I have an 89 Big Bear which went from slightly hard to start to practically impossible and will not run. I took the carb apart and I believe I cleaned it pretty good, but this did not solve my problem. I moved on to the air filter and found the the entire case that the filter sits in was full of gas, right up to the air intake tube. I drained all this out and tried starting but just find that more gas is being pumped in.

Anybody know what could possibly be causing this?
I'm still hoping I can take care of this myself.

Thanks!
cweg

I just went out and messed with this some more. I didn't see any gas emptying into the air filter case any longer, but I have noticed that just by placing the top on the air filter case it cuts off enough air flow to make it stall. The air intake comes from up by the gas tank and there are no restrictions in it.
Is this just a simple adjustment that's needed? Choke problems?

Please help if you can!

 

My step dad had a old big bear that was doing the same thing. I found the boot that connects the carb to the motor had a split in it ( common problem on the yamha 350 motors). I replaced the boot ($50 from dealer) and it ran great and no more gas in the air box.

 

Thanks for the reply.
I do have this same problem, but it has been this way since I got it a year ago.
I have had it taped up pretty well and it has run fine for a year. Just a couple weeks ago did I start having problems.
Now it seems as though not enough air is getting to the carb.
No filter or cover on the air box, runs fine.
Just put the cover on and it stalls in 5 seconds tops.

cweg

 

Have you checked the intake valve clearance? Sounds like its too tight.

 

What would cause this clearance to decrease and suddenly become a problem?

 

On another note, do you transport this quad on its 4 wheels, or standing up on 2 wheels? That much fuel in the air box is typical when standing some quads up for a while. Since you say it continues to pump in when running, this is likely not the problem in your case.

 

Just normal engine operation, causes the valve clearance to change. If it tightens up, then the valve doesnt close all the way, and the symptoms are hard to start, and gas spitting out the intake....which sounds like what you have.

 

Is there a somewhat easy way to fix this?
Also, what about the fact that when I do not have the air filter or cover to the air case on, it seems to run fine. As soon as I put the cover on it seems as though it can't get air and stalls in a few seconds.

Thanks!
cweg

 

Depends on how mechanical you are, but doing the clearance check and adjustment is fairly easy. It takes longer to get access to the rockers than it does to do it.
How long since the air filter was cleaned and reoiled?

 

I have not cleaned or re-oiled the filter in the year that I had it.
What do you think about it running okay without the filter and cover on the air box?