Kymco agility city 50 my exhaust is smoking

[agilitycity50]

Hi I have cut the cdi box and replaced my original jet with a #86 and I can hit 40mph but after a good ride my exhaust started to smoke in the middle of it, could it just be a hole in my exhaust pipe or is something going wrong?

[baddi]

Usually, when the exhaust of a four-stroke is visible it is because the mixture is not fully burned when it leaves the cylinder and it can be caused by a couple of things:

- Leaking valves.
- Motor oil being able to enter the combustion chamber.
- Too cool spark plug (being sooted).
- Waaaaaaay too rich mixture.

If the spark plug is the same as before and is sooted, you may have to use a slightly smaller main jet. Don't be afraid of overheating the engine, i have run waaay lean mixtures and waaay rich mixtures and all in between and the highest engine temp (measured at a valve cover bolt) has been 88 degrees celcius on a very hot summer day, but it wont normally hit 80 for me. :p

You should also check if there are oil in the intake, because then the rubber seal thingy on the valves may be leaking. I do not know the english word for this piece, as it in danish is called an "oil thief". The thingy is this one: http://scootergrisen.dk/scooterhjemmeside/billeder/billed3047.jpg

You can check if the valves are leaking in several ways. The best way is to get the proper measuring tools that can identify how much it is leaking, but at the intake valve you can turn the engine to exhaust stroke and put a little fuel in the intake so it covers the valve and then by hand turn the engine backwards. If you see bubbles, the valve is leaking, but this method can only be used on the intake valve, since it is pointing upwards.
You can also lick a finger and shove it up the intake or exhaust until you can feel the valve and then turn the engine by hand. If you feel any sucktion or pressure when the valves are closed, they are leaking, but this is not very objective as it relies on your feeling.

But first things first: check the colour of the spark plug and change main jet if needed. It may just be that you need an #85 or #84.

[agilitycity50]

thanx 4 posting and also when the bike is on the stand the wheel will spin very very fast and create smoke

[reg]

Hi, if you have cut the cdi derestriction wire then your engine will now rev much higher than before. It is essential when derestricting the cdi to replace the variator collar with a smooth derestricted one. It sounds like your engine is burning oil because its revving around 12,000 rpm.

[agilitycity50]

yeah I thick that's the case does any1 know where to get them cheap?

[baddi]

Hi, if you have cut the cdi derestriction wire then your engine will now rev much higher than before. It is essential when derestricting the cdi to replace the variator collar with a smooth derestricted one. It sounds like your engine is burning oil because its revving around 12,000 rpm.

Now, i am not very much aware of the differences of the agility and agility city motorwise, but on the normal agility, the engine will only be able to rev up to 9000 rpm after the CDI has been cut. Is the City model totally unrestricted after the CDI has been cut?

Also, i have revved the engine up to 12.000 a couple of times to taunt it a little and never has it smelled like it was burning oil and never has it been smoking. The only thing that has been able to make it smoke for me was a mixture over twice as rich as needed (AFR 6).

[woodcutter]

yes, de-restricted agility 50 is reving at 9.000rpm max

don't know about city 50, but it should be the same?

how old is it and how many miles/kms you have on your scooter agilitycity50?

de-restriction on it should be:

1. smooth drive boss
2. bigger jet, I think it's 86
3. removal of small plastic part inside airbox
4. cdi wire cut

Maybe it's running too rich causing high oil level (unburned fuel is mixed with oil and creating high oil pressure and forced back into combustion chamber) making it smoking?

[baddi]

Woodcutter just gave me an idea of what could be the problem.
Oil should not be forced up by the piston rings in any significant amount, but there are som blow-by gasses that always passes by the piston rings. To prevent the crankcase pressure from rising too high and blowing out gasghets, there is a tube from the valve cover to the air filter where this blow-by gasses are sucked back into the air stream and ignited but to get rid of all the oil droplets that might be sucked up aswell there is a condention tube where oil and water vapour condenses and this should be emptied once in a while to minimize the amount of oil getting into the air stream.

Perhaps your tube is full and needs to be emptied?

[reg]

Hi, the smooth variator bosses are on ebay.

extra 7mph straight away and easier on the engine.