My stock 1994 with 29,000 miles only has 140 lbs in both. Should I be bothered by that? YD

 

I believe the manual states >90, O.K. as long as both cyls within 10%. Always seemed like a huge difference, 150~90, to me.

 

If you've got 140 in both cylinders, you're good. It's not so much how high the number is, but that both cylinders are close to same compression. If there was a difference of 40-50 psi between the cylinders, that would indicate a problem. As Slammed stated, anything above 90 psi is acceptable, as long as both cylinders are within 10 % of each other.

 

Good to know...the bike runs great and I think it lived it's whole life with synthetics from previous owner.

When I first picked it up, it had a little weeping of the rear cylinder base gasket when cold, but switching to conventional oil (valvolene racing 20w-50), and letting the jugs warm up before riding, and 500 miles later, no more seepage. YD

 

Keep in mind that compression readings can and will vary depending on ambient air temperature, humidity, engine temperature and probably a couple of other variables. What you want to see is the same pressure in each cylinder. IMO, that's more important that the absolute number. I wouldn't worry a bit.

Altitude being a huge variable, since sea lever air pressure is around 14.7ps that your doing the compression amount conversion with, while someone up in Denver with 10.7psi air pressure is going to have lower compression numbers instead (10.7psi X 8.5 compression= 90.5 psi)

 

But my 93, rebuilt 10,000 ago, cammed and runs ****, and just tested has 115 in the front & 111 in the rear.

 

11 year old thread. 115/111 seems pretty low. That was a hot motor?

 

When a cam is installed in a stock engine that has more overlap and duration the compression will be less than it would be with a stock cam. The compression readings are pretty close between the cylinders so it is going to be okay.

 

Oh ok. THanks for the lesson.

 

Just a note for comparison sake:

When I replied to this thread back in 2013, my bike had the stock "N" cam. Now with the Comp Cams EVL-3010, the compression is at 165. Still 8.5:1 pistons but they are Wiseco instead of HD