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  1. #1

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    tech question about 750 sl 93

    hi im in the process of rebuilding a 750 an now it sort of ran for 15min now the frt cyl is all dinged up from what i think is detonation just needed some clarification

    the spark is blue but not very big arc is that good ?
    also it seems as thought the engine is was not geting fuel to 2 cyl frt and rear middle, ran but when i to ok the carbs off i noticed that the reeds valve had gas on them
    i already am going to rebult the carbs , just wondering about the gas on the reeds valve ?

    also is the engine able to run on one cyl i was pulling plugs to listen for a difference and when i pulled the middle cyl the engine stopped all the time ^?

    I did cut the wires and install new tips to the wires also triple pump and new lines have yet to install the restrictor waiting for the parts to make one . did notice that the reeds valve had little damage in the corner of 3 flaps will that have any effect it still coveres the hole


  2. #2
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by superfun123 View Post
    hi im in the process of rebuilding a 750 an now it sort of ran for 15min now the frt cyl is all dinged up from what i think is detonation just needed some clarification

    ... have yet to install the restrictor waiting for the parts to make one ...
    Did you go riding for 15 minutes without having a restrictor in the fuel system?

    On the trailer, the engine will run on one cylinder. Not well, but it will run.

  3. #3
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Quote Originally Posted by superfun123 View Post
    hi im in the process of rebuilding a 750 an now it sort of ran for 15min now the frt cyl is all dinged up from what i think is detonation just needed some clarification

    the spark is blue but not very big arc is that good ?
    also it seems as thought the engine is was not geting fuel to 2 cyl frt and rear middle, ran but when i to ok the carbs off i noticed that the reeds valve had gas on them
    i already am going to rebult the carbs , just wondering about the gas on the reeds valve ?

    also is the engine able to run on one cyl i was pulling plugs to listen for a difference and when i pulled the middle cyl the engine stopped all the time ^?

    I did cut the wires and install new tips to the wires also triple pump and new lines have yet to install the restrictor waiting for the parts to make one . did notice that the reeds valve had little damage in the corner of 3 flaps will that have any effect it still coveres the hole
    How about a pic of the dinged up piston?

    Blue spark should be good.

    Why do you think 2 cyls aren't getting fuel? Are they warm to the touch after running the engine?

    Reeds will have gas on them. It must pass through them to get into the engine.

    Chipped corners won't matter too much as long as the port is sealed.

  4. #4

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    yes i ran without the restrictor, the cyl that is damaged was really hot could not hold my hand on it the middle ran nice i could hold my hand for a few seconds and the rear was cold didnt run at all they all had gas on the reed valve but maybe not enough
    also the thermosthat was rusted shut do i need to reinstal it or can ir run without one
    Click image for larger version. 

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  5. #5
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    WTF is that?????

    It looks like something was inside the combustion chamber, but I can't believe the center of the piston isn't damaged.

    That's a new one for me.....


    Remove the thermostat.

  6. #6

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    it always reassuring when a seasoned tech says that's a first , but yes I removed the thermostat and order rebuilt kits and a restrictor hope that fix the problem

    I did find alot of pieces of the cyl stuck in the head but no cracks I'm going to replace the piston and own out the cyl even one when past the piston scuff it real bad the upper ring is stuck

  7. #7
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    All the damage is directly under the squish band. That's really uncommon.

    What do you mean you found pieces of the cylinder stuck in the head?

  8. #8

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    well small pieces of metal that seem to be piston were indented in the head

  9. #9

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    i was also wondering for the home made restrictor is says any jet between 60 and 100 what the best for stock engine ?

  10. #10
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Quote Originally Posted by superfun123 View Post
    well small pieces of metal that seem to be piston were indented in the head
    What pieces? Piston ring?

    Quote Originally Posted by superfun123 View Post
    i was also wondering for the home made restrictor is says any jet between 60 and 100 what the best for stock engine ?
    Keep it close to the 60 jet.

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