Here's my problem. My buddy has a 250r, not sure what is done to motor, but has a fmf fatty pipe. It ran good on choke, but when the choke is turned off it would run for about 3 seconds then die, regardless of throttle position . So we turned the flathead screw in all the way(in rear of carb),and it would actually idle and rev good, butwould have absolutely no power to take off, would just want to die.Put the choke on full and it would run good, and had lots of power, but would kinda load up with fuel after a while.Checked the main jet,...340, put in a 380, and it didn't have any power either way, except maybe 1/10 throttle. Also the needle that we have was sold to us by a honda shop, but I believe it is fatter than the old one that broke, although I don't think it ran good with the old needle, either. It is set all the way up(last clip position from blunt end).Someone please help us out here.

 

You say it runs w/ choke on but will die when you shut it off. Has the machine been sitting? Sounds like a dirty carb if thats the case. When did this all start? Was there a mod installed and now you have a running problem or has everything stayed the same?

 

My buddy bought it a couple of days ago and he has no clue about this machine.The carb hasn't been cleaned in awhile, and from what I here it sat up for awhile. I told him to soak it in carb cleaner tonite, and spray all the orfices tomorrow.(Sounds kinda gross, but...)anyway the only other thing I can guess is that it has the wrong pilots, or that big needle(had to ream out that little hole just to get it to fit)....But, I don't really think the needle would affect the full throttle power.....I'm just plain confused..??

 

Any ideas?

 

first of all what carb does it have the mikuni ? round slide second the needle should never be all the way down in the main jet has the greatest effect in the half to full throttle

the number of the mainjet stamped on the bottom or side of the jet indicates the relitive size of the hole in the jet which meteresfuel the larger the number on the main jet is the bigger the hole

making setting changes carb settings are made by changes or adjusting four carb components

four components, the jet needle,main jet,and slow jet regulate the flow of fuel;air screw regulate the flow of air

1/8 to 1/4 throttle air screw and slow jet also jet needle straight section 1/4 to 3/4 jet needle (clip position) main jet half to full throttle

if you reamed out the main jet you had better take the carb to the honda shop and order the main jet and needle as a pair they are made to work as one

never i say again never put the clip all the way up when let off the throttle the needle slams all the way down in the main jet hense cuts off the fuel but the motor is still turning at a high rpm thats the fastest way to burn down your engine from the lack of lubrication

and alot of people dont understand using to much oil in the gas mix makes the engine run LEAN

*check the compression check for a good spark pull the fuel shut off valve out and clean the tank inspect the tubes for being pluged up
get the right jets needle and slow jet in the carb

SET THE FLOAT LEVEL clean the gas tank out install a inline fuel filter buy a good 2 stroke oil I use a natural bean oil 100 % natural

I mix 3 1/2 ounces to the gallon super unleaded fuel dont use oxygenated fuels bad bad will burn your machine down
make sure all the little holes are open I use PB blaster on all my o-rings ect to keep them soft

hope this helps Good luck

 

No he reamed out the hole in slide cause the needle was so fat

 

The air screw ?? well that may as well be a piece of scrap now i suggest he find a diffrent carb for the machine I put

a Keihin PWK38 on my 1984 Honda trx 250R took the air box off installed a long sock didnt do a thing to the jetting

carb came from a Kawasaki kx250 i would suggest maybe starting over with a used carb if it were mine
Good luck

 

Keihin 38 air stryker is great,but hard to tune if you never tuned one.