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  1. #1

    sl 750 project fuel problem

    Hello everyone, I bought a 94 sl 750 that was is peices. It is back together now, and running! Well it will start half the time, and will get about half throttle on the river, at that time, half throttle, it will die. If I prime the carbs it will stay running but will never go past half throttle. I rebuilt the fuel pump, no change. I have done a compression test, cyl 1 has 49 psi. 2 has 78 and 3 has79. My question is, can my lack of compression give me bad impulse vacuume and is that the result of my fuel loss when throttling up, or am I compleatly off base. any ideas would be greatly appreciated.

  2. #2
    Click avatar for tech links/info K447's Avatar
    Join Date
    Jul 2007
    near Toronto, Canada
    Those compression numbers are very low.

    Compression is checked with throttle held wide open, all spark plugs out.

    If those cylinders really have compression that low, you need to do a top end rebuild on that engine.

    If you haven't found it yet, click here for the Service Manual.

  3. #3
    Yes, like K said that is very low and if that is the correct compresion readings you should look into rebuilding the top end. Is it even hitting on all 3 cylinders? I am kind of suprised its running at all. I had cylinder go down to 80psi on my 94 SLT750 and it wouldn't even fire on that cylinder.

  4. #4
    I figured that compresion was low, and I am not sre if it is firing on all three. cyl 1 gets warm 2 stays cold and 3 gets hot. I would like to rebuild the top end, how can i measure so i can buy the right size rings?

  5. #5
    you'll need to remove the pistons/cylinders and check to see if any scratches or wear before you can determine what you'll need to replace and the size. if your cylinders have to be bored then you'll have to replace the pistons and the rings. a local machine shop could tell you if they need to be bored or just honed but you still need to measure for a proper size.

  6. #6
    I think you need to get another compression tester. I have never seen a motor with compression readings like that even run. How many hours are on the motor?

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