136/137psi on cyl 3

[Cooked]

Hey Folks..

I have finally been able to do a compression test on my 82 650E (15K miles).

My clymer manual says anything below 140psi should be looked into. The results to my dry test (with carbs off.. and not warmed up) is;

CYL 1- 145
CYL 2- 145
CYL 3- 136/137
CYL 4- 140

Should I be concerned? Should I do a wet test? If so does it matter what type of oil I use?

Thanks for your time!

[Dave8338]

Hey Folks..

I have finally been able to do a compression test on my 82 650E (15K miles).

My clymer manual says anything below 140psi should be looked into. The results to my dry test (with carbs off.. and not warmed up) is;

CYL 1- 145
CYL 2- 145
CYL 3- 136/137
CYL 4- 140

Should I be concerned? Should I do a wet test? If so does it matter what type of oil I use?

Thanks for your time!

Sounds like if anything, you need to check the valves (#3) though, the bike will run just fine the way it is. Wet test is only done when the rings are suspect. With 15K on the bike, unless the PO never changed the oil, this should not be an issue in your case.

[rustybronco]

Hey Folks..


Should I be concerned?
Thanks for your time!

No.........

[Nessism]

Readings seem fine. And yes, check the valves if you have not done so already.

[tconroy]

Stick it back together and ride the #!#$ out of it!!!!

[t3rmin]

Another vote for check those valves. After doing the valves on my 650 it made such a difference in compression that the crank was noticeably harder to turn by hand.

[chef1366]

Those numbers are fine. Ride it!!!

[Cooked]

Three votes for yes... and three votes for no... anyone want to be a tie breaker?

I ran a quick search on the forum and from the comments I am seeing checking the valves aren't overly difficult... can't check my manual until I go visit the bike though.

If it is a easy job perhaps I'll do it... but that leads to the question... how difficult is it to repair any issues? Perhaps this is a different ball game?

[robertbarr]

There's only a 7 p.s.i. difference between the highest & lowest readings, and that's only 5% of the average compression. You're in fine shape.

[Steve]

Should you be concerned about the difference in pressure? No

Should you check the valves? Yes.

How long have you known the bike? Unless you knew the previous owner and have a history of service performed on the bike, you would be smart to check the valves. Valves do the most changing (which requires the most adjustment) early in their lives. This includes new engines or newly-rebuilt heads. After the factory-recommended 3,000 mile intervals, if you don't see the clearance changing, you can stretch out the intervals.

When the clearance does change, it will decrease. This will decrease the amount of time the valve is on its seat, holding in pressure and transferring heat. Your compression numbers can be lower and the likelihood of burning a valve increases dramatically. It's not that hard a job, nor does it take very long. The first time you do it, you will take more time finding the right tools, and also take more time reading the book to make sure you are doing it right. You should be done in under two hours. The last time I checked valves, I was done in about 45 minutes.


.

[jetta90]

Those compression numbers are fine.
Check valve clearance for sure to ensure they are within specs - my bet is number 3 valves will be a bit on the tight side.
Once done your bike will thank you with outstanding performance and reliability. Once again, those compression numbers are good and most importantly they are very even right across. Indicates all 4 pots are wearing evenly. That is a good thing.

[renobruce]

I'd say your fine, too. For a more accurate assessment of your compression, you should check it when the motor is warm.