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  1. #1

    Crank index need help..

    Just curious, I have two 750's I put a new top-end on each. One does fine, other holed the pto cylinder again. All carbs built yadda yadda.. measuring crank index, I have found that if you get the pto cylinder at tdc #2 is a little diff than the other ski. I am buring the pto cylinder. Dont want to pull the engine unless I have to, but if the crank index was off wouldnt it have low compression? I will have a dial indicator tomorrow (left it at work). But isnt there another way I can at least eliminate this with some other method??

  2. #2
    Lake Mead Bum & BTLS Mark starflight's Avatar
    Join Date
    May 2007
    Boulder City, NV
    With any of the pistons at tdc, the other two pistons should be at equal distances down into the bore. Without the dial indicator, what
    you think is tcd, may be off by a degree or two, and will indicate that something is off.
    How far off do you think it is?

  3. #3
    I don't think it is, Both ski's measure the same.. Just checking everything carb looked fine but burned another hole.. Same Piston I rebuilt, just dont want another 1 bill mistke.. I am hoping the needle just stuck.. Am going to dyno tomorrow.. Try to update then..

  4. #4
    Ok, pistons are right on que.. No problems with indexing.. My problem is I keep buring the rear piston. i have totally rebuilt the carbs all new kits, needles, seats, etc. popoff is 16-19 psi. set to factory settings, new piston, cylinder, rings, NO crank seal leakage, intake leaks, or exhaust leaks. .. Took to lake after installing new piston again. Ran for 60 seconds after warming up, pulled wot for 30 and shutdown doing plug chops. The plug looked decent but didnt have the color of the others. The longer and harder you run it. The whiter it gets. I tried to take a picture of this and show.. I adjusted on the high speed jet and it didnt make much of a difference. I could go up in jet size, but have never had to on a stock ski before. Any ideas??

    The first two pics are of the plug I am having trouble with. last two are the other cylinders. Obviously the other two pistons I killed..
    Last edited by gvnitup; 05-29-2010 at 08:11 AM.

  5. #5
    Just fyi, notice how the first plug is getting white and flakeing? The first piston picture was from the engine failure. Has since been rebuilt. Second piston is the new wsm .025 over. It made it about 200 ft on the first hard pull.. Then it gave up..

  6. #6
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
    Join Date
    Oct 2006
    Cleveland OH
    What plugs are you using?

    If the crank is good, and the case is sealed, it would have to be fuel delivery issue.

    If this is a 650 or 750, do you have a restrictor installed?

    Have you checked the petcock and fuel hoses?

    Is the fuel pump in good condition?

  7. #7
    Sorry should have said. At rebuild I installed a new triple outlet fuel pump, new petcock, all new fuel lines. Yes reinstalled the restrictor. Fuel lines are new all the way to the sending unit. It's a 95 sl-750..
    I have been through the carb 3 times. Can't find anything, I have built 100's of these things.. I know I'm missing something.. Thats why I am back here..

  8. #8
    oh and bpr7es.. Thought about going to 8's

  9. #9
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
    Join Date
    Oct 2006
    Cleveland OH
    Use the 8's for sure.

    Can you visually see fuel flowing from that carb when running?

    If so, it's got to be sucking air from somewhere. Carb base gasket, reed gasket, rear crank seal.

    Check the pulse hose fitting. Mine worked, loose when I removed the engine once. Maybe it's sucking air from it?

    Is the head damaged by chance? Maybe it's creating hot spots?

  10. #10
    Havent run this thing with the covers off so I am not sure if its sucking gas down or not. This one still has the old style breather, makes it a royal pita to set anything also. I would upgrade, but still has the squirters in the base. I really dont think its sucking air possible head though. It did have some pits. I have never seen this affect one, have you? If pitting could be a problem this could very well be an issue.. Might need to pull the head and reinspect..

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