I have an 05 250ex. Just added a full hmf exhaust system, and a uni air filter. No other mods then that. I've been looking around this forum alot for info on the lil 250, and what i've come up with so far is pretty much just change the main jet to a 110 or a 112, and that should do it. Now that fine a dandy, but im askin my question bc, hmf sent me a 125 kenith jet to replace the stock jet for my 250. I live at sea level and ride there as well. I have no other mods other then what was listed. I beleive this is going to be to big. What about you? And is there any need to mess with the clip on the needle? Thanks ahead of time.

Bryan

 

Hi there I am in the same boat as you with my 02 250ex. I just installed a full HMF and uni and the info I got was to move the needle down to the last clip and put in a 110-112 main jet and I did so and this thing still does not run right. It idles good and it has more power but when the rpm's get high it spits and sputters. And on deacceleration it back fires. At idle when you rev it it will backfire and shoot a flame out. So if I were you I would move the needle down to the last clip which should be the 3rd position or if yours has a 4th position that would even be better and put that 125 main jet in and let the rest of us know how it runs.

 

Okay, did some testing today. Put the 125mj in last nite, was a pain, had to take the hole bowl of the carb off, anyway this jet is WAY too big, even with the air box lid removed it still spits and sputters. I have not moved the clip on the needle yet, but i think i might have to, bc when you hold the front brake in and give it about 1/4 to 3/8 throttle it starts to break up. Im going to get a 110 and an 112 tomorrow and will try them as well. But i know the 125 is to big. And from my understanding with what lil bit of mods i have, as far as the needle in the carbs goes, you should only have to move the clip down one position. I will try that and will also post my results. Thanks again.

Bryan

 

I have an 06 trx450r with a DG x2 slip-on pipe(pretty much gutted) with a velocity air intake with K&N filter and no air box whatsoever. I have recently put a dynojet stage 2 kit with 140 main jet and my needle setting in on the 5th setting from top of needle. My fuel mixture screw is 3 rounds. My problem is that I am still breaking up a little on the holeshot. no mid range problem, but at full throttle it is breaking up really bad. it wont even pull with throttle wide open. I have to let off of it to get it to catch up. Some one please help. I have a big riding event coming soon. THanks!!!

 

bryan I was told that your needle affects your mid range

 

Aight here's what ive got. I went a purchased some jets ,110, 112, an 115. I tried the 110 first, left the needle clip in the stock postion( bottom groove closest to the needle point) and turned the air/fuel screw 1/4 turn out. It runs alot stronger no more hesisation, and backfires. Will do a plug reading the next time i get to ride. Im also making all my jetting setting with my airbox lid on. And as far as jets go, i dont like nor do i us dyno jets. I use kenith jets which is what come stock in all hondas i believe.

 

I would love to know the outcome of your jetting set-up and how it runs. I am in the same boat 250ex-hmf full pipe. As you can read in my other reply I am having alot of trouble with this too. I am at a 110 main and the needle is in the 3rd position and I have tried alot of A/f screw settings from the oem 2.5 to 3.5 out and I am currently at 2.75 out and my old reliable 250ex runs like junk. It is pretty good at idle through 3/4 throttle but on the top end it sputters and on deacceleration it backfires badly. It drives like the rev limiter is 3000rpm's earlier than before. if you get it figured out or you could help me in anyway that would be great . thanks.

 

Ok, my 112 has yet to still come in, and have only ridden for a few mines to check how everythings running. With the setup that i listed last time i have no ill effects with my quad. There is not backfiring, no hesitation or anthing. I am also located at sea level, i know the elevation changes can make a huge diff in how a quad runs. Now hybridtheoryd16, im not exaclty sure why your having probs. I pretty much have the same setup as you do. Did you bike run fine b4 the pipe? Did you try running the lil 250 after you put the pipe on b4 you made your jetting changes? If not i would setup the carb back to stock and start there. Then just change your main jet to a 110. Ride it, and see what happens. And as far as mine goes im assuming that the jetting is pretty close, but i still have yet to do a plug reading. But im thinking that since im leaving my airbox lid on then the 110 sould be sufficient. Let know what's going on and ill try to help as much as i can.

 

for the guy running the 140 main ... TOO MUCH FUEL you are running rich , try removing your air box lid see if that helps or drop the main jet size to maybe 130.... 140 seems far too big and backfiring means rich