250EX mods vs. what jets?????

[Bigg Pimpin]

My ProCircuit T4, K&N Filter and pre-filter and jet kit should be here this weekend and I want to go ahead and slap it all on. This will be my first time jetting a carb. so I am not sure as to what jets to use and what adjustments need to be made. I know I can handle the work I just need a little detail on what to do. I plan to run the T4 without end-cap or spark arrestor unless I'm somewhere it is required and I'll be running without the airbox lid most of the time. The stuff is used so the needle and the 108 jet are missing from the kit but I guess I can get them from a local shop if I need them. So what jets should I change and to what? What other adjustments need to be made??? Thanks

[Bigg Pimpin]

BTW I thought a little info. on how it runs now might help. It's all stock with the exception of the end cap and spark arrestor being removed. Off idle it's a little sluggish kinda bogs a little then snaps right up. It runs good in the mid and upper rpm's but when I let out of it a high rpm it will backfire once or twice but that's it. When I am maxed out in 5th it doesn't seem to get as close to the rev-limiter as I feel like it should...like it just runs out of umph to raise the rpm's in 5th.

[cals400ex]

don't swap out jets from a jet kit to jets a dealer. i personally wouldn't have ever bought the jet kit and just bought the individual jets from the dealer. the jets in the kit are dynojets and the jets at the dealer are keihin jets. they are different. so, a 110 dynojet is NOT the same as a 110 keihin jet. if you have the directions to the jet kit, i would try to follow those. if not, i hope someone else that uses dynojets on a 250 chimes in. i dont' even know the stock size of the mainjet in a 250.

try turning the fuel skrew on the bottom of the carb out 1/2 a turn or so and that should help stop the backfiring.

[Bigg Pimpin]

Well after loking at DynoJet's directions and searching the BBS and a few other places this is what I am going to try I'll post how it works next week.

Remove Airbox lid, Replace stock filter w/K&N and pre-filter, Carve out the air snorkel hole from the tiny 13/16th hole there now, add T4 exhaust, Set the stock needle jet down 2 grooves, turn the fuel screw out 2.5-3 turns from snug and replace stock 95 jet with a 110 dyno jet. We'll see what happens.

[ryanh250ex]

Originally posted by Bigg Pimpin
Well after loking at DynoJet's directions and searching the BBS and a few other places this is what I am going to try I'll post how it works next week.

Remove Airbox lid, Replace stock filter w/K&N and pre-filter, Carve out the air snorkel hole from the tiny 13/16th hole there now, add T4 exhaust, Set the stock needle jet down 2 grooves, turn the fuel screw out 2.5-3 turns from snug and replace stock 95 jet with a 110 dyno jet. We'll see what happens.


hmm.....i'd go with something like 110 keihin....

i have a T-4 on my 250.....full system, but i have a completely stock airbox, lid on, and stock filter. i run a 100 main. runs like a raped ape, well, at least for a 250.

i also put my e-clip one notch down. i tried it at the 5th groove, and it ran very good as well, but the bike wanted to "blubber" at around mid-throttle and any time i would stop really hard or i would come to a stop (whether it was neutral or in gear) it would stall. very annoying problem. perhaps i could have cured it via turning in the fuel screw some, but it runs pretty good as-is....

back on topic.....the extra airflow may be enough to make you need to use the 5th groove.

it seems like most people with pipes and airfilters and some airbox mods run around a 108 or so Keihin jet....ask around, see what people think.

[Bigg Pimpin]

Well I ran the 110DJ with the stock needle set on the 3rd groove and so far so good. It could probably use a tiny bit of fine tuning but I am extremly pleased with the results. I got to race another 250 in the sand yesterday after he got about a 10 quad jump I gassed it and by the time I hit the top of 3rd I was passing him like he wasn't even there. :devil: