looking for advice on G9 just started smoking

[cinejeff]

I am working on yet another friends G9 and could use some advice.

It runs but it started smoking something fierce. Wondering it is is time for a rebuild or maybe get lucky and something simple like pcv valve or head gasket.

The compression is 165psi. Valves set OK at .004 thousand, carb cleaned out, pvc cleaned out, changed oil with 1 qt. Oil was correct level but old oil seemed a little dark brown, milky and a little thin/gassy, but only slightly. No oil in air box or filter. I ran it for about 15 mins with new oil, still smokes about the same.

The cart runs good without airbox, but have to choke it about 50% with airbox on to get it to run as good. Smokes either way.

Do the head gaskets go on these? Is there a measurement I can take, or something that would indicate visually that its the rings with the head off before I pull the engine?


Just wondering where I should focus my energy next.

[marks141]

Pull the muffler off and see if it continues to smoke, sometime oil can get in there. If it still smokes you may need some new rings and seals


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[cgtech]

Or could be a over full oil condition, usually caused by a bad needle in the carb. I suggest changing the oil & refilling with one QT only, no more. And check inside the airbox for oil.

[marks141]

Looks like he did that already and all was good


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[sho305]

I only know the oil ring goes first and they start to smoke, this usually does not happen all at once. I guess it might but not in carts I have seen. Not sure what else would cause oil smoke other than oil in the airbox.

[cinejeff]

Here is a quick update. I pulled out the engine last night and pulled the head. I could see a little pool of oil sitting on top of the rings on the low end. The piston is stamped oversized .25mm but has about 2mm of gap side to side. I can "flop" the piston front and back about 1.5-2mm so I guess it is time for a rebore and new piston/rings. Does anyone know what the max oversized is for a G9 engine??? .5, .75, 1.00 ???