Re: compression ??

[TC]

Tyler, Bob, I know the rear of the manual indicates 206 psi for compression but  I think that is a mistake, (of course I wouldn't be surprised if your 1260 cranks out numbers in that range Tyler). Actually, in the inspection/adjustment section of the service manual ... they show values for a warmed up engine to be standard 142 psi, minimum 128 psi and maximum 171 psi. They also show a maximum allowable deviation of 14 psi, (but I think that is excessive and would be surprised for anyone to find more than 1/2 that value without something needing attention.   I have always tried to record cold and hot compression readings every oil change since the bike was new .. So that I could tell when it was broke in and to have a record of the "normal" condition of the engine, (it is nice to know what "was"  normal when something is broke). I realize this may be unique to my bike but I have noticed that cylinders 2 and 3 have always recorded a difference of 5-6 psi when comparing cold to hot readings. Cylinders 1 and 4, (after break in), have never registered more than a 1-2 psi difference.    I averaged low 150s in Denver, (5000+ elevation), with a span of 150 low and 154 high, (hot readings). In Phoenix, (1150 elevation), I average 167 with a low of 164 and a 170 high, (hot readings).   This is a little over a 10% improvement at the lower altitude which is interesting ... since you are supposed to lose about 3% power for every 1000 foot increase in elevation ... well ... theres where it went !!    The "book" says to ground the spark plug wires when testing but you can also simply disconnect the pickup coil connector behind the battery to keep the plugs from attempting to fire .. etc ... campbell   ----- Original Message ----- From: Tyler Pennock Subject: Re: compression ?? > snip < > 206psi,throttle held wide open or will get false reading.