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Just bought a 97 TRX 300ex a few weeks ago. Ran though the motor and found cam and rockers were very wore down. So I ordered a new stage 1 hot cam as well as new factory rocket arms. Fired it up, rough running. Decided to rejet to a #125. The wheeler idles good now and has the power up to half throttle but as soon as I go to half it chokes it self. I'm wondering if I need to step up another size is jet. The next smallest I have is a 128. I also just installed a k&n filter as the old one was destroyed. The valve lash was set to what got cams had suggested. There is a little bit of a tick to the motor but I was told wasn't much concern. The guy I bought it from owned it since it was new and needless to say it was rude hard and put away wet. I've ran through the carb multiple times cleaning it everytime. What is my next best option? I adjusted the fuel mixture screen up and down and came up with the best idle, now I need someone help with the rest.
 

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Welcome to the forums! Sounds like main jet to small to me. Its been about 10 years since i had a 300ex but i for some reason think 128 is a stock size main jet? If so the 125 isnt gunna work for sure. They come right from the factory set lean to meet emissions standards. So you put even just an aftermarket filter on and its way lean. I would step up a few sizes on main from stock for just the filter. The cam will also have an effect on jetting. Anything that pulls more air in or pushed more out. Pipe, filter, cam, intake mods. Anything will have an effect on jetting.
 
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Welcome to the forums! Sounds like main jet to small to me. Its been about 10 years since i had a 300ex but i for some reason think 128 is a stock size main jet? If so the 125 isnt gunna work for sure. They come right from the factory set lean to meet emissions standards. So you put even just an aftermarket filter on and its way lean. I would step up a few sizes on main from stock for just the filter. The cam will also have an effect on jetting. Anything that pulls more air in or pushed more out. Pipe, filter, cam, intake mods. Anything will have an effect on jetting.
Factory is a 122 main jet. I'm going to try the 128 and a new plug. The next step up from a 128 I have is a 140 which I tried initially becuaae that's all the parts store had. That was very bad running.
 
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