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Discussion Starter #1
hey guys i have a 79 enticer 340, i just rebuilt the top end recently because my compression was low. i have been running it for a while and it's been running really wierd so i decided to take a compression test and i got about 84 psi on both sides, any idea on where i could be losing compression or what to do. I know the tester is working cause i recently tested my 02 skidoo summitt 800 and it had 125 psi.
 

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Did you Mic the bore? Did you do a rering or did you do a bore job and new piston's and rings? If you did just a hone job and rering the cyclinder's can be worn beyond spec and may need a bore job.
 

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Discussion Starter #5
Did you Mic the bore? Did you do a rering or did you do a bore job and new piston's and rings? If you did just a hone job and rering the cyclinder's can be worn beyond spec and may need a bore job.
i took it to a proffecional and he bored out the cylinders and fit the pistons, they are oversize.
 

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How are you doing your compression test? Did you remove both plugs and pull it over multiple times with the throttle held wide open until the guage stopped moving?
 

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Discussion Starter #13
How are you doing your compression test? Did you remove both plugs and pull it over multiple times with the throttle held wide open until the guage stopped moving?
ya that's how i am doing them. I think the bottom end seals are probobly leaking they are thirty years old and never been replaced.
 

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If by bottom ends seals, you mean crankseals, they may be leaking, but they have no bearing on the engines compression. Low compression is caused by one or more of the the following:; bad, worn or damaged rings; pistons; cylinders; head gaskets; or cracks in the heads.
 

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Repair Shop Owner
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If by bottom ends seals, you mean crankseals, they may be leaking, but they have no bearing on the engines compression. Low compression is caused by one or more of the the following:; bad, worn or damaged rings; pistons; cylinders; head gaskets; or cracks in the heads.
You are correct sir!! :thumbsup: Bottom end seal will show no effect on the compression.
 

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Discussion Starter #16
If by bottom ends seals, you mean crankseals, they may be leaking, but they have no bearing on the engines compression. Low compression is caused by one or more of the the following:; bad, worn or damaged rings; pistons; cylinders; head gaskets; or cracks in the heads.
really i did not know that, so do you know how i could find out what the problem is? i think the pistons, rings and jugs should be good they are all new but maybe the heads are cracked.
 

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Maybe, or they are warped or the head gaskets didn't seat properly or who ever did the top end rebuild screwed up?????:dunno:
 

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Discussion Starter #18
i did the rebuild myself, it was my first rebuild. I am quite shure i didn't mess up. I think the head gaskets are alright though. I decided to take a comp. test today again but this time to let the engine heat up more before i took the test, and this time i got a compression of about 100psi. but isn't that still quite low.
 

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Did you run a break in period before you first tested the compression. It can take a little while for thing to seat in properly. Run it through another few heat cycles and then test it.
 

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Also, recheck the cylinder and head torques after. You mentioned that the crankseals are 30 years old, it might be a good idea to check to make sure you don't have any leaks or you may end up melting the engine down. The PTO side is usually the first seal to go and it's easily checked by letting the sled idle and spraying a little starting fluid or carb cleaner in the area of the seal. If the idle speeds up, you have a leak and should change the seals before any extensive use of the sled.
 
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