis for comparison (though that’s perhaps your general point anyway)…

A “single engine revolution cycle” is a bit unclear, but I take it to mean one 4-stroke cycle, so its a scooter cylinder to car cylinder comparison. Scooters will probably emit more on this basis, since they dont have the EFI, water cooling and catalytic cleanup that most cars have.

However, they have fewer, smaller cylinders and are smaller and lighter, their total emissions are much less both in use and in production, and this should NOT [quote]“at least cause a four stroke scooter user to question their own moral standing when it comes to typical pollution running cost production.”[/quote]

Picky, I know. Knee-jerks are so much easier.

This dude begs to differ. :wink:

kymco.com.tw/products/models … index.html

Check out the quadruple rear shocks on that baby![/quote]

FFS! That King Thing, which is clearly being sold as a “utility” bike, appears to have a fuckwitted, sportbike stylee exposed chain. Moronic Mototorcyle Marketting Madness

[quote=“Doorman”][quote=“redwagon”]On a two strokes 50cc? Impossible. The transmission oil on a 50cc has no way to even go near the combustion chamber.

A lot of moisture in the gas tank will cause white smoke and hard starts. I don’t agree with you.[/quote][/quote]
Yes, a scooter in specific with a CVT transmission has no fluids in the case to pass into the crankcase. It sounded like you were talking about 2-strokes in general, rather than Mordeth’s scooter in particular.

Define ‘a lot of moisture’. Water does not dissolve in straight gasoline. Therefore a large amount of moisture causes the engine not to run at all, therefore no smoke at all. E85 or other ‘gasohol’ type fuels can absorb a fair amount of water and allow the engine to burn it, but I don’t think that is what you are getting at. Remember that a lot of turbo 4-stroke applications use water injection to lower charge temperatures and do not produce visible smoke, even when quite high volumes of water are added to the intake charge.
Are you perhaps thinking of the practice of attempting to clean combustion chamber deposits by adding water to a running engine by squirting it straight into the intake? Sure that produces visible water vapor but the fuel system itself could not deliver that amount of water to a running engine simply because water in the tank sinks to the bottom where the feed is and then the fuel lines get only water… and the engine won’t run at all on straight water.

This dude begs to differ. :wink:

kymco.com.tw/products/models … index.html

Check out the quadruple rear shocks on that baby![/quote]

I’m not sure that vehicle has been put into gas bottle delivering practice though. It would ultimately depend on the useful torque produced by that engine and transmission. Two strokes have so far been greatly appreciated more than four strokes because of their greater power output per cc.

[quote=“California EPA 2003”]The U.S. Environmental Protection Agency (EPA) is adopting more
stringent emission standards for new highway motorcycles. Under the
current standards, which are over 20 years old, today’s motorcycles
produce more harmful emissions per mile than a car or even a large
sport utility vehicle (SUV). These new standards will reduce the
combined hydrocarbon and nitrogen oxide emissions in the exhaust by
50 percent as well as the harmful health effects of mobile source air
toxics.
[/quote]

[quote=“California EPA 2003”]Are motorcycles a less-polluting alternative to cars
and SUVs?
In fact, motorcycles produce more harmful emissions per mile than a car,
or even a large SUV. The current federal motorcycle standard for hydro-
carbon emissions is about 90 times the hydrocarbon standard for today’s
passenger cars. Although many of today’s motorcycles will actually meet
the current California standards, the California hydrocarbon standard is
still 18 to 24 times the current federal passenger car limit, depending on
the displacement of the motorcycle engine.
[/quote]

The fact is that the smaller the engine, the less efficient it tends to be. This is an irony really as the friction within a smaller engine is greater per HP expelled, reducing efficiency. This is also one of the reasons that recent car engines have been growing larger to reduce frictional forces, whilst adopting other technologies such as stratified injection, CVC gearboxes, Atkinson cycles, fly by wire etc. The larger car engine phenomenon is another one of those knee jerk reaction causers used by even environmentalists in their dirty car manufacturer campaigns. They often prefer to show how engines are increasing in size, just to show how nasty the bad ass car companies must be.

There is no simple answer to which kind of transport is the least polluting edithglow. You are correct in assuming that is what I am getting at. In regards to CO production in two strokes. It is certainly higher as by the very nature of the typical petrol two stroke motor scooter engine, its very design flaw is that it partially burns its fuel-oil mixture, rather than makes a closer to complete burn as in a four stroke cycle. This will generally be noted in both fuel efficiency for one, and total oil consumption. As these vehicles neither generally have substantial catalysts to scrub the HC, CO and CO2 from the exhaust, then much of that generally comes straight out the back.

[quote="redwagon… and the engine won’t run at all on straight water.[/quote]

Damn! You mean I wasted my money?

But seriously though, if there’s no oil in the CVT, could an air leak via the crankshaft lean the mixture to the point where it doesn’t burn properly, producing smoke, or would it just not run at all in that situation?

[quote=“Ducked”]
But seriously though, if there’s no oil in the CVT, could an air leak via the crankshaft lean the mixture to the point where it doesn’t burn properly, producing smoke, or would it just not run at all in that situation?[/quote]
If it’s lean enough to produce visible white smoke, then no, they typically won’t run reliably in that state. Lots of stalling and refusal to run under a few thousand rpm, detonation etc. You’d have to be pretty determined to kill the motor to keep trying to run it in that state.

Mordeth’s problem is more likely incorrect oil pump setting, poor 2T oil quality, air leak, incorrect mixture, incorrect ignition timing or failing ignition system. As Doorman noted, a clogged exhaust will make smoke if someone suddenly starts riding the machine harder than it’s used to, because the built-up carbon in the muffler starts burning off. Perhaps if Mordeth started riding his wife’s scooter the way he rides his Ninja, this could be the issue.

Are the cops still on the lookout for you Mordeth? You riding a scooter now to hide your identity? :wink:

[quote]Are you perhaps thinking of the practice of attempting to clean combustion chamber deposits by adding water to a running engine by squirting it straight into the intake?[/quote]Yes. [quote]Sure that produces visible water vapor but the fuel system itself could not deliver that amount of water to a running engine simply because water in the tank sinks to the bottom where the feed is and then the fuel lines get only water… and the engine won’t run at all on straight water.[/quote]But wouldn’t that be enough to cause poor ignition and smoke?

[quote]Mordeth’s problem is more likely incorrect oil pump setting, poor 2T oil quality, air leak, incorrect mixture, incorrect ignition timing or failing ignition system.[/quote]These are high on the lists of suspects.

[quote] a clogged exhaust will make smoke if someone suddenly starts riding the machine harder than it’s used to, because the built-up carbon in the muffler starts burning off. Perhaps if Mordeth started riding his wife’s scooter the way he rides his Ninja, this could be the issue.[/quote]I think he mentioned replacing the muffler already.

[quote]I’m not sure that vehicle has been put into gas bottle delivering practice though.[/quote]I haven’t seen one yet. I’ve seen the odd older Kymco models rigged for gas delivery but not the new ones with quadruple rear shocks. Looks like that’s what they are marketing them for.

It’s a very small window of possibility. Once you get enough water in the gas to cause that level of misfiring you have so much in the carb’s float chamber that any throttle application pulls only water into the main jet and the engine dies. You roll off the throttle and it catches again. This is the opposite of the attempts to clean carbon out, where you rev the motor hard and then squirt water in until it almost dies, let it recover, repeat.

Again, you don’t get ‘moisture’ in the gas tank. It condenses out into liquid water and that sinks to the bottom of the fuel tank. When it gets high enough to make it into the filter tube on the tap, it quickly fills the carb float chamber from the bottom up, until it reaches the jets. Then the vacuum pulls that up instead of the gas… the two don’t get mixed up. Simply draining the float chamber with the drain screw will get rid of the water and the motor will then run correctly until the process repeats itself.

BTW, half a liter of methanol in the tank will absorb all the water in there and allow it to mix and then burn cleanly with the gas. Given Taiwan’s high humidity it’s not a bad idea to do this once a year.

[quote=“redwagon”][quote=“Ducked”]
But seriously though, if there’s no oil in the CVT, could an air leak via the crankshaft lean the mixture to the point where it doesn’t burn properly, producing smoke, or would it just not run at all in that situation?[/quote]
If it’s lean enough to produce visible white smoke, then no, they typically won’t run reliably in that state. Lots of stalling and refusal to run under a few thousand rpm, detonation etc. You’d have to be pretty determined to kill the motor to keep trying to run it in that state.

Mordeth’s problem is more likely incorrect oil pump setting, poor 2T oil quality, air leak, incorrect mixture, incorrect ignition timing or failing ignition system. :[/quote]

OK, if an air leak won’t produce smoke by leaning, er…how does it produce smoke?

I’ve seen a bike with double rear shocks, THINK it was a Wolf but I’m not sure now, maybe it was a King. I assumed it was a one-off mod and I asked the (English speaking) laoban of the breakfast store it had pulled up at why. He said the customer had a rather large girlfriend. :neutral:

Misfiring, incomplete combustion, abnormally high exhaust temperatures burning off carbon in the exhaust.

Out scooter produce white smoke when dieseling.
Happen from time to time when hot and running at low load and not quite high top speed.
Guess it’s running lean or when it’s running 50-60 and the trotle is not fully open.

[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.