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  1. #1

    SL 750 Compression question?

    Hello, I have been lurking around here for a couple of weeks, and have found a ton of great information on the re-assembly my '94 SL 750. I have learned a ton, and think I have everying thing back together.

    I bought the Ski with the motor out, the previous owner "seamed" to know alot about these, he had 4 other similar skis in his garage. He had reassembled the engine, minus one cylinder jug and piston. I purchased a used jug, and got the motor put back together and just dropped it in today. I got all the hoses and wires routed and connected, and decided to do a compression test before actually trying to fire it up. I found that the first two cylinders had 130 and 131, which I felt good about, one of those was the replacement cylinder I installed, but then the last cylinder had 167 . I noticed on the head someone hand engraved B&P 168. I am assuming this is a modified head for high compression.

    What I wanted to know is what kind of problems will I have running one cylinder with so much more compression? Should I wait to run it until I can find a replacement stock head?

    Any advice appreciated. Thanks.


  2. #2
    ph2ocraft's Avatar
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    mark, WELCOME to the Green Hulk Forums!! I'd love to buy that head as I have 2 sitting in my garage waiting for a 3rd. I don't have a stock unit but I'll bet a lot of the guys do.

    With compression being that high on one cylinder you won't be able to run it on pump gas as it will detonate and possibly ruin that piston/cylinder/dome.

  3. #3
    Quote Originally Posted by ph2ocraft View Post
    mark, WELCOME to the Green Hulk Forums!! I'd love to buy that head as I have 2 sitting in my garage waiting for a 3rd. I don't have a stock unit but I'll bet a lot of the guys do.

    With compression being that high on one cylinder you won't be able to run it on pump gas as it will detonate and possibly ruin that piston/cylinder/dome.
    Thank you for the quick reply. I guess I won't be putting this in the water this weekend. I actually have one more head just like it that was in the box of parts I received. They look to be in excellent condition. I have no idea what they are worth, so you tell me, I'll gladly sell it.

  4. #4
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Welcome to the Hulk Marc.

    There are 2 different sized heads for the 750. Make sure you have the same 3 installed.

    I have a few heads for sale should you need one.

  5. #5
    Other than a compression test, how can you tell the size? I do need a head, let me know how much, I figured I might have to go to ebay for it.

  6. #6
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    I've got a a couple to sell if you PM me.

    The 93 750 used a lower compression head 25.6 cc while the 94 and 95 used a 26.2 cc head.

    If you can post a pic, I can tell you which you have by looking at the dome. An angle shot would be helpful instead of a looking straight down shot.

    The 93 has a large shallow bowl, while the 94 and 95 used a smaller, deeper dish style.

  7. #7
    Here are the pic's, the first two are the high compression heads, they are engraved b&p 163. The second two are what I am trying to match for the replacement.
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  8. #8
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    The stockers are the 94 750 heads. (higher compression than the 93)

    I've got at least 1 I know.

  9. #9
    I'll send u a stocker if u send PHO a BP?

  10. #10
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Quote Originally Posted by ZMANN View Post
    I'll send u a stocker if u send PHO a BP?
    Good call Z. I'll honor that deal as well.

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