Hello All. Bit of a newbie here. 6 months ago I bought a Yamaha 250 used and was told it was a Bear Tracker. Over the last few months of weekend riding it's become harder and harder to get it started so I figured it's probablly a carb problem. So I ordered a carb rebuild kit with what I was thinking was the correct year, make and model. When I get the carb kit I found it didn't match the carb that I have. So I found the model number (1P01-010) of the ATV near the gas tank under the seat and searching that number online I find a manual and find out it's a 05 Yamaha Bruin 250. Looking at the parts breakdown of the carb in the manual I can see the one in the picture doesn't match the one I have either. Everything else in the manual seems to match, just not the carb. So I start looking online and find an entire carb that matches what I have and is relatively cheap ($93 Ebay). The carb is from a 400 Big Bear and order it. Now I know that the motor on my ATV is a 250 but I order this carb anyway. Get it in and it's looks exactly the same. I install the brand new carb and I eventually got it started. When I push the throttle the motor revs until I pass about 1/3 throttle and then it starts to die out like it looses gas or something. I checked the throttle linkage and the thumb throttle is pulling the carb open all the way. Anyone have any ideas? Any help would be greatly appreciated. The carb was bought from Zoom Zoom Parts model number ZZP-KD783741. I didn't adjust anything on the new carb, I left it as it was

 

1st of all, there should be a serial # stamped into the frame, I think it's 16 digits, and on Yamahas that I have delt with, it's stamped on the left lower frame rail under the engine. This # will prove exactly what it is.

2nd of all, a 400cc motor is larger than a 250cc motor and naturally the 400 would want more fuel, so it's possible the carb is not the same. If the carb is the same, then the jets may be different, is so, you're in luck and just change the jets to the 250cc jets.

3rd of all, if an engine won't run above 1/3 throttle, then something is wrong with the main jet in the carb, usually it's stopped up. You'll have to remove the bowl on the bottom of the carb and take out the brass jets to clean them.

 

 

harder and harder to start? have you looked at valve adjustments? like Raptor450 stated, if it bogs down @ 1/3 throttle, it's starving for fuel. either you got a bad vacuum leak or the main jet is plugged/clogged, or your fuel filter is partially clogged/plugged. another item to check is the float/needle valve in case it's stuck and not allowing more fuel in there based on demand. while you got the carb apart, just go through it all. save yourself some headaches.

 

find the VIN, as stated on lower left frame rail. it's stamped/embossed there. 17 digit alphanumeric code. that'll tell us exactly what you got. look on base of fins on jug for cm3 displacement.

 

Thanks for the help guys. I really appreciate it. I haven't really had a chance to take apart the carb and check all the jets. But I noticed today that it runs fine (full throttle) if I take the air box cover off. Any ideas? Also, I searched everywhere on the frame, especially the left side frame by the wheel, and couldn't find a vin. I saw the diagram online showing exactly where it would be but it wasn't there.

 

I saw on the motor it's a 230cc

 

look under the seat and then look on the downtube from the handlebars.

 

as a matter of fact, please look on the left frame rail that starts to go vertical towards the downtube.

 

This could be an indication that your engine is running way too rich. Which could mean that your carb is too big or the jetting is too rich for your engine.