1981 XJ650LH - Compression Issues

Hi Everyone!

First post in this forum, but I have been lurking since I picked up my bike about a week ago.

Picked up a 1981 XJ650 Midnight Special for $200. This bike sat over on the coast for a couple years in a garage, and was covered, but the air was pretty harsh to it. Lots of corrosion that cleans up pretty easy.

My main issue is, I heard the bike run when I picked it up, but I had a really, REALLY hard time starting it over the weekend. I did dismount, and clean the carbs. Fresh fuel in the tank. I am getting spark on all 4 plugs. However, after about an hour, I did a compression test. Cylinders 1 and 2 are showing 0 psi. Cylinder 3 is at 65 and Cylinder 4 is at 60. I also did a "Wet" compression test on 1 and 2, and the reading did not change, which makes me think Rings. Basically, a complete engine tear-down/rebuild.

I'm thinking about cutting my losses and just putting the bike back up on Craigslist for the $200 and letting someone else pour money into it. Would it be worth it to dump the money into this engine? Or just save up a few hundred more and buy something that is in much better condition? Any advice would be appreciated.

Thanks!

 

Did you check the valves?
they could be stuck open which would cause compression to not be there?

 

@213 -

I did. Well, kind of. I turned the bike over with the plug out and saw both valves in both cylinders moving freely.

 

possiably just a bad gasket on the head then.
i would wait till fitz gives his words of wisdom but i would bet since your getting 0 , its probaly a blown gasket, but i could be wrong.

 

i would like to think if the rings where shot, there still would be some resistance , which leads me to beleive the valve was stuck open, which is letting all the pressure out, or the head gasket is completley blown out, which is letting all the compression out, but still would think it would read more then 0 psi.

just thinking logicaly here. somehting is open causing the pressure out, but where is the the question.

 

Totally understand, and I appreciate the insight. It's just weird that 1&2 have 0 and 3&4 are showing at least some compression. This test was done with no plugs in any of the holes.

 

was throttle open or closed?

 

I believe it was closed.

 

may want to retry the test, because according to a old thread i found, should have been open. just something to think about if you want to retest.

 

Fully charged battery, throttle wide open, let it pump at least five strokes on each pot but count up the same number on each one. I'm assuming you are using a proper tester with a screw-in adapter not the cheaper push in type that leak.

If the carbs have not been fully serviced (passed the clunk test and with no holes or tears in the boots) then take them off as they will affect the air flow to the engine by a different amount on each cylinder. Compression tests are comparative and to be meaningful rely on consistent conditions from one cylinder to the next.

Don't try to draw any conclusions on engine health till you have checked the valve clearances and re-run the test wet and dry with wide open throttle and a fully charged battery. So far your test method is unreliable.