banshee compression off

[sangheraent]

well i built a motor last year 4 mill agressive trail port with 21cc domes. I am tearing it apart to change a crank seal and i noticed one cylinder has 150psi and the other has 100psi compression. The motor doesnt even have 20 hours on it. it was leaking coolant and motor oil and one cylinder got messed up. Can i hone and change the rings to get compression back up or do i need to go new top end? pistons looks like new and the bore has no scratches at all.

[SAVAGE420]

Was a ring stuck at all did you notice?

[sangheraent]

no but there was water in both cylinders mixed with motor oil. and the o rings on the head were all buggerd up. I guess I should have done a leakdown test when I built the motor. damn cool head is so hard to install with the damn o rings always falling out of place.

[Cali]

no but there was water in both cylinders mixed with motor oil. and the o rings on the head were all buggerd up. I guess I should have done a leakdown test when I built the motor. damn cool head is so hard to install with the damn o rings always falling out of place.

When I put my cool head on, I had the same problem with the orings.I took some light greese and lightly put it inside the groves b4, puting the orings on.It held my orings long enough to put together.I got about 3 hours on my top end with no problems.Nid pressure test after engine was built and no leaks.

[SAVAGE420]

Yeah, leak down should have been a MUST.

 

I always just use some bearing grease and put in in my fingers and then grab all the o-rings as i go and coat them really well. They stay in place like nobody's business while putting the head on.

[sangheraent]

i used grease too but the head is such a close fit that it jerks a little when it gets caught. oh well but can i do anything about the 1 piston with low comp or am i in for a new top end?

[firebanshee]

I would just re ring it and hone it like you said,if everything looks new you should be good to go. Your compression loss was the bad oring, you might not even need new rings if you are on a budget.If you put it back together and don't like the compression then you have lost nothing but a little labor cause the coolhead o rings are reusable if they still look good just use good grease.