2001 YZ250F only runs with choke on?

[1999RM125RIDER]

bike starts up and runs great with the choke on...i even rode the bike with the choke on and it's got lots of power...but as soon as i push the choke in it coughs sputters and stalls...if i give it gas it just bogs down...the bikes been sitting for a couple of years and i've already tried taken the carb apart and cleaned it and put in a new plug

 

[kta176]

Usually if your bike only runs well with the choke on you need to richen your jetting to compensate for the cold weather.

 

[1999RM125RIDER]

can the jetting be that far off that it won't even idle with the choke off...when i turn up the idle adjust knob so the bike will idle with the choke off, it bogs and stalls as soon as i give it any gas...what should i start with on the jetting...needle position? main jet?

 

[Ol'89r]

...the bikes been sitting for a couple of years and i've already tried taken the carb apart and cleaned it and put in a new plug

Clogged pilot jet or pilot air system.

Remove the pilot jet and make sure you can see daylight through the hole. While the pilot jet is out, remove the fuel screw and blow compressed air though the pilot jet hole and the fuel screw hole. The pilot jet has a very small orfice and it is easy to plug it up. If there is any sediment in the fuel, that can clog the pilot jet also.

Good luck. :cool:

 

[rmc_olderthandirt]

The fact that it won't run without the choke on means that the main circuit is running too lean. You could have an air leak on the intake manifold side or a clog somewhere in the carburetor.

You say you cleaned the carburetor..... Can you describe how you did that? I have found that what many people consider to be "cleaning" is nothing more than a cosmetic wiping off of the visible dirt.

The parts of the carburetor that need to be cleaned are the tiny passages that you can't get to or see. These passages are under/behind the jets and require a total tear down of the carb to have a chance, including removal of the jets. The carburetor needs to be soaked in a real nasty solvent for a while (like overnight) and then have the passages blown out with high pressure air. Note that the proper solvent is so nasty that it will destroy any gaskets or O-rings so you must be sure to remove them prior to soaking.

It is very common for an engine that has sat for a long time to have the carburetor get gummed up due to the gas evaporating out of the float bowl and leaving behind the goo that doesn't evaporate. The worst thing would be to have left the gas valve on so that an entire tank of gas gets evaporated down to a thick sludge in the carburetor. Second worst is simply turning the gas on every few months, kicking the bike to life then shutting it off without running enough fresh gas through to flush the carb out. All you have done is add another float bowl of gas to evaporate out, adding to the goo.

This goo settles into the tiny passages. The float bowl completely drys out and this goo drys out, turning into a hard varnish like material that can completely block a small passage.

If you haven't really cleaned the carburetor then do it again. If you don't have the really nasty carburetor cleaner (environmental concerns is making this stuff hard for the do-it-yourself'er to get a hold of) then you might be better off taking it to a shop and have them clean it for you.

If the carb is clean, then look for an air leak. Perhaps some gasket has failed or a rubber boot has cracked.

Rod

 

[76GMC1500]

I guarantee you the main jet is plugged. The fact that it dies as he rolls on the throttle tells me it's not a vacuum leak because manifold pressure is rising as the throttle opens and the leak should become less severe. You need to actually remove the main jet from the carburetor and blow it out with pressurized whatever. Don't try to poke things out with wire as this enlarges the jet. For the price of a can of carb cleaner, you can just buy a new jet as well.

 

[souphmars]

how long has it been since the valves were adjusted?

 

[1999RM125RIDER]

i just got the bike and i haven't adjusted the valves...i bought it from a friend and i was with him the last time the bike was ridden (at least two years ago) and the bike was running fine.

 

[1999RM125RIDER]

i have also taken the jets out of the carb already and cleaned them with carb cleaner (no compressed air though as i don't have it). Is the main jet the one that the throttle needle sits in when the throttle is closed? i'm fairly sure this jet was not plugged as i could blow through it easily. one other jet (the longer one with the perforated end) may have been clogged as i could not blow through it from the opposite end of the perforations, although i am not sure if you are supposed to be able to. sorry i don't have the names of the jets handy, my manual is at home and i am at work...i will update the posting later if the names will help

 

[1999RM125RIDER]

just checked the online microfiche...i believe it is the pilot jet that has the perforated end

 

[76GMC1500]

The pilot is perforated and the main sits under the throttle needle. Check your float level and check the float needle seat to ensure it is allowing unrestricted fuel flow.