# High compression



## Unclebill (Sep 4, 2009)

My 2005 brute timing chains jumped and bent all 8 valves so I replaced all the chains and valves. I checked the compression after I got it back together and I have 150 psi compression not 66 this is a completely stock motor Can someone tell why the compression is so high


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## NMKawierider (Apr 11, 2009)

You are super-sure the valve timing is correct..and someone didn't build it before you with some high-comp pistons.. That's some high readings for a stock engine. The only other time I have seen that is when there was enough air,fuel and compression to detinate as it turned over. That was on a race car with 13:1 pistons though. We had to evacuate all the fuel fumes and test it stone cold and bone dry otherwise we got readings from there to 500 lbs.

Anyway these are stock what..8:1 so there is no way it can go over 80 or so at best as long as all is normal. So...something...aint.


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## wood butcher (May 11, 2009)

are u remembering to hold the throttle wide open?


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## Unclebill (Sep 4, 2009)

Throttle wide open motor idles perfect no noises 
but has really bad spark knock when under any load


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## J2! (May 8, 2010)

That is really high. That's about what I have on my 840 with 12:1's..


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## gotmuddy (Jul 15, 2011)

maybe when you put your cams back in you messed up the compression release.


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## Unclebill (Sep 4, 2009)

I going to tear it back down when I get back home and see whats happening


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## wyo58 (May 13, 2011)

Valve timing aside, there is no way to get that kind of compression from a stoke motor. So either someone has slipped in high compression pistons, shaved the head, or your gauge is funky. The best a 8.8 to 1 will do at sea level is 66 psi. As you go up in altitude it is going to drop from there.


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## 03maxpower (Jun 6, 2010)

yeah my 840 is 160


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