High idle and loads of white smoke

[jcalcutt]

Hi,

I was riding home yesterday (on Vespa PX 125), everything was fine until suddenly I noticed when I released the trottle it wouldn't go back down to a normal idle. I got home and let it sit and the engine was idleing as if I had the throttle open slightly. Then i noticed white smoke starting to come out the exaust. If I start the bike now it blows out loads of white smoke and the idle is crazy. I've cleaned the carb and jets, made no difference. I'm thinking maybe an air leak somewhere, broken gasket. The gear oil is dirty but doesn't really smell like petrol. I'm out of ideas really on where to look next. Has anybody got any advice?

Thanks,

Jon

[henri]

first guess ,blown clutch side seal, H

[jcalcutt]

I'm guessing that's not an easy fix then?

[henri]

nope sorry its not , so its worth going thru some over checks first , remove the gearbox breather an plug hole with ya finger or a bolt , if that reduces ya idle its proof the seals shot , often but not always gear oil will smell of petrol as proof aswell . H

[jcalcutt]

Ok thanks. I'll try that. Is the gearbox breather easy to get to?

[henri]

not impossible ,but nothings easy to get too on a vespa , its high on the engine up inside the wheelarch ,easiest way is to block up the scoot an remove rear wheel . H

[jcalcutt]

Ok, thanks. I'll let you know how it goes.

[vespasco]

My first instincts are also that the clutch seal is the cause.

But do also check /re torque your carb and head

[henri]

as vespaco says , check easy stuff first , i'm a "sheditte" by nature ,so any excuse to drop a engine n reduce to component parts means more happy hours in shed for me , but its a lot of hours work just to find a few minutes checkin torques would see ya still riding .
but it being fine ,then suddenly not says to me somethings given up the ghost , clutch side seal being main suspect ,i'm not a betting man but thats were my money would be put , H

[sbwnik]

Again, crank main/clutch side seal. An easier version of the oil breather test is to take the airfilter off the carb and slowly cut the airflow back with your thumb. It should start to struggle to tick over, but if you can get over 3/4 covered without it changing much, then I'd be almost certain of a blown seal. If it dies before half covered, then it's not likely to be on that side of it.

Thick white smoke though.... Not promising.