: Can anyone tell me what these compression numbers mean?



fristim
04-08-06, 09:07 PM
So I did a compression check the other day and heres what I got cyl:
1. 170
2. 170
3. 160
4. 170
5. 180
6. 170
7. 170
8. 170
Not quite sure why cyl 3 is so low, I'm thinking cyl 5 may have some carbon build up on it. By the way its a 98 concours with 169000 on it.

Ranger
04-08-06, 09:49 PM
They mean your engine is healthy.

parts68
04-08-06, 11:58 PM
I did a check on a 95 Rora Im fixing up due to being unloved
for some time.
All cylinders were around 200 except one was 185.
I decarbonized it because at first I had some that were at 225.
Funny that the service manual says normal is 140-170.

chevelle
04-09-06, 12:47 AM
So I did a compression check the other day and heres what I got cyl:
1. 170
2. 170
3. 160
4. 170
5. 180
6. 170
7. 170
8. 170
Not quite sure why cyl 3 is so low, I'm thinking cyl 5 may have some carbon build up on it. By the way its a 98 concours with 169000 on it.

They look excellent to me, especially for an engine with that many miles on it. Drive it and quite worrying.

dkozloski
04-09-06, 02:20 AM
The U.S. Air Force did some testing years ago on compression leakage vs. engine power and found there was no measurable power loss until cylinder pressure dropped below 35/80 measured with a differential leakage test. At idle speeds there may be enough leakage to roughen up the idle but at anything higher it makes no difference at all. With the pistons whizzing up and down there just isn't time for much leakage to take place. I've seen two-stroke motorcycles that were so worn out you had to tow them thirty miles an hour to start them but when once running wide open did just fine.