help wit jetting on my r.

[250R4Ever]

does any one knows what size jet in need to use if i get my cylinder ported and polished(for drag racing) and if i have a fmf exhaust system?i also want it to run a little rich.

[tony_250r]

It mainly depends on the set-up. No one can really tell you what jet to run unless the have the same engine specs and runnning conditions. You'll have to do the spark plug test no matter what . I would start at 145 if I where you, stock is 142.

My power plant and induction system consist of, 3rd stage porting, bored stock carb, 7 White Brother air box vents, RPM exhause flange, K&N air filter with filter skins, WISCO pro lite 72 mm piston, radd valve, FMF Fatty pipes, FMF power core II silincer and I run VP C-12 race fuel with Klotz Benol 2-cycle oil.

I run a 155 main jet and I'm at the 2000' elevation.

[theeechozen1]

like most people i am mytholigical with my jetting, the best thing for you to do is fire that thing down the road full throttle in 3rd gear and kill it completely rapped out. then do your plug check to see where trailprotrailpro at, theres a thin line in jetting your machine just right , to be running a little rich you want it a dark dark carmel color, the lighter it is, the closer to having a fried top end u are. that is the only real way to do it--each machine is different and especially with a ported motor you will have to decide what to run on trailprotrailpro own-- hope this helps

[KASEY]

i agree with all i have read , heres an example my all stock 86 250r was running a 145 main put a fmf pipe on went to 150 runs greeat a little rich @ sealevel my 85 250r with porting pipe 38mm carb reed spacer and dual stage reeds is running a 170 main its jetted a little leaner than the 86 too @ sealevel, so there is no way of knowing what you will end up with without being there and doing the jetting

[250R4Ever]

ok guys thanks for the info., i knew that i was going to have to do the plug check but i was just wondering where i should start at. i bought a 155 main jet but its still reving up real high, so i didn't know if i needed to mess with the slow jet or not, but my 250r will rev up and won't shut off even if i try and kill it with the switch or spark plug wire. this is my first 250r so i don't know all i need to know about 2 strokes yet. thanks.........

[atc86r]

good luck dragging with stock carb. portwork usually wants bigger carb and filter.

[200x Basket]

ok guys thanks for the info., i knew that i was going to have to do the plug check but i was just wondering where i should start at. i bought a 155 main jet but its still reving up real high, so i didn't know if i needed to mess with the slow jet or not, but my 250r will rev up and won't shut off even if i try and kill it with the switch or spark plug wire. this is my first 250r so i don't know all i need to know about 2 strokes yet. thanks.........

i had the same problem. you are lean. that causes a hot spot that will ignite the fuel without a spark. you could have an air leak. do a search for this is crazy

[250R4Ever]

i have an k&n air filter on there and i just ordered an 38mm air stryker, i already did the search for air leaks i haven't found any so far, im going to put this carb and motor back together and let yall know what the results are. thanks.