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  1. #1

    02 xlt 1200, compression 120, 119...........150???

    I have new to me stock 2002 xlt 1200, other than d-plate and stinger is gray, not black like motor. Ski was running 45 ish on meter and pv are functioning properly. I gave it a compression check and had the following: 3 was 120, 2 was 119, and then 3 was 150. This was with a trusted compression guage i have used for several years.....when i left the ski that day i thought to myself i have 2 low jugs and need a top end. But whiile laying there in bed for the evening it dawned on me triples should be 115-125 and 2 cyclinder is around 150ish. I went back the next day convinced i misread number 3. It was the same (cold engine, 160 hours). I have only seen this bump in compression when there was water in jug but this is dry and plugs all good color. I also have to assume anything and everything could have been done to motor but it is absolutely pristine with no paint on bolts. Any input? Anyone have this before. What if jug was done and no base gasket? Wouldnt it be soaked though and motor locked up with water and/or air leak? Ski runs great and sounds like it should. I have had gprs and xr 1800 and rebuilt a couple so i am familiar with engine.......thanks in advance!


  2. #2
    45 seems slow something is wrong should be closer or at 60. Not saying it's your motor but something wrong.

    My guess is if #3 popped previously then maybe someone bored the cyl and used a higher comp piston... Sounds weird for backyard work. Pull the head and have us a look.

  3. #3
    Yea I think I would take the head off for inspection of the cylinders to compare. Also I wouldn't worry about the mph on the dreamo, they are always wrong, gps with phone or handheld to see if ski is running optimally.

  4. #4

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    They don't really make higher compression pistons, and the head would have to be cut special on the front 2 cyl to get that much difference. If the base gasket was missing you would have water leaks cause the bottom of cyl would not seal and the head would not seal either since it is one piece and flat. Might want to check all three power valves, they being up or down makes a good size difference in compression. Like if #1 and #2 are stuck in the up position, the linkage between #3 and #2 is broken, and #3 PV is all the way down.

  5. #5
    Quote Originally Posted by LT1GMC View Post
    They don't really make higher compression pistons, and the head would have to be cut special on the front 2 cyl to get that much difference. If the base gasket was missing you would have water leaks cause the bottom of cyl would not seal and the head would not seal either since it is one piece and flat. Might want to check all three power valves, they being up or down makes a good size difference in compression. Like if #1 and #2 are stuck in the up position, the linkage between #3 and #2 is broken, and #3 PV is all the way down.
    The head could only be cut to drop the compression by cutting the dome out, which would drop compression. The compression on the first 2 is spot on and the head could not be shave on just one cylinder as it would never seal. This is also true of if there was no base gasket. Not only would it leak but the head wouldn't seal also. That's what is so baffling about this.

    The only thing I could possible conceive is a hot rod "rod kit" that had a slight variation in length? I know this is highly unlikely but something unlikely is at fault here. I know the next step is to pull the head but don't want to pull the head only to see a good piston and be out head gaskets......

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