Hello guys, new member here and needing some technical help from someone more experienced then me. I am trying to help a friend out with his 1998 Timberwolf 250 2wd. This thing will not idle without the choke. My first thought was either vacuum leak or dirty pilot jet. Ruled out the vacuum leak so I tore the carb apart and rebuilt it. New factory spec jets and verified all passages were clear.
Reinstalled carb and same problem. Further diagnosis found that if I block off the choke port on the front of the carb (the side that faces the air cleaner) it will actually idle fairly well. The o-ring on the choke plunger was replaced but I did notice that even with the choke off I could blow air into the front port and air would escape out the rear port. So this is the first problem.
Second problem. Leaving the front choke port plugged up and the engine idling fine if you rev the engine up and release the throttle the rpm's will skyrocket and never lower. You have to kill the ignition, but can restart it and idle speed is normal again. After stabing the throttle I can see the throttle plunger returning back to it's closed position, all while the rpm's keep increasing.
I have spent several hours fighting these problems, even removed the carb and went through it one more time to double check myself. I am begining to think the carb is worn out but at the same time doubt that is the problem. Any suggestions or test anybody wants to recomend I am all ears.
Truly sorry for the long newbie post, I am trying to be as specific as possible without confusing you all. With that said I must say one more thing. While replacing a leaking crankcase to cylinder block gasket I noticed it has a .5mm oversize piston. Could this oversize be enough to require larger carb jetting? Again, if you managed to stay awake through this post I appreciate you all taking the time to read it and appreciate all the help.

Steve

 

Well, tried a few things and made some progress. Did the math and realized that the overbore should not require a jet change. What I did do is plug the air inlet at the front of the carb (air filter side) and this solved my idle problems. The engine starts right up and I could actually get the idle speed and pilot jet adjusted. Took her for a ride and everything is ok, but still having the run away rpm problems. At idle everything is fine but if you stab the throttle the rpm's just continue to climb even though the throttle slider valve is returned to idle. So my theory on this is that either the slider valve is worn, the bore in the carb for the valve is worn or both. I am thinking it may be time to just replace the whole carb. Anyone have any suggestions?

 

Ok, I'm just going to type for a bit. This may or may not help you. I have said this many, many times in the past. The ONLY way an engine can RPM is with an air leak.

That being said, I had much the same problem with my daughters Breeze. I would start it with the choke on and the RPM would climb. I checked everything for air leaks and did not find anything.

I finally checked the choke and found it was binding in the bore. What I did not know was the choke had an air bleed port on the back side of the carb on the right side. This is where the engine was getting its air.

I actually had to put some sand paper on a drill rod and flap the bore until it was clean. Then I cleaned the plunger up and put everything back together and it is all good now.

Make darn sure the choke is very free in it bore so it can move and will cover and uncover the air bleed.

Anyway, that's my story, hope it helps.

 

Were is you needle jet e-clip postion at? the inital setting should be middle groove[should be 3rd groove from top]. the idle should have an crisp fall no feather like fall.So IMO i would move e-clip down one at an time[which raises needle jet] which will give more fuel in that curcuit...But if you think you have an air leak then take wd40 and spray intake manifold and carb mounts and if engine loads up an goes dead than bingo there the leak,but i no change then lean fuel mixture in that curcuit or throttle cable or slide is sticking..Good Luck.

 

Thanks for the reply Doctorturbo. I did verify that the choke is not binding in the bore. One thing that I did notice though is that with the o-ring on the choke plunger is actually above the air inlet and outlet ports in the choke bore and this is when the plunger is fully seated down in the bore. I am starting to think that this may not be the correct plunger for this carb. Not sure how to best describe it, but I see nothing other than the choke plunger body itself to seal the ports when the choke is not being used. The problem with that though is that the plunger has to be smaller than the bore so it can slide up and down without binding. Does this make any sense? I will go to the dealer and maybe they have a choke in stock that I can compare to what I have now.

 

papa hogg scoot, according to the manual the jet needle clip should be on the 4th groove from the top and that is where I set mine. I use carb cleaner or propane to find air leaks and using both techniques I have not found any vacuum leaks. Luckily the air intake on these machines is very simple and I checked and triple checked the inlet boot for cracks and the inlet manifold o-rings are new.
I also verified that the throttle slide is not sticking. When the engine is running and the air filter tube is off, you can stab the throttle, watch the slide rise then fall back to idle position but the engine rpm's will increase to very high levels and I have to kill the engine. Restart it and it idles fine for as long as you care to let it idle. Have you ever seen the slides or bore in the carb wear out? The slide in this carb looks like the piston skirts of a well worn engine.

 

Well Steve, My bet is still on the choke. If you can see the slide seat then I trust you. Sounds like you did your homework bytrying to find the vacuume leak also.

That leaves that choke and the air port that it uncovers.

Do this. When it is ideling real high, put your finger over the air port on the back of the carb and see what happens.

 

When you say to cover the air port on the back of the carb, are you talking about the engine side or air filter side of the carb? I currently have the choke air port on the air filter side of the carb covered.

 

On my daughters Breeze it has a small port (1/4" or so?) on the carb air horn. This is where it picks up air when the choke (enrichener) is on. That is why the RPM climbs on the engine when the choke is on. It sort of works like a fast idle when the the engine is cold.

 

Yep, that is the one I have pluged. I found a local man that has a spare t-wolf carb and he gave me the choke plunger from it. I am going to give it a try and will let you all know the outcome. Thanks again.