LockedCompression PSI

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raxxor
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2010/02/24 16:51:18 (permalink)

Compression PSI

How much Compression PSI should i have in a 2005 Grizzly 660. I just did a compression test and im getting 90 PSI.

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#1

11 Replies Related Threads

    shaeleblanc
    Mud Pro
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    Re:Compression PSI 2010/02/24 17:29:23 (permalink)
    i am not sure what the norm is on the 660 but that is pretty low. my skis use to run in the 160psi with performance heads. i have not checked the quad yet. and my boat stays around 130... so i would assume the 660 should be around 130. what was your reason to run a compression test on the bike ? is it running poorly ?

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    #2
    raxxor
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    Re:Compression PSI 2010/02/24 18:12:43 (permalink)
    Yes it seems to die everytime it gets hot and the cooling system is fine.
    #3
    raxxor
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    Re:Compression PSI 2010/02/25 13:59:27 (permalink)
    Any ideas?
    #4
    Mason
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    Re:Compression PSI 2010/02/26 12:49:16 (permalink)
    yea thats way low. a stock grizz should have like at least 160. im pretty sure mine was pushing 180 somethin. a friendly reminder would be to make sure ur valves are good b4 u do the test again so u know ur not loosing nething cuz of that...bt if its that bad i dont c how itd run and have ne power at all 2 b honest...id look into the carb 2. maybe ur to fat and when the motors warm ur not lean enough, hence the hot start thats on all the 450s...or ur rings are so bad they're not stickin against the sleeve when its expanding from heat?...idk could be a lot of things i guess.

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    #5
    psychoracing
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    Re:Compression PSI 2010/02/27 08:59:22 (permalink)
    In the service manual I have it says 188 psi. if you take a cap full of oil and dump it in the cylinder just before you do another compression check if the pressure comes up alot then you have a ring problem, if its pretty much the same then you have a valve problem. check the timing to make sure it didnt skip timing on you alittle. I have seen chains stretch and slip a notch or so. hope that helps.
    #6
    NC08BB400
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    Re:Compression PSI 2010/02/27 09:27:40 (permalink)
    Check the valve lash first. The valves will tighten up when the eng. gets hot which will keep the valves open. This will also affect the carp. bc the vacuum through the carb is lowered. If the valves are good check the timing. The chains on these will stretch and jump one to two teeth on the cam gear. The eng may develop a backfire through the intake if it jumped two or more. I had a Grizz. 600 with these problems.
    #7
    billyj7175
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    Re:Compression PSI 2010/02/27 13:07:33 (permalink)
    X2 on check our valve lash...

    Same goes for the intake/exhaust....if you do a leak down test, you can put your ear by the intake or exhaust and listen for leaking pressure....that can tell you whether or not it's your intake or exhaust valves...

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    #8
    teamcovert
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    Re:Compression PSI 2010/02/27 13:23:15 (permalink)
    660's are really bad about the valves getting to tight and staying open all the time. I had mine about a year when it started getting to where it was hard to start and i had in another year like that when I went to adjust the valves that things was open like 1/16 inch at least.

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    #9
    raxxor
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    Re:Compression PSI 2010/03/01 16:06:08 (permalink)
    Well i did the oil trick and the PSI still didnt go past 90 PSI but after i opened the motor up i found the piston in perfect shape but my rings are way out of spec. If i remember right they should be about .015 and mine are .030. So i guess its a pretty good bet thats the cause of my problems. Once i get everything back together im going to be doing a plug chop to see whats going on with my jetting. I know when i pulled my spark plug it was covered in oil so im way rich. Could running to rich cause you atv to run hot also because last time i took it out it got so hot around the exhaust that it melted my trunk.
    #10
    raxxor
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    Re:Compression PSI 2010/03/11 19:02:23 (permalink)
    Ok i have another question my timing chain fell off the gear when i was putting the piston back in. Now what do i have to do to get the timing right?
    #11
    Vega
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    Re:Compression PSI 2010/03/11 19:19:50 (permalink)
    Take out the plug behind the recoil starter, roll it until the mark lines up, set the cam sprocket with the dots lined up with the head and the middle up.

    Wait for someone else to verify the cam sprocket timing, its been a while since I've done it.

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