what kind of mods do you have done?? if there is fuel into the boot between the head and the carb, that is normal. the fuel goes through that tube to get into the engine. what size jets do you have in there? tell me mainjet size, pilot jet, needle clip location and fuel skrew location if you know all of these. this page will enable you to look at everything on the 300ex, but there isn't any directions. check it out and click on what ever part you want to look at on the left side of the page: http://www.servicehonda.com/hard%20p...mes%20page.htm


how long has this problem been there?? did it just happen one day or is it after some modifications??

 

Lots of good suggestions. Wistech, I have seen that linkage you're talking about break, or become vastly out of time. It is adjustable via a tab you can bend. If it breaks, your butterfly will open with the cable, but the slide won't move until some time later. The primary symptom I have seen with this is a rich blubbery flat spot right off idle tho. Rangerrick63, you need to find somebody (a Honda dealer should have) with a peak voltmeter so you can visually inspect the spark plug firing voltage at the problem RPM. This should tell you for sure if it is ignition or fuel. One other thing that hasn't been mentioned is a plugged muffler. Wish I could look at your machine, I love a good mystery.

 

sounds like a jetting problem, i dont know much about it but i know there is a jet that is for top end one you ghet past 3/4 throttle? so whatever jet thats called is probably it cause if it idles its not a spark problem or getting enough gas or too much, lol i dont know

 

I have changed jets from stock up to 135, then down to a 130, when the problem still persisted, I went back to a 122 stock. I am not sure exactly when it happened, my son really didn't mention it as a problem, I heard it first on the trail. I really started hearing it cut out on him when he would ride at the track. I found water in the gas tank, I removed, & completely cleaned the tank, & strainer, no difference. I have installed a Cobra head pipe & muffler, so now I really notice it more than before. The fuel is on the filter side & the engine side of the boots, when I remove them. The plug only takes a few min's to foul out. I have installed a known good stator, & pickup, won't know it there is a difference until tomorrow. I am greatful for all these suggestions, & info. If the stator proves not it, I will pursue locating a tool to observe the spark. I plan on getting a different carb, just to see if it is something that I might be missing. Thanks again

 

make sure ur choke isn't on or half on!
sounds stupid but belive it or not i had the same problem for about a week till i realized it. make sure its all the way down and not half. From what u have said, thats exactly how my 300ex was acting.

 

Back when I was a lot younger, I had an old Can-Am 250 that normally worked well, loads of power (back then anyway) from idle til it just wouldn't rev any higher. Then, things got nasty. It started losing the top end, getting progressively worse. I tried everything, new ignition, carb tuning til I was blue in the face, you name it. The bike would start first kick, idle perfectly, pull through the bottom end and mid-range, then fall flat on it's face. I cut the exhaust open in desperation, cleaned the carbon and sh_t out of it, and it was miraculous, more power than ever.
With the baffles partially plugged in the exhaust, the engine simply can't pass the amount of gases it needs to get rid of at the higher rpm's. I'm not sure what the EX has for a spark arrestor, but my Foreman has a pipe plug on the bottom of the muffler for cleaning excess carbon out of it. I thought it was a water drain til I read the service manual.
To add insult to injury, my Jonsered 2041 went through the same antics a few years ago, to the letter. Did I remember the Can-Am episode?? Noooooo, I didn't.... until a few days went by and I had less hair than I started with. Again, cleaned the spark arrestor and it's off to the races again... or at least the woodlot.

Chilly

 

Now that is an option that I have not considered, but I will check it out. Thanks

 

I have the identical problem going on, did you ever get your resolved?

 

Well gong through this post and reading it, Has the problem ever been solved on your 300ex a lot of people has been have the same problem. please let us know thanks

 

Good luck getting an answer. This thread is almost 10 years old !