I purchase a 1997 yamaha 350 big bear a couple days ago. I test drove and ran strong, no leaks and looked pretty good. Yesterday i went to start it and noticed that i had to give it a little gas to get to start but then it just started to rev/idle high like if someone was holding the gas throttle. i tried pushing the gas throttle a little to see if it would idle normal but wouldn't. I turned it off and restarted it and rev/idle high again. after a couple of turn on and off's it started normal so i took for a spin and noticed that i would lose power while riding it and i would press the gas throttle but no response, then out of no where the power came back and go and come back agin. this would happen on both flat roads and hills. I am not a mechanic by any means but like to try to figure things out and if i can't i take to an atv mechanic.

so I would like to get some input on some things to check, i will be rebuilding/cleaning the carb but would like to know if their could be other possibilities that are causing the problems i mentioned.

Any help would be gratefully appreciated.

 

Anyone know where i can find a service manual?

 

There isn't much other than the carb that it could be. I would change the plug, just in case, then clean the carb out. Check that the choke mechanism is working properly, if stuck slightly open it gives a high idle.

 

Hey 2quiiker the Yamaha intake Boot on 350 big bears that connects Carb to the Head go bad and leak see if the Rubber is cracked or come loose.

 

I am not see any cracks or leaks. An ATV mechanic at my local shop told me that these ATVs u have to down shift after slowing down for dip, bump or turning a corner. True?
I have a 2001 Honda rancher 350 that unless I come to a complete stop or really slow down I don't have to down shift.

 

It probably would not hurt to change the fuel filter or add one if it does not have one.
Might try to run some c foam through it. Might need a carb kit.

 

Hey I hope you are down shifting when you slow down.If you try to take off in Third Gear you won't have much Power.

 

I do down shift based on how much i slow down. The big bear seems different.

 

yamaha carbs are junk. they are more than junk when the quad sits for long periods of time.

 

Sorry to butt in, but I'm really curious to know if there is an after market air intake boot for these carbs. OEM Suk. , really difficult to tighten them enough not to slip off. Again and again and....