Compression Jump

[werner]

Just replaced the orings on my Noss Head. Background: Did pistons and rings last year this time and compression test with my 19cc domes at sealevel read 183psi just as it should be with minimal riding since then. Had some trouble with sparkplug leaking oily residue out top of head so i decided to replace head orings and plugs as precaution.

 

Just took head off and installed new oring kit, replaced head, did a compression test. All of the sudden my comp test showed 210 psi each cylinder. Did test 3 times each cylinder, WOT and not, regardless read the same.

 

Im going to try the comp tester on another bike to ensure tester is not bad but just curious if anybody knows why this might have happened or had this happen to them before.

[wesw]

sounds liek what ever you did sealed something up really tight. compared to earlier. probably why you were leaking oil or whatever.

 

have you checked the squish on both sides. might be a bit tight.

 

210 is alot of compression, alky compression imo.

 

if your gauge reads correctly.

[badassbanshee479]

I would get another gauge and try that first.

19cc dome at sea level should be around 183 psi. did you put a small base gasket in when you did the top end??

like wes said, check your squish

[dajogejr]

210 is too high for alky IMO, of course squish, bore % to squish band %, timing as well as a few other factors would chime in there as well.

 

I would test with another gauge, as said...and check the squish. Something ain't right....

[werner]

whats the best way to test squish.

 

used a different tester, took head back off and reinstalled to make sure there wasnt something done wrong. still reads 210. i cant figure out whats going on. there is no way to increase compression unless domes are changed....cant think of anything with the crank or rods to make it stroke higher

 

nobody has seen this before?

[shee rips]

you check for squish with a peice of solder. bend it 90 degrees and put it through the spark plug hole . make sure it goes all the way to the side of the cylinder. then turn the motor over with the kickstarter so the piston squishes the solder. then pull it out and measure it. that is your squish.

it is strange the way the compression jumped that much. is it possible that they are smaller domes or something. :shrug: