appiston damage

[lilpain]

so i did a copression test on my 98 gti pto side 7 psi the other on 122 psi ,took top end off and top of pistons are damege is missing a big shunk of the pistin ring,cylinder wall look good no scratches.top of cylinder head is also chip any help will be appreciate.

 

[seadoosnipe]

Depending on your level of experience, you may be able to find the root cause of why you dropped the PTO piston, then decide if you only want to do the top end, which is a bit cheaper than a total motor replacement. In my experience, a large percentage of the time, you'll find it more cost efficient in doing the total engine. In the long run, it saves you time, and for a few hundred bucks more, you will have the complete engine.

This cylinder could have dropped for many different reasons. Whether is was an oil injector line break or stop up, the carb run lean, problem in the cooling system or just detonation, the root cause really needs to be found. If you lost that cylinder due to your carb, buy a new motor and put the carb(s) back on, it could happen all over again. So, try to find out as much as you can to the problem.

If the motor took a lot of wear from playing around in the water, it's possible it's a crank bearing, in which case, the new motor will be all you need to replace.

Good luck!!!

 

[lilpain]

It is apart bearing are good no play .the pistons have lil holes on top.

 

[seadoosnipe]

That sounds like detonation. Post some pictures if you can. Detonation is caused from the ignition happening outside of the normal sequence, firing off side instead of directly under the spark plug. It happens for different reasons; problems with the cooling system, carbs not adjusted right (leaned out, causing too much heat, etc...), or even air leaks. Once it starts, it can actually heat up the cylinder to the point, the spark plug and cylinder begin to melt. It can continue to run even after you shut off the engine. There is several faucets to the extent at which this takes place.

If you go with just the upper end rebuild, make sure all of your calibrated fittings in your cooling system are clear, and your carb(s) are set up correctly.