I have an 02 300 ex that I recently purchased. I have gone through it and everything is now in good working order except one thing. It bogs down when you accelerate. It is ridable but not performing correctly. The carb has been gone through, new air filter (K&N with outerwear), valves adjusted, new plug and new top end. It idles and runs good, except when you put it in gear and take off, it bogs at the middle to high rpm range. I have changed the jet as well. I have tried from a .120 - .140 (stock is .122), it seems to run best at .135. When were riding over the weekend, the bogging seemed to get worse the more we rode, then seemed to get better when it coold down. Any suggestions, I need some help.

 

I think you are off on jetting. Running better cold would hint at running lean.

What does the plug look like?

 

I am already running quite a bit richer than stock on a stock quad. I have tried a .140 (I am currently at .135) and it ran worse than it does now. Still think it may be jetting??

 

sounds like needle higth needs to be adjusted well if ur carb has a slide in it

 

your main sound to big!!!

 

Anyone else have an idea on this.

 

I took the air box lid off and it runs like a raped ape. After purchasing the quad, I was going through it fixing and cleaning things, I seen that the air box gets it air through the frame. Whith the air box removed, I noticed that the frame was full of mud. I cleand most of it out but I am assuming that there is still a lot of mud up in the frame that is restricting the air flow. I will investigate further and post findings.

 

Still seems to be bogging without the airbox lid on, just not nearly as much. Does anyone know why it would bog out less with more air flow?

 

That would indicate it is rich.

Also, I screwed up on my earlier reply. Running better cold would also indicate too rich.

Have you looked at the plug?

 

Thanks Jeff, Now that you say that, all indicators point to being too rich. The plug is looks pretty black. Im gonna try the stock jet again. Last time I had the stok jet in, it ran worse than it does now. Any suggestion if that is still the case.