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  1. #1

    I body carb questions - after rebuild!

    I have been having issues with my 1999 yamaha xl1200. It does not want to go above about 4200rpm with out dying. I bought the ski with a bad cylinder, which has been replaced, and now has great compression. At the same time I replaced the cat converter with a O plate and sensor mod. I also added PV clips. I also rebuilt the carbs with new carb kits. I took out last summer to test and the dying problem showed up when I tried to ride the ski. So I decided that it was probably a carb issue and removed the accelator pump, drilled out the lo and hi speed screws, rejetted and added aftermarket FA. I used the tried and true setting from OsideBill's thread for my settings. Took it out last week I still have the same problem. I have pulled the exhaust and veified there is no blockage. Bypassed the fuel selector and checked all the lines from the tank to the carbs.Today I pulled the carbs again, and have gone through 2 of the 3 and everything looks good. The only concern was that the carbs are full of gas, I have not seen that before. I also noticed the new rebuild kit's (not Mikuni's) pump diaphram are really stretched out of shape. So can this be my problem? I not sure what effect that would have on the running of the ski. I did notice when I was testing the ski on the water, that when it started to die, if I pumped the primer it seemed to keep it running! From that I thought the carbs were not getting enough gas, but they were full of gas. For some reason it does not seem to make it to the engine. Does any one any thoughts on this? I am at my witts end. I will look at the third carb tomorrow, but not sure what to do to fix my problem. Do I order new Mikuni rebuild kits or do have a different issue. Not sure where to go from here. Could sure use some advise.

  2. #2
    Update, I have decided to rebuild the carbs again using Mikuni kits. I will see if this helps. The mylar material on the pump side is streched out of shape already!

  3. #3
    Moderator OsideBill's Avatar
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    Mar 2006
    United States
    after doing the carbs, if the problem still exists check to see if the PV motor is working properly. Also what is the compression of all three cylinders. And while you have the carbs apart check that the return restrictor is open and not plugged.

  4. #4
    New Mikini carb rebuild kits fixed my problem. Lesson learned no off brand kits for me! Thanks for everyone's help.

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