why is my engine blown

[Zman]

I am sure you know if the spark plug is always wet you have a problem. You are either getting way too much fuel or you are not getting spark or enough spark with the plug in the engine. Maybe you are getting a poor spark. Try to shorten the spark plug gap to something very small like 0.3mm.

Silly question, did you put a rag stuck in the airbox when you had it apart?

Did you replace the crank seals when you rebuilt the engine. The old seals go bad and give you a bad air leak which will cause you to go lean.

[Zman]

A short plug gap is for test purposes not to fix the problem.

[grachal]

Thanks guys!

@Biff: The waterpump impeller was fine. I replaced the impeller, the drive gear and all the seals last year, and they are still good.

@Zman: Crank seals, of course are new, genuine viton ones. No rag in the airbox, so it should get sufficient air. Spark outside the engine is very nice and bright, inside might be a different story tho. I will try reducing the gap. I also will check the carburetor, it sat for a few months, maybe the float doesn't close. But it doens't leak out the vents so I didn't bother looking at the carb

[Jacob 'Berg]

Pull the crank case drain bolt and make sure you do not have any coolant in the crank case.

I had a similar experience after a rebuild and had a small leak at the coolant passage between the case halves.

[gasser]

If you had not said that you checked the timing I would suspect that the woodruff key sheared on the ignition side of the crank when your motor locked up. You might want to check your timing again.

[grachal]

@Jacobs 'Berg: Ok, so today I removed the crankcase drain bolt, but no coolant came out, just fuel.
I also removed the carb a few times, but did not find anything. The jets are clear, no debris or oil residue. The float valve works fine.
I also tried cranking it without the drain bolt, and it sputters out loads of fuel.
@gasser: Thank you. When I rebuilt the engine I of course had to remove the flywheel, and the key was fine. But maybe something went wrong assembling it. I will remove the flywheel again, and check if the key is there.

[SS109]

If a lot of fuel is coming out of the crankcase (not trans) bolt then the float in the carb isn't working properly.

[Jacob 'Berg]

Originally Posted by grachal

@Jacobs 'Berg: Ok, so today I removed the crankcase drain bolt, but no coolant came out, just fuel.
I also removed the carb a few times, but did not find anything. The jets are clear, no debris or oil residue. The float valve works fine.
I also tried cranking it without the drain bolt, and it sputters out loads of fuel.
@gasser: Thank you. When I rebuilt the engine I of course had to remove the flywheel, and the key was fine. But maybe something went wrong assembling it. I will remove the flywheel again, and check if the key is there.

Don't turn over the motor with the crank case drain bolt out, you will be pulling unfiltered air right into the crank case!

If you are getting proper air and fuel mixture, you are not getting a good spark, or do not have good compression. Or, as stated above the timing is off.

[grachal]

Thank you so much guys, finally she is up and running again! The carburetor was the issue. Even tho I tested the float by blowing into the fuel line and actuating it, it seemed to get stuck once there was fuel in the carb. Had it all apart again, and put it in a ultrasonic cleaner.
She pulls stronger than ever before and the idle is smooth like it was an injection system. Only thing that concerns me, is the quite noticeable powervalve rattle. But I will get it sorted out.
gassn.jpg

[grachal]

Short update:
just after 53 kilometers I managed to seize her again. The motor started to develop a high pitch squealing noise, but ran great so I tried to bring her home unter its own power. 200 meters further, engine shut off with no compression.

Now it starts back up, but doesnt sound all that great. I hope that the crank is fine. Maybe I get away with yet another new piston.