jetting question

[nnnon632]

Hey, i have a question about jetting for my 89' lt250r.
Its bored .80 over
has a fatty pipe, boysen reeds, and k & n air filter

we bought the bike used originally, had to rebore it since the bike blew up. When we originally had it the bike ran like sh*t. we checked out the the jets and someone drilled the main jet out. Afterwards we just put the stock jets in and it ran fine. towards the top end it just doesn't go anywhere so i know its running lean. the question is any idea what jet sizes i should use. all hinesty i dont feel like buying a bigger carb. if anyone can help i'd appreciate it.

[suzuki-guy]

i had the same problem and i just kept moving up sizes till it ran right. let me know how much you bored it. i bored mine sixty over if you let me know how much you bored it i can let you know what size you need.

[quadracer12]

the correct way to tune your carb is start rich (i would say start with 210 maybe 220) and lean the main jet until the bike will rev out. when you replace the jet, replace the spark plug. you can then use the spark plug to help with your tuning (if it is really dark and wet, you are rich, if it is white and not wet you are lean). If you want to get detailed you can do plug chops. Just want to confirm that you are mainly having trouble on 3/4 to Wide open throttle, because that is what the main jet controls. Anyway good luck.

[chazekxt]

a 210 or a 220 is to small. i had same mods as he does but with vforce reeds k a n no lid and a 260 main with stock carb....

[nnnon632]

i looked at the fmf jet center, they said 240 with just the pipe, on a stock bike so i was thinking maybe ill buy jets 250-280 and wing it.

[Camoman]

Believe it or not I'm running 190 main and 30 pilot in my 87 250r with a Uni filter bored .10 over and FMF slip on. Ran it this weekend ran good starts up 1st or second kick. NGK b8egv ceramic coating is a light brown...... I live in Ohio and elevation is 1100. ft

[LT250-R-MARTIN]

What Color Are Your Plugs. Cause I Kow My 87 Stock Main Is A 180. Leaner Is Faster Im Runnin A 150 Main In Mine With Ptr Pipe And Silencer And Weisco Piston Stock Displacement. You Really Need To Check Your Plug Color If Its Black Its Too Rick You Want It To Be A Cardboard Brown

[nnnon632]

my bike is running prime, but it won't go past 2000 rpm in 5th or 6th gear, and she cuts out in 3rd or 4th. in the lower gears its fine. when i look at the plug it looked perfect, the plug was a dark brown with a hint of black, not wet or to dark, and it wasn't burnt. so im believing she is starving under pressure, (remember it is bored .80 over/ to 270cc's)

[LT250-R-MARTIN]

Dose Nt Sound Like A Carb Issue. Do A Compression Test See Where Your Psi Is Your Rings May Be Goin On Ya. The Book Says Re-ring Every 8 To 10 Hours Of Ride Time Depending On How Hard Yo Ride Thats Where I Would Start

[LT250-R-MARTIN]

Also Check Your Reeds If They Are Fine And Your Compression Is Good You Might Try A Reed Spacer With That Bore