Could This Be???

[portero72]

having just completed my 3000 mile tour of mexico, and quickly coming up on 80k for the old girl, i decided to do a compression check and see what the future looks like for our relationship. tried it once yesterday. apparently i was doing it wrong. bike was warm, but i wasn't holding the throttle open. i also suspect the battery was weak, as it had sat for almost 2 weeks and was not cranking all that hard. yesterday, all cylinders read EXACTLY 100 psi. i was bummed, but puzzled, since it ran so well. so i added seafoam to the crankcase, changed the oil and went for a nice long ride today(ran like a champ!). came back, read up on the proper procedure, and tried it again(throttle wide open, battery was cranking harder). now for the amazing news-the readings varied, but were all between 152 and 160 psi. now i'm cautiously optimistic. my question is, can this be possible? it seems a bit high, even for a new bike, let alone one with 80k on her! i'm stoked, because it seems we shall continue our relationship, but i wanted to ask the experts. your thoughts are always appreciated. mark...... ps-my mechanic buddy and i did a comp check when i first bought the bike, way back at 28k, and 3 cylinders read above 150, with one a bit low(120ish), that he said was probably a stuck ring due to sitting for too long, and that a good long ride would probably unstick it. so i rode it from tx to az and back. it appears to have unstuck...heehee

[RUSH]

the psi seems right. You must have bought the bike made on a Wednesday.
How was the trip through Mexico?

[trbig]

You might run some carbon cleaner or some Marvel Mystery Oil in the gas for a few tanks. Carbon buildup can make your compression go up also... taking up room in the cylinder. I don't know if the seafoam cleans that... if so.. sorry.

Tod

[xs650mike]

Or Techron in the gas. My local auto mechanic is big on Techron for cleaning injectors and decoking engines. He likes MMO for freeing stuck lifters, worked for me.

[portero72]

i've used the seafoam in a few tanks of gas(and the crankcase, once) and gas additive frequently. don't misunderstand-i'm quite pleased with the compression readings, i was just shocked to find them so high.

[portero72]

RUSH-your humor is my cup of tea. ps, here's a link to the mexico journal. http://www.xs11.com/forum/showthread...5&pagenumber=1

[portero72]

anyone out there w/ a new-ish motor who knows thier compression? just wanna compare...

[Dennyz]

I have an oldish motor (125k) that measure 120 - 125 psi. I found I can get these number to be higher or lower, depending on the process. I am more concerned about consistency across the 4 cylinders. My "F" does not have the snap it once had or that of my "SF" with 20K on it. But, it is smooth and quiet. I have never tested my "SF".

[portero72]

mine were 152, 157, 160, 159. consistentent enough, i spose

[xs650mike]

Can't complain about those #s, darned good for an old bike. I haven't tested my SF but my XS650H was 143 & 147 right after I got the motor unfrozen. I should test it again now that it's been ridden a bit. Probably better, the motor seems strong.