Well I had recently posted up here about flooding this bike. And I fixed that with 5 oil changes. Then she was running fine. I then went riding the following weekend and it was on. Then about 3 hours into the ride it would idle and when given throttle, would die. I turned it over several times and let it idle for some time until it finally was able to get going. I then took it home and washed it, all the while being able to be driven. Then on the way to the garage same thing. Turn over then sputter off.
I then decided to look under the seat and found that the "throat" that goes from the air box to the carb was disconnected at the carb end. I am thinking when I was out riding I just happened to konw it back into place with some bumps on the road and just gave it enough seal to get the job done. But what I am thinking is that is may have gotten dirt or water in it while riding/cleaning. Have you had this problem before? I took the carb off and I am going to disassemble it today. I got a rebuild kit as well. I think maybe it just needs a nice cleaning. What do you think? Thanks guys!

 

It could have gotten dirt or water in the carb. Also when that boot comes off, the engine sucks more air in, which leans out the fuel mixture to make it run funny and hopefully your piston didn't get hot enough to mess anything up while it was running lean.

 

snaps man I really hope I didn't damage the piston.... Grrrr. Also, I bought this carb rebuild kit for it and there is one little screw with a needle nose that is not going into place anywhere. Do carb rebuild kits sometimes come with extra parts which may not be designated for your year carb. Like if this kit fits an 00-06 would it contain parts for all those years with some not being applicable to certain years? Thanks for the responses in advance. All help and info is appreciated.

 

is this for the big bear 250 or 400?

 

I Have THE Same Problem could you tell me how you fixed yours the fourwheeler runs fine and I cleaned the carb but after about half throttle it acts like rev limiter kicks in

ps if there is any way that you
could help it would be greatly
appreciated thank you fftopic :

 

It is a 400 buddy!

 

that screw may be the pilot screw that you are talking about.Does it have a spring,washer, and o ring on it or does it look like the picture in this link at all, http://www.rpmracingca.com/prodimage...lotScrew-1.jpg if so then its the pilot screw

 

oh btw it may not look exactly the same as the one above that is just a random pic of one but it should look similar

 

My Yamaha Prompt - Parts Catalog) this may help just put in your model and year then just look at the exploded view of the carburetor and the pilot screw is #7

 

Ok so I was able to put the carb back on it today and cranked it up.

1. It started, and was idling low at first, then got to kind of where it should after closing the choke a bit. I then gave it some gas and it would go back to a good idle which then began to drop. So I then closed the choke some and it began to idle high and stayed high.

2. Then I let it run still at a high idle to get warm. Depsite the high idle, even after opening the choke. I decided to pop it into gear and ride it. As soon as I put it in gear it just went on its own with no throttle.

3. I then was able to put the brake and it would stop, but then proceed once letting off the brakes.

It was tough changing gears as the throttle wouldn't let up. I then got it back to where I was working on it and then idled rather high. It continued to idle high and then would just making like a "puh" every now and then, which would come from the air box intake. Then brrrrrrr and "puh", puh" and then brrrrr and then I eventually turned it off. So with the choke all the way open it wouldn't slow the idle.

I am kind of confused and frustrated as it all went back to gether rather well and its not right... GRRRr haha.

I am thinking it has to do with the throttle screw set. The number 39 in this diagram:

http://www.yamahapartshouse.com/oemp...2cf/carburetor

I twisted it a few times when I had the carb off the bike (not intentionally). I was reading up online and I heard something like screw it in (clockwise) all the way until it stops, don't tighten too much. Then unscrew it counter clockwise 2 1/2 turns. Have yall heard of this? I went ahead and did that and got it to turn over but then it just puttered out after a hot second. Am I going in the right direction with this? I am going to upload the vid I made so you can see what I am talking about. Thanks for alll the help guys. I think I almost got it, just need a little more help...

Here is the video: