engie365
beldenville wi
Joined: 10/04/2007
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I put my 03 Rev top end back together before Grantsburg with one new cylinder and new rings. They seem to not be seating because when I put it back together they had 100 lbs. compression. After running it a few times the new cylinder side had 125 lbs. and the old side had 100 lbs. After running it at Gransburg and now back at home everytime I check it, the compression goes down. It now has 100 lbs. on the new side and 80 lbs. on the old side. The motor should have 140 lbs. stock from what I have been told. I am just a new mechanic trying to learn. I have had it torn down several times and have not ever had this problem. Can anyone help me and tell me what might have went wrong. Once again thanks for all the help! i would like to have this running smooth before Wausau.
Thanks again,
Engie 365
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Doo-or-Dont
Ely, Mn
Joined: 02/12/2008
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Did you check the condition of your head gaskets?
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bobbygasser216
Mahtomedi MN
Joined: 08/08/2006
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Mark, are the pistons old? The Skirts could have colapsed. You can loose compression that way.try new pistons, I know they are costley but this might be what you need to do.
bobbygasser
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Leo dood
Egypt
Joined: 04/19/2006
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i could be wrong but i dont believe an 03 used head gaskets, they used o rings so check if those are stretched/crushed/tore etc...
also use skidoo mineral oil to seat the new rings......we have had problems with rings not seating with amsoil...
and how do ur cylinders look? scorring/ scratches on the cylinder walls? if there is u will have to get them re nicosilled however if there is scratches and they are below the ports that isnt hurting for compression because all ur compression is above those........that is somethin to start with.
let me know if this is usefull to yah
-Leo Dood Out-
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DooUDew
Shell Lake, Wi
Joined: 07/09/2006
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Try a new pressure gauge. I had a mac gauge that would give me a different reading each time i used it. Also, like Penders said, check the piston slop. Pull the head and with the piston at Top Dead Center rock it in the direction of exhaust to intake. It should rock some, but if it slaps around like a cheap dog in a brat bun, you may have to redo the whole deal. Re-nik and pistons.
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Leo dood
Egypt
Joined: 04/19/2006
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u shouldnt need new pistons tho if theyre rockin back n forth that is probably only rings because the piston centers the ring against the cylinder. all ur compression comes from the ring against the cylinder wall unless there is a hole in the top of ur piston lol...
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Doo-or-Dont
Ely, Mn
Joined: 02/12/2008
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Thats what I meant. O-rings. Oops. my bad. Ive ha problems when re-using o-rings on the head. They had slight tears in them and didnt seal well. Usually they are ok, but you may want to check them.
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glhperformance
downing wi
Joined: 01/20/2005
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actually the piston is what makes the majority of your compression. when the piston is heated up the clearance while it is running is about a .001
glhperformance
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DooUDew
Shell Lake, Wi
Joined: 07/09/2006
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The whole assembly makes the compression. Sloppy piston in the hole = rocking. How well does the flat surface of the ring work when its on an angle to the bore? Check out some old piston/ring pullouts. You'l notice the rings don't have the flat edges on them anymore. They are wore off on the top edge.
My 2cents:
Brand new piston, wore out ring = low compression.
Brand new ring + wore out piston = good compression with a very short life.
But anyway.. Did you find out what the problem was Mark?
#828 ljd
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bobbygasser216
Mahtomedi MN
Joined: 08/08/2006
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Mark Like I said. try new pistons. My 600 motor must have started to get a little hot from over reving, than my compresion started to fall off very gradualy, At the beginning of the season I had a rippin, fresh motor with 140 psi. and buy Frederic It had to slowly droped off all the way down to 115/120 and this is why I had been stuggleing with clutching so much prior to and that whole weekend. I was loosing powern slowly. I went from 66gms down to 61gms within a couple days, because my skirts were copapsing and loosing PSI,and power.
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