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  1. #1

    Polaris Sl 780 rebuild and running hot on stator cyl.

    Ok, had a sl780 with 100 psi on the stator cyl. Pulled all cylinders and found that they center and pto looked fine. #1 was gaulding but the ski has been sitting for 9 years without being properly stored. Owner just started it with a crankcase full of oil. Anyway Honed number one and put it back together started the engine and while running on a hose # 1 is running 150 degrees # 2 is 90 #3 is 100 .. I normally would not pay this much attention to one but since it melted I figured I would check.. Anyone ever ran into this before? I am pulling the carbs tomorrow.. Not a tard either the head gaskets are on correctly.. The Pictures are of the previous piston.
    Last edited by gvnitup; 05-29-2010 at 08:11 AM.

  2. #2
    Join Date
    Apr 2007
    unless you disconnect the main water into the motor and hook up a hose there ,you cant get a true head temp reading....
    with it hooked up ""flush ski " style very little water gets to the front cyl..
    your temps still look wierd...
    can you back it down in the water and run on the trailer and get some temps

  3. #3
    Ok, dropped it in the lake today (Left it on the trailer). Compression was 120 on all three cylinders. Let it warm up a second, then pulled one hard chop. Engine only went to 4200 and I shut it down. All plugs are grey, compression is now 110 on all three.. Didnt check temps with a gun (forgot it).. Brought it back home and pulled the carbs I am going to build them tomorrow, kinda puzzled on the grey plugs.. Anyhow, Will check the carbs Post back.. Not real sure why wot was 4200.. Only thing I know for sure was previous owner replaced the circut board himslef. I cannot think of anything to limit the engine to 4200 can you?

  4. #4
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
    Join Date
    Oct 2006
    Cleveland OH
    4200 is the limp mode RPM.

    The previous owner replaced the board himself?


    I'd be looking for an elec problem.

    Low fuel, low oil, and overheat will trip limp mode.

  5. #5
    I thought limp mode was 3500.. I kinda thought it might be from the board, but no lights are on.. Could have unplugged mfd I guess.. Hate to take the box apart, but guess I have no choice. Any idea on what wire being wrong would cause limp mode?

  6. #6
    Ok, pulled the carbs and found that the mag cylinder had a screw back out not letting the diaphram function properly. Which totally explains why it killed that cylinder. I took pics for all to see.. But after building, running the engine on a flush hose max rpm's were still 4330 no lights full gas and oil etc.. Wtf?
    Last edited by gvnitup; 05-29-2010 at 08:11 AM.

  7. #7
    Btw the screw that came out is in the far right picture..

  8. #8
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
    Join Date
    Oct 2006
    Cleveland OH
    So you are now past 4200 RPM. Good.

    Check the jets in those carbs.

    That screw that backed out, was most likely from someone else inside the carbs.

  9. #9
    Well NO, i assume it was still 4200, dont trust the mfd to be accurate. It said 4330 but was bumping the rev limiter or was only going to that. Shouldn't it hit 6250 on the trailer out of the water?

  10. #10
    Ok, well I kinda figured it out today. My customer installed his own circut board. In doing so he hooked up a few wires in the wrong location. Although it ran it was limited to 4200 rpms. I unhooked the grey wire and it's balls to the wall. Any diagrams anywhere on what wire goes where? This board does not Match the wiring..

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