what is the compression suppose to bee

[bdtoady22]

just as above what should the compression bee on a stock 400 ex at wide open throttle cold?

[glamiskid395]

do you have a compression guage?
if so, put it place of the spark plug, and rollover the engine.

oh and alos check your manuel to see what the service limit is on a stock 400ex.

i dont have a manuel handy, otherwise i would tell ya.

[hornetgod13]

Run the engine and warm it up first. Than pull the spark plug and install the compression guage, hold the throttle wide open and crank the motor over until the guage maxes out (Usually 3 to 5 seconds of cranking) The pressure should be somewhere between 100-128 PSI.