1987 Moto4 350 4x4 (possibly?) Requesting Help!!

[Baldwin]

I’m brand new to 4 wheelers and just bought a 1987 Yamaha Moto-4 350 4X4 to use for hunting. I say 1987, but not positive. The owner is not positive about the model year, but he said 1987 sounds about right. He also gave me his son's Clymer manual that covers 1987-1999. The frame has rusted just enough that the full serial number is no longer readable. I can read some numbers/letters, but it is spotty. Anyone know how to determine model and year if you cannot read the serial number? I have included photos.

So it started fine when I got it home, but it would only stay running if the choke was open even when warmed up. No identification numbers are stamped on my Mikuni carb to determine specific model. The choke is controlled by cable connection on dash, so it is not a model that has the choke lever right on side of carb. Since it would only start and run with choke open, I decided to rebuild the carb using the OEM rebuild kit. Took it apart, cleaned jets, orifices, replaced o-rings, gaskets, etc. After reinstalling the carb, the engine will still only run with choke open, but now the engine sounds like it wants to shut off and there is a consistent low volume backfire from the muffler. If I rev the engine, it sounds better, but still continues backfiring.

The fuel screw was seated at 2.5 full turns before I cleaned it so I put it back at that setting. 

I’ve looked high and low trying to find a video of someone rebuilding my specific carb, but it appears there are many variations. Appreciate any guidance to get it back to running like it should. I have included photos.

Any guidance on figuring out model year would be greatly appreciated.

Thanks for your time.  

[Gwbarm]

Im not really that familiar with that particular Mikuni, but it sounds like you are still clogged up somewhere. Did you take out the emulsion tube and clean it sludge getting in there is hard to clean out without pulling it. Most do have manual chokes via a thumb lever, make sure the plunger is working as it should, there is an adjustment for that.