Hello everyone,
Im very new to this sport and have a 1991 250x. I need to replace the carb and have narrowed it down to two options right now. There is a 400ex carb or a 38mm mikuni carb I can buy for this thing. I have been told that both will work. The mikuni came off a race 250x and the 400ex one is stock. Which do you guys think?

Thanks,
Corey

 

The 400ex carb is best, but it is bigger than stock,it won't work well unless you are running a pipe and modded air box to work with the extra flow from the carb. If you can find a 300ex carb, that will be an exact replacement for you.

 

Thanks for the reply. Im running a supertrap pipe, but have done nothing to the air box. I could work on that though, so get teh 400ex one instead?

thanks
Corey

 

Like I said in my pm to you, the 38mm is way to big and the 400ex carb is too much for a near stock 250x. I am running the 400ex carb on my 250x/350x engine and it seems to be almost to big and I have a supertrapp race exaust, k+n air filter and a modded air box lid. The stock main jet for the 400ex carb is 148, I have a 160 in mine and it burns perfect. But at top end it doesn't quite pull like it should, but I don't care because it will beat most piped 400ex's this way and it won't run lean so I will leave it alone since I hardly ride it. But the 400ex carb does work well with that setup but it is a much larger engine. I think you would have problems considering the size of the engine. But what do you have to lose if you give it a try. I can also tell ya that it is kinda hard getting that larger carb inside the intake boot. If ya try it you'll see what I mean. Try cleaning the carbs that you have, you will not be dissapointed in the performance of the stock carb. RUSS