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  1. #1

    Need some XL700 help!!! Muffler comes loose after a few hours of riding!

    Bought this 1996 Yamaha XL700 and noticed the muffler bracket was missing bolts... I loosened the rubber water jacket boot, tightened the (2) clamps on the rubber gasket and the muffler lined right back up to the original holes and bracket.

    I then replaced all the bolts with grade 8 or stainless and after a few hours of riding, the bolts shear right off! Usually breaking inside the muffler housing or backing completely out and laying in the bottom of the tub.

    The ski runs perfect, no vibration that I can see or hear... it never fails, every time I replace the (4) bolts that hold the muffler on, they do the same thing after riding a few hours...

    Attached is a picture of what it looks like after a few hours of riding... no bolts, all of them either vibrate out or shear off!!

    I read about either having a vibration in the engine, or the cylinder head not being lined up first... but again, I do not feel any vibration, and I do not see why the cylinder would effect the position of the muffler since it lines up perfectly already????

    HELP!!!

    Click image for larger version. 

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  2. #2
    cyrillefrenchy's Avatar
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    blue locktite on all these bolts and they should stay tight

  3. #3
    I have used RED locktite, and GRADE 8... still break. These are not coming loose any more, instead they are shearing off! There must be some kind of crazy vibration to break a grade 8 bolt in half and leave the bolt still locktite in the hole!

    I'm at a loss... something is not right for all (4) bolts to break... the aluminium threaded hole in the muffler is getting so bad now, I won't be able to use the threads any more in the holes...

    Thanks anyways.. but locktite is not helping at all...

  4. #4

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    The PO probably stripped the holes out, that's why there were no bolts in the holes. To fix you will have to remove it, and drill and tap oversize. Loctite doesn't cure unless the threads are in good condition.

  5. #5

    I will try using spring bolts next...

    Quote Originally Posted by butterbean_29512 View Post
    The PO probably stripped the holes out, that's why there were no bolts in the holes. To fix you will have to remove it, and drill and tap oversize. Loctite doesn't cure unless the threads are in good condition.
    Yea the PO (previous owner) had the holes all stripped out and was using Standard threaded bolts!!! I completely replaced the muffler with another used one ($$)... holes and threads were perfect... I thought hot damn; the right muffler, all new Metric bolts, locktite, this baby is fixed... after about 4 hours all (4) bolts were sheared in half! (2) of them broke off with the threads still in the holes... I used an easy out and bought all new bolts and put them in again... bam!, same thing after a couple hours of riding... sheared bolts, etc...

    I had the bracket welded to the muffler today, and after talking with a guy at the machine shop, I am going to go with (4) longer bolts that hold the bracket to the head, and put heavy duty springs between the top of the bolt and bracket. He said the spring should take up any vibration and the longer the bolt the stronger it will be... like this:

    Click image for larger version. 

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    We will see what happens this weekend...

    Thanks again for the feedback...

  6. #6
    Myself's Avatar
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    There shouldn't be that much vibration. Grab the motor and push back and forth. Maybe you have bad motor mounts. Couplers must be loose, then bolt chamber down to cylinder with blue threadlocker, then install bracket bolts finger tight, then tighten bracket to chamber, then bracket to head. If anything is in a bind when tightened it will give somewhere. I've seen brocken brackets, and even cracked chambers.

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