anybody done a compression test to a cr 500

[BANSHEEFWI]

hi i have a cr 500 engine in a trx 250 and finally get a modification done to the kick start to start it .but i found dat it ain t had much compression when i try to start it .i get 90 psi i m at sea level .the compression tester new and i use it on my shee already .so let me kno wa i m suppose to get and the cylinder has a full drag port job done to it .thanks

[DirtDemon]

I'm not sure how much comp. it should have, it varies thoughout different model years, but 90 psi is way too low.

[quadracer87]

thats way to lie should be 170+

[FPMXer]

90psi is too low to run any bike. Put some new rings in her and it will be okay. If the cylinder is scratched with grooves then a bore job is needed.

[fourtrax250r]

yeah that sounds way to low. sure you kicked it fast so the air didnt leak thought the rings? on a side note i saw this on ebay. i wish i could have been there see them try to do this....

"I LEARNED A VALUABLE LESSON WITH THIS MOTOR: ALWAYS GET THE COMPRESSION READING WITH THE MOTOR IN THE FRAME! I TRIED AND TRIED WITH ANOTHER GUY TO GET A GOOD READING FOR ALL YOU POTENTIOAL BIDDERS. IT WAS ABSOLUTELY INSANE! BOTH OF US ENDED UP WITH BUSTED ANKLES AND WRISTS! (YOU CR500 GUYS KNOW WHAT I MEAN) THE POINT IS, THIS MOTOR HAS REDICULOUS COMPRESSION."

http://cgi.ebay.com/ebaymotors/ws/eB...180918329&rd=1

[CR480R]

Are you cranking the engine with the throttle wide open? It should be... The two stock 500's I have tested were getting around 150psi..

EDIT: The drag port could also be affecting the reading... Rings are cheap... May as well change them

[flotek]

it should be around 160-170 ,theres a problem

[semiwrench]

when a cylinder is ported to drag race the exhaust port timing is usually raised a bit, which would lower comression when the motor is kicked over, but the pipes sonic waves overcome this, filling the cylinder better a high rpm,s. However i,d pull the pipe and reed cage and take a peek at the damage.

[FPMXer]

Originally Posted by fourtrax250r

"I LEARNED A VALUABLE LESSON WITH THIS MOTOR: ALWAYS GET THE COMPRESSION READING WITH THE MOTOR IN THE FRAME! I TRIED AND TRIED WITH ANOTHER GUY TO GET A GOOD READING FOR ALL YOU POTENTIOAL BIDDERS. IT WAS ABSOLUTELY INSANE! BOTH OF US ENDED UP WITH BUSTED ANKLES AND WRISTS! (YOU CR500 GUYS KNOW WHAT I MEAN) THE POINT IS, THIS MOTOR HAS REDICULOUS COMPRESSION."

If these guys broke their ankles and wrists they have no business owning a 500cc smoker. Stupid people do stupid things.

[coolcatmat11]

My 84 cr500 had around 140-150 range... until I fryed a piston.....