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  1. #1
    Join Date
    Oct 2005
    Location
    french quarter
    Posts
    175

    Talking anybody done a compression test to a cr 500

    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 :blob5:

  2. #2
    Join Date
    Jun 2007
    Location
    Washington
    Posts
    1,104

    Default

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

    '86 TRX 500R
    Hand built frame
    '86 CR 500 motor
    Power Pros pipe and silencer
    Durablue rear axle
    38mm PWK A/S
    K&N filter

    '07 LTR 450 and an '04 TRX 450R, but we don't talk about those here.

  3. #3
    Join Date
    Jul 2007
    Location
    Nashua, New hampshire
    Posts
    1,107

    Default

    thats way to lie should be 170+
    1974 Kawasaki h1 500 tripple.
    Racing pipes, .20 Wisecos and Clamp on K&n's

    Sold The Quadracer

    88 blaster
    pwk 34mm carb
    .....................
    1982 250r - After market silencer - wiseco topend- +4 swingarm - 86 Front end -84 or 85 rear plastics and seat.
    2003 polaris predator 500
    uni airfilter
    Fmf Exhaust
    ..............

  4. #4
    Join Date
    Nov 2006
    Location
    Indiana
    Posts
    1,367

    Default

    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.
    My bikes

    Foster Bike
    00' Banshee (Shit my buddy don't ride it!)

    84' FXE Shovelhead

    72' Norton Chopper

  5. #5

    Default

    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

  6. #6
    Join Date
    Mar 2006
    Location
    Southern Oregon Coast
    Posts
    1,637

    Default

    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

  7. #7
    Join Date
    Oct 2004
    Location
    pennsylvania
    Posts
    14,217

    Default

    it should be around 160-170 ,theres a problem
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  8. #8

    Default 90 lbs compression

    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.

  9. #9
    Join Date
    Nov 2006
    Location
    Indiana
    Posts
    1,367

    Default

    Quote 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.
    My bikes

    Foster Bike
    00' Banshee (Shit my buddy don't ride it!)

    84' FXE Shovelhead

    72' Norton Chopper

  10. #10

    Default

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