smokey on startup....WHY?

[pitmaster]

Mates wants to know, why his Lifan 140 is smokey on startup?

it last for about 30 seconds, its white/grey smoke, its not steam etc cause it hangs around like smoke, and doesnt fade quickly like steam,

motor has done less than 15 hours, about 2 weeks ago he pulled done the top end to check for a tap he had, turned out to be the timing chain wheel,

but the past week its now smokey on startup,

rings were rotated 180 when installed, ring gaps checked (.02) piston - bore clearance checked, bore still had original hone marks,

any thoughts?

 

[Sidney]

I'm sure it's nothing it could just be some moisture in the engine.

 

[pitmaster]

moisture would create steam, which dissipates quickly.

this hangs around like smoke does, and makes you cough,

 

[Sidney]

Nah it can still be mouisture. The other day when I washed my bike with the hose it made white smoke for a min and the motor was cold so it wouldn't have evapourated straight away.

 

[Benjo]

if its not that old maybe change the oil the bike came with if u havent changed it already the oil it comes with if crap

 

[luke#92]

i think u should clean out the Carburetor

 

[hoss2k4]

If he removed the cylinder and didn't re-ring the piston, the rings may not be sealing very well and could easily be the problem.

 

[pitmaster]

If he removed the cylinder and didn't re-ring the piston, the rings may not be sealing very well and could easily be the problem.

so he should have put new rings on? even though they were only few hours old! is there anyway of getting these rings to seal?

Thanks

 

[Fattmungus]

generally if a motor is smokey on startup , with the smoke clearing after a while, it is a valve guide/seal problem. when the motor is off, oil leaks down the guide and sits in the chamber. when u start it, it gets burnt (hence smoke). the exhaust seal isnt too critical, but the inlet guide/seal is cause when the inlet valve opens, the piston is on the intake stroke therefore drawing in air and fuel and also trying to suck the oil down the guide. on the exhaust stroke the air is gettin forced out therefore not tring to suck oil down the guide. probly the opposite in fact. it would be advisable to put a bit of a hone pattern on the bore if u took the rings out. either get a machine shop to do it or if you are pushed for cash, rough up the bore in a cross hatch pattern lightly with some fine sandpaper. like 400 or maybe 800 wet and dry. also u said ring gaps were .02? if u mean millimetres then that is less than one thou in which case, wouldnt be good. i believe it is 3 to 4 thou per inch of bore size +1. so for example if it is a 2 inch bore then 4 x 2 + 1 = 9. the reason i said 4 is i would rather lack a little bit of compression than seize the motor. hope this helps

 

[Ryzzy]

make sure ya breather isnt blocked, cos if it is it causes pressure to build up in the case which can pop seals out of their seats and push oil up and into places it shouldnt be (like into the bore)
i had this happen on a few bikes that came into work

 

[darb110]

mate your bikes just cold... every bike has abit of a smoke when there started up.. warm her up and as you said its fine =) if you were pinging through the bush and it was blowing smoke then id be worried

 

[hoss2k4]

mate your bikes just cold... every bike has abit of a smoke when there started up.. warm her up and as you said its fine =) if you were pinging through the bush and it was blowing smoke then id be worried

Sorry but I disagree. None of my bikes smoke on start up.

 

[crazzy #1]

make sure ya breather isnt blocked, cos if it is it causes pressure to build up in the case which can pop seals out of their seats and push oil up and into places it shouldnt be (like into the bore)
i had this happen on a few bikes that came into work

^^^^^^^^^^^

 

[Cactus Jack]

Fattmungus is spot on - that's everything I would have said ! Ring seal is broken once you remove the piston from the cylinder plus the rings can be stretched out of round if removed from the piston ! The seal loss is microscopic but enough to cause a puff of smoke when you back off and throttle back on ! I've seen valve stem seal oil leaks first hand in brand new and used heads - even after they've been taken OFF the engine ! The carbon in the combustion chamber and the valve heads and seats become oily just sitting on the shelf even though everything was perfectly dry when first removed and it can only be travelling down the valve stems !

A puff off smoke on start up that goes away is definitely a seal leak ! Also - did your mate put the oil gallery seal back in properly ? Oil can get past a used head gasket when the engine is cold then seal up as it warms up ! If it's the rings - they'll eventually reseal again with use !