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Lazy Exhaust/Rejetting Question

Discussion in 'The Garage' started by louis, Jun 19, 2016.

  1. Hi guys,

    1973 TX650, stock exhaust system, stock carbs, stock air filters and air boxes.

    I have searched the forum and read most of the threads on rejetting after putting on a new exhaust.

    I want to replace my stock '73 exhaust baffles with something different. I plan on keeping the stock airboxes, filters and headers, just changing the baffles. The stock baffles are very muffled, and about 25 inches long. If i replaced them with different muffled exhausts, will I have to rejet? Does the length of the mufflers have any impact on whether you have to rejet? I ride this bike every day to work and cannot be bothered pulling my carbs at the moment.

    Also, what diameter exhaust do these bikes need? Read in a thread 1 3/4, is that right?
  2. funky

    funky XS650 Junkie

    In my experiance I changed my exhaust to short reverse cone and had to rejet.
    The problem is that anything to do with carbs means that you have to take them off clean them set them up that means float levels have to be checked diaphrams checked all seals its a bigish job. rejetting is another problem as there are so many combinations as you have to deal with three circuits in the carbs, also location altitude have an influance on jetting .... Also the engine must be set up right valve timing ,timing chain, ignition timming all have to be spot on. i am still playing with mine two years later.
    By all means have a go but best left alone if you need the bike to run you to work.
    If you know some one who has a xs that has the mufflers you want to run ask what jetting he has and this will get you in the area you need. all the best Funky
  3. Cheers mate, did you change air filters when you went to short mufflers? I read on this forum if you are only changing exhausts you probably don't need to rejet.

    If what you say above is accurate, I won't be bothering and will leave the stock exhaust on.
  4. 5twins

    5twins XS650 Guru Top Contributor

    A lot would depend on the muffler you choose. If it's very open and free flowing, some jet changes may be needed. If it's not much more open than the original, you probably could get by with no carb changes. You have an earlier model and the carbs were set up a bit richer on them, so that is in your favor.

    Even if changes were required, they shouldn't amount to much, maybe an increase of one or two sizes on the mains. If you had to change the needle setting to compensate for the larger mains then a size up on the pilots may be required as well.
  5. ThatXS650Guy

    ThatXS650Guy More Sparky than Speed Racer XS650.com Supporter Top Contributor

    Louis I am about to begin to swap the stock exhaust (already gone courtesy of Mr. Sawzall) with 1 1/2" headers and Mike's commando cans. Everything else is stock so at the minimum there will probably be some fuel screw adjustments and perhaps some jetting changes. I'd be happy to share my findings...
    This is on a 1979 with the stock carbs and airbox.
  6. That would be great Jim.
  7. 5twins

    5twins XS650 Guru Top Contributor

    His jet sizes aren't going to match what you need. His '79 carbs are jetted totally different than yours and you use different style pilot jets as well.

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