Attn: Sno Jet guys 433 carb help needed

[_FIII]

I have had it with the Walbro carb on my 71 Super Jet. I have had it apart well over a dozen times and I can't figure out what is wrong. I was going to sell the sled but now I am keeping it. It has the Yammi 433 fan cooled twin for a mill. My query is: what size mikuni carb would do well on this machine and does any one have a baseline for jetting specs. I found this place but it doesn't list Yamaha or Snow-Jet.

http://www.bayshorecad.com/Sleds/Literature/Carbs/MikuniVM/Mik_Conversion_Specs.pdf

Very good chart but doesn't help me with this sled. I also will apologize to Walbro fans for my lack of patience with these carbs.

 

[Ding]

Don't know which Walbro carb you have on there. Looking at some old info (I can't trust my memory anymore), Sno Jet used the SS433 in a '71 model called the 71YSS. Yamaha used twin Keihin 406's on that motor, but Sno-Jet used twin Tillotson HR's. These 2 carbs were very similar in size and application. The next year Keihin changed ID numbers to the more common CD, and CDX line. However, both of these were a twin carb setup.

In '72 Sno Jet used the S433 motor with a single Tillotson HD.

These are all diaphragm pump carbs. The Walbro is a nice carb, but I like the Keihin carbs better. They just seem to be less finicky. A Keihin CD42-38 with both mixture screws at 1 1/4 turns out is good starting point. Tuning this setup should be as easy as turning a couple screws.

However, I am guessing that you want to go with an external Fuel Pump, and a non-diaphragm carb. Obviously the Mikuni round slides are a good opotion for this, but you will have to do the calculations for jetting and then tune from there. You also have to do more conversion for carb adapter and linkage setup.

I am also guessing that you may have a transplanted engine or at least the carb. Can you tell us more about what you have?