Sorry for the repost- no reponse last time and I can't believe there isn't soneone out there who knows this.
I'm looking for advice. My son has a blaster. He rides it and I get to fix it. Problem is, I don't know anything about 2 strokes although between us we're learning. Last time it broke down we replaced the piston and had the cylinder rebored to fit. We put in a new plug and it ran great....but only for 1 day. The next day it wouldn't start at all. It sounded like it was going to but it just wouldn't. We took the top end off to check and it looked OK except for oil on the plug - not 2 stroke oil. We put it back together and put in another new plug and it works ok again but I'm worried about the oil getting into the cylinder and fouling the plug again. Someone told me that it could be a cracked crankcase (sounds serious) or a leaky crankshaft seal causing transmission oil to get in. A crankcase seal sounds like something I could handle but I've no idea where this is or how to check it and replace it. I don't want to go to a dealer because we got ripped off pretty bad last time we did that. Does anyone know where I can get more info on this problem or details on how to check and replace the seal. Any help would be appreciated.

 

What makes you so sure that it's not 2cycle oil on the plug? After trying to start it for a while it would certainly have some 2 cycle oil on it. Is the machine losing transmission fluid when it is running?

 

Well, it doesn't smell like 2 stroke oil and it doesn't taste like 2 stroke oil. I don't know if its losing transmission fluid because he stopped riding it after we found this problem - we didn't want to damage the piston again. It starts up first time - no problem - but the plug is drenched in oil after just a few seconds of running. I've taken off the top end again and when I rotate the crankshaft I can see oil on the underside. I've looked into how to replace the oil seals and I really don't want to remove the engine and crack the case.

 

Have you done a compression check and is it in specs?
If the crank seals are shot, the compression will be low, and the compression wont come up, by oiling the cylinder. Usually the compression is checked, and if its low, add a few drops of 2 stoke oil down the spark plug hole (this will help seal the rings, if they are the problem), but if adding the oil doesnt help the compression...the crank seals are most likely the problem.
Some times, just using the motor, will help the seals to come back.
This just started acting up, after the piston change? it didnt have this issue before?

 

I haven't checked the compression - how do you do that?
It was running fine before til my son added some stp octane booster to the fuel - don't ask me why. That must have overheated things in the cylinder and the piston rings and piston were badly damaged.

 

Compression checkers, are pretty simple, and they replace the spark plug, and after spinning the motor over, they show how much compression a motor has. Before going any further, check that.
Basicly you either thread the gauge or hose into the spark plug hole, hold the throttle wide open, and kick over the motor...3 times or so. Then read the gauge...im not sure what the minimum specs for that motor...but if it has 90 psi or better, it should start.