1988 Yamaha bigbear 350 boggs down with no power

[Pinoyredneck]

Hi everyone,

I was on this site about 15 years ago but forgot my original login. Now I am Happy to be back again.

I have a 1988 yamaha bigbear 350 4x4. It was running fine, then all of a sudden, my exhaust would glow red hot and would loose power. It will idle no problem, but as soon as you roll the power on, there isnt much there.

I have verified the following to be within specs.

- compression is good (according to a good friend)
- leak down is very acceptable.(according to a good friend)
- timing is right on. (According to a good friend and I have verified myself)
- cleaned air filter

Here is what I have replaced so far:

- carburator intake boot
- carburator (chinese carb off amazon)
- spark plug

* I still have the original Mikuni carburator, but I had to drill out the low speed air screw as it was jammed solid in the housing. I have not purchased a carb rebuild kit for it yet, but it is an option I am willing to try. Just keep in mind that the problem started even before I changed the carburator.

What I have noticed:

Multiple sparks during complete cycle ( much more than just 1 spark per cycle)

What I have also tried:

- removed all of the handlebar and thumb warmer electrical that were installed by previous owner.
- baked the CDI In the oven.

I have recently purchased another CDI off a 1987 bigbear and waiting for it to arrive.
If this doesnt solve the problem, I will replace the coil and/or stator/pulse generator next.

I dont know what else the issue could be.

Has anyone ever had this problem before?

Please help!

Thank you,

Paul

[dustrunner]

Sounds like a carb issue to me. i have had a few of those models and never had a problem.... those aftermarket carbs imo. are junk.

[shortline10]

Make sure your exhaust is flowing freely .