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My Muffler Fell Out!!!

Discussion in 'XJ Technical Chat' started by day7a1, Mar 27, 2011.

  1. day7a1

    day7a1 Member

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    I have two questions for the exhaust experts.

    Background: When I got my bike it had 2 straight 2" pipes after the collector. It was LOUD! Way too loud, so I purchased some baffles and built a muffler that worked very well, and was almost too quiet (had several people tell me it was quiet, and coming off the freeway I had to check to see if the bike was still on). I'll share my design upon request.

    One of the baffles blew out the back yesterday on the freeway! Stupid me, should have secured it better.

    It sounds great now, I mean super stoopid sick. I love the sound. Loud, but less loud than most Harley's at idle, but opens up to a roar that I can still hear the wind and traffic (and F/A-18's at altitude, apparently) over.

    I'm honestly not sure if it's healthy or not. I know it's bad if the 4 headers weren't cross connected, but since they are I'm uncertain that it really makes too much of a difference. Plus, it doesn't sound uneven. It just happened, so I haven't checked my plugs yet, but that would be inconclusive anyway since a shaft seal rebuild is in the works (best thing I found for diagnosis, electrical contact cleaner...doesn't harm rubber or plastic, and works better than carb cleaner (which gave me a false negative, even though I had all the other evidence).

    The sound isn't nearly as important as the health of the engine, so what do ya think, guys? Keep it as is or rebuilt the baffle? (Not hard or expensive)
     
  2. schooter

    schooter Active Member

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    really, the only difference between running no mufflers after the collector box and running mufflers is an adjustment to the fuel/air mixture screws
     
  3. day7a1

    day7a1 Member

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    But I'm running one muffler on one side and none on the other. That's the problem I'm wondering about.
     
  4. schooter

    schooter Active Member

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    if you have the 650 with out the collector box i would think you could richen the 2 carbs on that side a tid bit.

    if you have a collector box that exhaust is going to find the easier way out and it will still affect all 4 cyls a bit

    do a plug chop and see what you're really at if theres a concern
     
  5. day7a1

    day7a1 Member

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    I guess I'll just keep an eye on it and re-sync. Not too many takers on this problem, is there? Perhaps it's time for a new set of mufflers! Too bad, I like these so much.
     
  6. dwcopple

    dwcopple Active Member

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    share your design please...you can PM me if you want to
     
  7. day7a1

    day7a1 Member

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    No need to pm, here goes:

    I took some cycleshack 2 inch baffles, $20 for a pair. They have a large opening and then narrow down to a throat with vents just like you would find in any muffler, I looked. If you do a search for "exhaust baffles motorcycle" they will come up, along with a bunch of other perfectly acceptable options.

    I welded a washer into the narrow part, and then one covering the large part, on both sides, can't remember which size, but it's the largest hole that would fit completely inside. Wrapped it in fiberglass packing (I used insulation from home depot) and stuffed it into the tube. Total cost was less than $30. Of course I already had the 2" tubes on the bike.

    I thought it was tight enough, and one is, but the other one apparently wasn't. The things come with a bolt and nut so you can attach it better, it's only my fault it fell out.

    I researched a lot on mufflers and found that 3 things deaden the sound: constriction, expansion, and absorption. My design has constriction from the washers, absorption from the fiberglass, and expansion from the fact that there ends up being 5 chambers total <--(5 |4 | 3 |2 |1 )<--.

    Using basic geometry I determined that the openings weren't overly restrictive, as the total area of the two smallest washer holes were larger than the area of a single exhaust header.


    There ya go! Any questions?
     

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