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mobileblaster
03-21-2007, 07:33 AM
What should good compression be and at what psi do I know its low. Mine is not starting but is getting good spark and fuel. It just quit the other day while I was riding. the quad is old but has always ran good. I also noticed the slide on the carb on the side facing the piston is black. Is this normal wear?

C-LEIGH RACING
03-21-2007, 02:44 PM
What do those reeds look like, & if you pull the carb & reed off to check, get a flashlite & see if you can look down into the crankcase & see if fuel is puddled up down in there.
If it is, the engine is flooded & cant start.
Sometimes a loose flywheel nut & a sheared flywheel key will keep the ignition from sparking at the proper time & the engine wont start up.
Neil

mobileblaster
03-21-2007, 03:13 PM
what psi should the compression be though.

Barrymaxx
03-21-2007, 04:51 PM
If your in the 100-110 psi range, your gonna want to maybe throw in new rings and piston. Get they cylinder measured though, it might need to be bored.

mobileblaster
03-22-2007, 07:33 AM
thanks

mobileblaster
03-22-2007, 11:49 AM
yamaha told me the comprssion should be around 90psi with the throttle wide open. Does this sound correct.

noslofiveoh
03-22-2007, 12:00 PM
ive heard u don't want it to go much lower than about 115 psi...i could be wrong tho...what did urs measure out to be?

mobileblaster
03-23-2007, 07:38 AM
I comp. was 55psi. I pulled the top end was pulled. the bottom ring on the exhaust side was blown. the cylinder was not scored but I will hone it anyway.

stalefish_132
03-26-2007, 09:37 PM
thats not quite as bad as my friends blaster that had 46psi, over heated and burnt up a brand new wiseco. if you cylinder isn't scared up give it a quick hone and piston and rings and she will be running again.

ex kid
04-07-2007, 05:47 PM
110-115psi is the lowest you should go before a rebuild.