2000 RM 265 compression?

[griffbones]

Is the piston really scarred or is it just burnished (slightly shined up)? The intake ports sometimes make burnish marks on the piston, as this is a very high pressure area, so it doesn't always mean there is anything wrong.

I agree with trying another tester! I recently thought I had low compression on a brand new engine and thought I had a perfectly good compression tester, WRONG! I checked my compression tester against another tester, and mine was off by over 40lbs.! Funny thing was I had just used it to check compression on another engine days before and it worked fine, so I guess a compression tester can take a crap on you at anytime.

 

[magneto]

How far are you above sea level? I believe that you will show less compression at higher elevations...

You can put a teaspoon of oil in the cylinder to temporarily seal the rings to determine if you have a ring seal problem. Don't use too much oil or you will get a false pressure reading.

 

[magneto]

Chart used to compensate for altitude when taking compression readings:

http://www.pelicanparts.com/techarticles/mult_Engine_Rebuild/mult_engine_rebuild-2.htm

 

[ckassen]

Well i am in Dallas....I am not sure what the altitude is(less than a 1000)....I talked to eric and he said the wear on the intake side of the piston is normal(as my last piston looked the exact same). I am going to see if I can find another compression tester to use...My friend used this compression tester on his chevy 350 with 400 crank(450 hp motor) and it registered 90PSI, I thought that was very low but he said it was ok(maybe it does read low)....

I did put a little oil in the cylinder and it seems to be at 150psi, once I run the bike it goes down to 130-140....I dont see how the rings could be leaking, everything looks good, but idk....

 

[ckassen]

Br8eg

 

[BigRedAF]

How far are you above sea level? I believe that you will show less compression at higher elevations...

You can put a teaspoon of oil in the cylinder to temporarily seal the rings to determine if you have a ring seal problem. Don't use too much oil or you will get a false pressure reading.

Very good advise. Just a few drops goes a long way, not needed if testing a warm / hot engine.

DFW airport is 607' above sea level, not a factor. Correction would be minimal.

If a good number for your bike is 185, corrected would be 182.

I had a gauge read 235. I knew it was broke because my bike would have been detonating. I bought a new one and it read 180.

 

[ckassen]

Well, i now really believe that the compression tester is broken....I started the bike up today(although its wet and cold) and drove it a little and noticed a slight ping, I think I am going one notch richer on the needle, hope it helps....

ping is with 89octane...I guess I have to go up to 93.....