compression testing

[redsoxrule]

I got a compression tester the other day and wanted to know if it should be checked cold or hot, i tested cold and showed around 115-117 on each cylinder, the sled is a 94 vmax 600 twin...thanks.

 

[Sxr700Bandit]

Cold is fine. Some people say to hold the throttle full open while doing a compression check, but, imo you don't have to. Also, if you do it when the motor is warm, the piston and the cylinder will expand to their maximum tolerances.

 

[YAMAHIZAL700]

I hear its best to be done when warm because the pistons and everything expand with heat giving you a higher reading. For the hell of it Id try both and post what the results are.

 

[1badz]

Warm will give you exactly what you have under operating conditions, which is how I perfer to do it. You are looking just as much for variations from cylinder to cylinder however, so you will get that either warm or cold

 

[ski]

I recommend doing it warm to get full expansion of the piston and cylinder, and the reason to hold the throttle wide open is two fold. First it allows full flow of air into the cylinder to give a truer, more repeatable reading and second, it gives a much weaker vacuum signal to the carbs so you aren't flooding the engine with so much fuel while turning it over.

 

[daman]

You want to do it hot to warm with the throttle open,5-6 good hard pulls
each side..

 

[redsoxrule]

What kind of numbers should I be looking for, its a 94 600 twin with about 2300 miles on the motor?

 

[daman]

What kind of numbers should I be looking for, its a 94 600 twin with about 2300 miles on the motor?

If it's healthy it should have around 150,'94's had the thin HG.

ours has 145-150