Compression

[sammyfranziska]

Hi im in the process of rebuilding the engine on my 86 and have ran into an issue trying to get compression. I rebuilt the head and by every measure in the manuals i have it correct and the timing correct on the bike yet im only getting 40-60 lbs compression on each cylinder i did a leak down test and it passed at 90lbs ao im scratching my head as to what could be wrong any advice would be great

[Nails]

It's difficult to get a good compression reading on these bikes. That's the best I can offer from what you said.

[sammyfranziska]

Ouch is there any tricks to getting a better cold measurement? Id rather not button the engine up without being damn sure its correct

[Nails]

I wouldn't expect much higher than that, cold -- especially if unseated rings. I think you'll need to put it back together and test it warm. What else are you going to do now anyway?
Starting it to warm it up is the best part of a rebuild. You just never know --- but it usually turns out great.
Like they say, life is like a jar of jalapenos: what you do today might burn your ass tomorrow.

[edit: I misread your post and thought you were getting 90lbs cold. It won't start with just 60lbs. My bad. I still suspect a faulty test. Are you using an threaded extension tube -- the push-in expansion units probably won't get it with these deep wells.]

[Van Voyager]

At the risk of asking a dumb question: are you holding the throttle WFO while performing the test?

[GrandpaDenny]

I presume you're using a compression tester with threads, rather than the push-in kind?