Won't Run when warm :(

[TurboT]

Cool machine! It has a very Polaris'ish look to the front.

[SpudRider]

That is a very nice looking quad. Everyone loved the V4SW! I don't know why they discontinued this ATV; you were very lucky to get one!

Spud

[MICRider]

Cool looking machine, thank you for posting the pics . Love the front end, looks like it's ready for world domination! 8)

[Danthalis]

heh back to the drawing board. the slow death reared it's ugly head again. Runs fine for a minute, then slowly requires the choke to be closed, then it will run for about another minute with the choke completely closed, then nothing, have to let it sit for a few minutes.

Very uneasy about taking the carb apart, but getting closer and closer to it. Anyone else have an idea?

[MICRider]

Originally Posted by Danthalis

heh back to the drawing board. the slow death reared it's ugly head again. Runs fine for a minute, then slowly requires the choke to be closed, then it will run for about another minute with the choke completely closed, then nothing, have to let it sit for a few minutes.

Very uneasy about taking the carb apart, but getting closer and closer to it. Anyone else have an idea?

Is the gas cap vented on that model? Almost sounds like it is creating a vacuum in the fuel system. Perhaps the cap vent (if it has one) is plugged? If you take the cap off will it stay running? Shots in the dark on my part... Guessing either that or something with the float is wonky, maybe dirt in the seat?

[the_ripper]

Originally Posted by TurboT

Cool machine! It has a very Polaris'ish look to the front.

really? i was thinking more a kawasaki kfx.

[TurboT]

Most definetely Ripper you're on to something there. I don't see too many Kawa sport quads I think you pegged it.

[Danthalis]

Okay so I took the carb apart cleaned all the jets and needles, made sure the holes were open, cleared out the gas put in new gas with some sea foam to help break down anything that might be lingering.

Made sure the bowl stays full of gas, everything is connected, vented the gas cap. Still same problem, once it warms up it will stall out and sometimes if you close the choke you can get it to run a little longer then it dies and won't start back up for a few minutes.

Any ideas?

[FLASHLIGHTBOY]

If you have to have the choke on to make it run... and then it dies after awhile .. you may have a air leak at the spots where the carb & air inlet pipe attached to the engine block.. . when the engine is running with the choke closed... spray some ether around the carb gasket ..& the inlet pipe to the block... if it revs up.. or completly stalls out.. you have an air leak.. I have run into this many times.. and this is the problems for all the guys who say their motor will not start... BUT they have spark & etc.. believe me.. try it... as you have nothing to lose and you do not kno where to start.. this is a cheap way to see if you have an air inlet leak.. if it does this.. the pipe is warped.. file it flat.. check with a straight edge.. please post your results..

[Weldangrind]

Another possibility is that your idle jet is too small, and perhaps the clip is too high. You say that it will idle with the choke on, and that tells me that it needs more fuel.

If you again unscrew the top cap from the carb and lift out the slider, you can lower he clip to richen the mixture. Once you have the slider out, have a look at how the cable is routed through the slot in the slider and anchored at the bottom. The whole deal is held together by the pressure of the spring.

Squeeze the spring up against the cap with one hand, and slide the slider off of the cable with the other. Once the slider is out, you can remove the spring that is inside that secures the jet needle (the spring is likely a flat plate that is somewhat S shaped. Once the spring is out, the jet needle can be easily removed.

You'll notice that the jet needle has a circlip on it and five possible grooves. My guess is that the clip is currently in the top or second groove. I'd move it two spaces, reassemble and try again. Let us know if there was an improvement.

The idea is that if the clip is in the top groove of the needle, then the needle is nearly fully seated within the jet. If the clip is in the bottom groove of the needle, then the jet is nearly uncovered. This needle mates with the idle jet, and the idle jet is accessed from the bottom of the carb, but we'll go one step at a time for now.

My guess is that your Mikuni has a #20 idle jet, and you're trying to feed a 250cc engine with it. We'll figure it out.

[Danthalis]

Well the 2nd good cleaning and blow-out seems to have solved (or greatly reduced) the stalling out probelm. I can get it to start and run when warm.

Now after it's warmed up once you get past 1/2 throttle it bogs out and dies. Going to take the thing apart once more when it cools and make sure something hasn't come loose (or whatever the original problem was has just moved on to the next jet lol)

Also was in the process of attempting to adjust the air/fuel screw when this started to occur so that might be related too. On this bike it's extremely hard to adjust the air/fuel screw when warm because the exhaust pipe is literally right there and I keep burning the hell out of myself trying to get to it, might try fitting it with something that will make it more accessible provided I can think of something.


On a side note, before I took the engine out to fix a transmission problem, this engine and carb ran like a champ, never had a problem with it. Was after I put the thing back together that these problems started to surface. I never broke open the crank case or actual engine block though, so I highly doubt it's a compression or vacuum issue (at least I hope)

[Weldangrind]

Thanks for that detail. I'm leaning towards the air / fuel screw as the culprit. On my Beast, I use a screwdriver bit in a socket with a long 1/4" extension that just clears the ground. I pass the bit and extension up through the frame to the carb and I can adjust it easily. Try turning it all the way in carefully while counting the turns (that way you could return it to where it is now if necessary). Back it out two turns and start the engine. Rev the engine quickly and see if it stumbles. Trim the screw a 1/4 turn at a time until you find joy.

[TurboT]

Originally Posted by Weldangrind

Thanks for that detail. I'm leaning towards the air / fuel screw as the culprit. On my Beast, I use a screwdriver bit in a socket with a long 1/4" extension that just clears the ground. I pass the bit and extension up through the frame to the carb and I can adjust it easily. Try turning it all the way in carefully while counting the turns (that way you could return it to where it is now if necessary). Back it out two turns and start the engine. Rev the engine quickly and see if it stumbles. Trim the screw a 1/4 turn at a time until you find joy.

Or you can call Snap-On and get a 1.5 ft long carb screwdriver for a mere $100.. or, do what I did, and steal your dads. 8)

[Danthalis]

Well I had some mild success today. The main jet had come unscrewed :oops: :roll:

Got it back together, got it going and it kept going. Rev'd it up a bit let it idle, messed around with the fuel screw let it run for a good 20 minutes. Finally went for a ride around the block ran good up the gears. When I pulled the clutch it stalled out, but got it going right away. Did that twice second time around had to wait a second. By the time I got back to the garage had to close the choke to get it going limped in and shut it off. About a minute later turned on just fine.

So it improving quiet a bit, but still an issue kind of sounds like it's running out of gas in the bowl though? maybe I will replace that fuel line just to be safe and continue to f' around with the fuel screw.

[katoranger]

Do you have a fuel filter on there? It may not be flowing enough gas.

Allen