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  1. #1
    Race, wreck, repeat delagem's Avatar
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    Fuel Line Restrictor, what next?

    Ok, so I had a talk with Randy today, and he said if there wasn't originally a restrictor in my fuel lines, then it probably was built into the carbs. I checked, and he's right. Never noticed them before.

    He took a nice pic, so I've attached it. I tried a pic as well, but mine didn't turn out so well!

    So I'm not missing a fuel line restrictor. What else could cause this hole in my piston? (oh, I checked, fuel filters built into carbs are absolutely spotless. I also run a large inline filter)

    Michael
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    Last edited by delagem; 07-16-2007 at 08:43 PM.


  2. #2
    ph2ocraft's Avatar
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    I didn't find your original post but have you checked one of the signs of a out of index crank??

    "Unexplained piston failure on one cylinder (ie severe detonation, broken ring lands, piston holing)"
    I know that's what I'd check first.

  3. #3
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Most people on here like to run BPR8ES plugs instead of the 7's because thy're too hot. What were you running?

  4. #4
    Im new to this site, trying to find out why my front piston keeps burning holes. your photo is exactly like mine. how do you fix the problem. i rebuilt carbs but dont think i saw that restrrictor and can it be fixed. thx in advance.

  5. #5
    Moderator beerdart's Avatar
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    Quote Originally Posted by delagem View Post
    Ok, so I had a talk with Randy today, and he said if there wasn't originally a restrictor in my fuel lines, then it probably was built into the carbs. I checked, and he's right. Never noticed them before.

    He took a nice pic, so I've attached it. I tried a pic as well, but mine didn't turn out so well!

    So I'm not missing a fuel line restrictor. What else could cause this hole in my piston? (oh, I checked, fuel filters built into carbs are absolutely spotless. I also run a large inline filter)

    Michael
    All Mikuni SBN's have the internal restrictor. The system requires another to keep pressure in the system.
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  6. #6
    Race, wreck, repeat delagem's Avatar
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    Ok, I just checked crank index, at least in my semi-redneck way. I used a dial indicator to put each piston at TDC and then used a digital caliper to measure piston depth. Did each piston 3x, and did each piston at TDC while measuring the other two. Nothing more than 0.40mm, so that's gotta be pretty close. (I wish I had thought to check crank index back when the motor was sitting on my bench! I always do a leak-down test, guess I'll get a degree wheel and make indexing part of my pre-install procedure as well)

    I am running PPR8ES plugs.

    Steve, I will try an additional Mikuni 90 main jet in the line, as I'm just pretty much out of ideas at this point. Does anyone else have any suggestions?

    2SL750, if you're getting a hole in your piston, it's usually a sign of running lean. You should have your carbs rebuilt, and replace your fuel pump. Those are the usual culprits.

    Michael

  7. #7
    twinstack1 twinstack1's Avatar
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    What year is this? (the ski I mean). I modified the fuel rail and installed 2 fuel pumps. 1 going straight into the pto, and one going to the mag cyl's. If yours is like the one I had, the mag cylinder is the last one to get fuel (fuel flows from the pto, then center, then mag) It's been years ago since I did this. Anyone else familiar w/what i speak of. I don't want to give out wolf tickets!

  8. #8
    Race, wreck, repeat delagem's Avatar
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    I know what you mean, they used to call that "daisy-chained" or something; all fuel from the pump went to the PTO cyl, then what was left went to the CEN cyl, and if anything was left after that, it went to the MAG cyl. That, coupled with my top-notch 16 liter/hour OEM fuel pump gave me a stack of burned MAG pistons my first year with the ski! (before I discovered these forums, that is)

    Mine is split with a Tee in between the PTO and CTR, and another Tee between the CTR and MAG. Two fuel lines from a dual outlet 65 liter/hour pump.

    Just got my new WSM piston in, big thanks to Jay at Atlantic Powersports! And to ZMann for the intake grate! My Mikuni 90 jet will be in tomorrow. Crossing my fingers!

    Oh, FYI even though Partsland shows a part # for the inline fuel restrictor for the later SL650 and 750, it's discontinued! I tried but couldn't get one.

    Michael
    Last edited by delagem; 07-17-2007 at 11:32 AM.

  9. #9
    ph2ocraft's Avatar
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    Have you tried that trick inline one crazya makes?
    Change the jets and alter the fuel pressure, pretty nice.

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