Hey guys, hope you can help me out with a little problem. 300ex, K&N filter with a FMF Megamax 2.

I have been messing with all 3 carb adjustments for about 2 days now, and I think i'm getting really close. Im currently running a 132 main jet, the exhaust would backfire so I figured adjusting the fuel/air screw might clear that up, 1 turn out and it sounds great now with no backfire. I checked the plug to make sure it wasn't to lean or rich, and she is a really nice brownish tan, so I think im right in the range. The only problem I have is at full throttle, just the very end of it maybe the 9/10th end of the throttle or smaller, the engine will kind of cut out and go again. This occurs more in the 1-3rd gears, and 4th-5th are not really effected.

I have been reading up on stuff, and they say that the fuel/air is idle - 1/4 needle is like 1/4 - 3/4 and the main jet is like 3/4 full throttle..(this correct?) But does the mainjet work kind of in conjunction with the needle? The needle is still set at the stock position 3 clicks down I believe. When the throttle cuts out like that is that I think its an indication that she is running a little rich. Would adjusting the needle up one click to make it more lean maybe fix the very peak of my throttle?

I have a feeling that it should, but really would like to get some expert advice. Also removing the airbox lid doesnt really seem to fix the peak throttle spot im having trouble with.. But the plug shows its not lean or rich, so I'm not really sure what's going on.. If the needle and the mainjet need to go hand and hand, and just needs to be adjusted to correct this it would be a real time saver.

Anyhelp would be greatly apreciated, sorry I typed so much hope its not confusing.

 

Your information is correct re the pilot jet, needle jet, and main jet. Also, at full throttle all these jets are operating. If you have done a test ride at 3/4 to full throttle in whatever gear is practical for the conditions ( the engine doesn't recognize gears, only throttle openings). using a brand new plug, and find the plug in the color you mention. you then have the main jetting completed. The stumble at 3/4 throttle could indicate a slightly fat adjustment of the needle and dropping the needle to the 2nd position may correct it. Another test should be done to make sure. The stumble you mention could possibly be a lean condition on the needle instead, so if a second test doesn't clear up the stumble and/or makes it worse, then raising the needle to the 4th position would be the next step.
By the way, to do a really definitive test, it must be done at 3/4 to full throttle for at least 1/2 to 3/4 of a mile with no idling or low speed. Take a plug wrench with you to read the plug on the spot.

 

carbs

Just for more diagnosing tools [img]i/expressions/face-icon-small-smile.gif[/img]

Some pretty useful charts towards the end of the info.

 

Thanks hot_shoe_cv,
Happy to know that I am doing the right steps, I read up on lots of old forum threads and feel I have a pretty good handle on it. I did the plug check just like you said, I also read up on that on this forum. Thanks so much for replying I love this forum!!! I'm going to go down to the garage and adjust it right now, I'll fill yeah in on how it turns out.

Thanks agaiN!!

 

Hmmm... Still having big problems...

Adjusting the needle to the 2nd clip didn't help at all, and adjusting the neeld eo the 4th clip made it worse, engine would die and come back with like backfires really bad in the 3/4- up range...

I'm thinking it might be my main jet? What should I try next? Think I should go smaller or bigger? Should I get a new pilot jet? Thought I would have this all worked out, but I guess I have no idea what's going on anymore. Again anyhelp would be greatly apreciated!.

Thanks

 

OK,
I think I fixed the problem, I swaped the the main jet and the needle with a dynojet kit and followed the jetting specs that they recomended, and now it runs great with full power.

Later