Mikuni Carb Identification

[smokem]

Hi there, I have a 94 Big Bear 350 i got through trade. The P.O. said it would need a valve job soon as it smoked on start up and only ran at full choke. I brought it home and discovered the intake manifold was split in half and wrapped in duct tape. I got a new manifold from ZoomZoom and when i started it, it ran on half choke but backfired through the carb blowing up the new intake manifold. I pulled the carb to give it a full clean and realized the piston valve assembly in the carb is different than the one in the service manual. The one in the service manual is held in place under the cap with a spring and upper and lower connector, whereas the carb i have has the piston valve attached to an arm that connects through the throttle linkage shaft. I searched the number off the carb 3HN 00 H421 but came up empty. When i looked at pics of a warrior carb the piston valve assembly seem more alike. Can anyone tell me if it is the factory carb? Also on a side note. I checked the cam timing and it seems off a tooth or so, probably causing the back fire?

[oxidized_black]

i thought the big bears had the mukuni vm or bm series carbs, maybe yours did get switched. i would take the pictures and email them to mukuni to verify what yamaha it came off of ...

[smokem]

Well i can't find any contact info for Mikuni on there website. I tried the local Yamaha dealer and they said they have no way of identifying the carb. I did send an email to CPW who is a Mikuni distributer. I measured and the carb is 32mm. On a side note if the timings off a tooth would it back fire through the carb? Because it looks like it off a tooth. Im going to reset the timing, clean the carb and tape up the intake boot and try this again.

[oxidized_black]

i would think if its off a tooth, it would do some crazy stuff.

Mikuni American Corporation

8910 Mikuni Avenue

Northridge, CA 91324-3496

Tel: (818) 885-1242

Fax: (818) 993-6877

maybe fax these guys ???

MikuniPower.com - Mikuni Distributors

[smokem]

i would think if its off a tooth, it would do some crazy stuff.

It did. It blew apart a brand new intake manifold. I belive the rotation on these motors is counter clock wise? If thats the case according to the cam timing mark its look a few degrees off at TDC. Which mean the intake valve wouldnt be fully closed at TDC causing ignition of the fuel being fed from the carb. I tried calling Mikuni and there closed till like the 4th and i dont have access to a fax machine. Does any one know the what the ignition timing should be off hand? I belive it should line up with the F mark?

[smokem]

Well by searching ebay i found an identecal carb listed as a YAMAHA KODIAK 400 BIG BEAR 350 MOTO 4 Carb. Quoting the seller This is a VERY nice like new example of the OEM 32mm single cable Mikuni BTM that will fit all 80's and early/mid 90's models of the YAMAHA BIG BEAR and MOTO 4 350, KODIAK 400. So it look like i have the right carb.

[smokem]

It did. It blew apart a brand new intake manifold. I belive the rotation on these motors is counter clock wise? If thats the case according to the cam timing mark its look a few degrees off at TDC. Which mean the intake valve wouldnt be fully closed at TDC causing ignition of the fuel being fed from the carb. I tried calling Mikuni and there closed till like the 4th and i dont have access to a fax machine. Does any one know the what the ignition timing should be off hand? I belive it should line up with the F mark?

Well i dont know what i was thinking here earlier. Timing is checked at top of compression stroke and the valves close at the begaining of the compression stroke so the valve is not open as i was thinking earlier. If that was the case there wouldnt be any compression, right? As far as the timing marks, i discoverd the tensioner was max out so looks like i will need a new chain soon.