Bike won't run unless choke on

[jack3835]

Hey folks,

My son and I were riding this past weekend, and way out in the woods, his 02 PW 80 quit running. I changed the plug, and that did not help. It was cutting out and acting like a fouled plug. I finally found that turning the choke on, would get it cranked and run for a few minutes, then die again. We limped back to camp, I checked the flow of gas, which seems normal, but unsure of next step.....Thginking of draining gas, cleaning carb, one more new plug....after that no ideas.....any suggestions....

[ButchWR250F]

Sounds to me like the pilot jet in the carb is clogged. If the air filter was just cleaned and oiled, over oiling can fill the pilot air passage with air filter oil and the pilot circuit doesn't work so well either.

Drain the fuel out of the fuel tank and look at it to make sure there is no water in it. Drain the float bowl of the carb and do the same thing. If there's water in there it will be at the bottom of the container you drain into, and it will keep together in a big drop. It's fairly easy to see. If the fuel is clean (no water) then remove the carb and clean it with spray can carb cleaner. Spray the stuff in EVERY hole you can find. Follow that up with blowing it out with compressed air. Put it al back together and it should be fine.

[Tubo]

Sounds to me like the pilot jet in the carb is clogged. If the air filter was just cleaned and oiled, over oiling can fill the pilot air passage with air filter oil and the pilot circuit doesn't work so well either.

Drain the fuel out of the fuel tank and look at it to make sure there is no water in it. Drain the float bowl of the carb and do the same thing. If there's water in there it will be at the bottom of the container you drain into, and it will keep together in a big drop. It's fairly easy to see. If the fuel is clean (no water) then remove the carb and clean it with spray can carb cleaner. Spray the stuff in EVERY hole you can find. Follow that up with blowing it out with compressed air. Put it al back together and it should be fine.

???

[1biglung]

Another idea to check is maybe vacuum leak. Try starting and spraying carb cleaner around the carb and see if it affects the idle.

[tjjordan]

All of your suggestions are good. Good chance a contaminant in fuel (water/dirt) may be plugging a jet. Drain the carb into a clear container, let set for a couple minutes and look for water on the bottom or other debris settling to bottom. Clean the air-filter is always a good maintains practice although in this situation I think its more of a fuel delivery problem (dirty jets) then an air restriction problem. A carb clean is probably your fix.

(Five Star, Bronze Certified Yamaha Tech.)

[jwriott]

Did the off/run/start button by any chance get wet? PW50's run exactly like you described when this happens. If so, pull the throttle assy off and dry out all the connectors. I've also had similar problems when the connections behind the number plate get wet. This is on a 1999 PW50.

[rkjaco]

PW 80 is a 2 smoke right? injected anyway. Different bike but I had a similar problem with a yz125 years ago. Let the gas sit in it to long and it would only run with the choke on. fixed the problem by unclogging the jet. We are talking a clog the size of a needle head will do this.

[dwillhauck22]

That happened to me on my XR80 The problem with it was the gas vent was not venting so the gas got stuck inside and I took the gas vent tube out and it had no problum running. I is the venting tubes I got me a pinhead!

Willhauck ?

[beer_studd_76]

Hey folks,

My son and I were riding this past weekend, and way out in the woods, his 02 PW 80 quit running. I changed the plug, and that did not help. It was cutting out and acting like a fouled plug. I finally found that turning the choke on, would get it cranked and run for a few minutes, then die again. We limped back to camp, I checked the flow of gas, which seems normal, but unsure of next step.....Thginking of draining gas, cleaning carb, one more new plug....after that no ideas.....any suggestions....

richen up the pilot circuit

[x440s_in_San_Diego]

Pilot jet is plugged with water or crud. Unscrew the pilot jet from the bottom of the carb, should be next to the main jet. This is longer and has holes drilled sideways and one up the middle. You should be able to see through all the holes including longways. If not, find needle or safety wire to poke through. This has happended to me several times. If the pilot is really small, the surface tension of water is enough to plug the hole with a drop of water.