Just did this swap today on a 79 Enticer 250. I used a brand new Mikuni 34mm, followed the advice on a 220 Main and 50 Pilot jet to replace the stock jets. I installed the single outlet mikuni fuel pump, and blocked off the oil injection line by simply putting a screw into the stock hose. I took the linkage rod right off the oil injector as well.
Here are some pointers and good info for anybody thinking about doing this.
Parts:
Mikuni VM34mm carb
Mikuni single outlet fuel pump
Universal throttle cable
Carb flange
1/4 inch fuel line/vacuum line
2-1/4 inch pod filter (or velocity stack if you are racing it i guess)
The carb flange center to center stud spacing is something like 2-1/4 inches. The closest I could come up with to match the 34mm carb was a 2-3/8 (VM34/200 was the mikuni number on mine). And something that nobody is mentioning on here is that after you slot the holes inward to make the flange fit... you lose your clearance to turn the 12mm nuts as you are tightening them. I decided to remove the studs and bolt the flange adapter from the flange side into the angled intake piece. This worked better because I used motion pro 8mm bolts with the smaller 10mm heads. Allen head 8mm bolts would work best.
The rest is pretty straight forward as far as installation. I didn't think the universal throttle cable was going to work... but it did. I think mine was an SPI cable. I also started out with the 220 main/50 pilot with a velocity stack that i picked up cheap cheap with the rest of the parts. It ran pretty good just like that and the plug had a good color to it. I pulled the carb off to check some things and it was obviously inhaling some random belt dust and goobers that old sleds accumulate. I decided to run a UNI pod filter after seeing that to keep any further junk out. At this point the sled would no longer run happily with the 50 pilot jet.... just way too rich with the pod filter vs. the stack. So the only jet I had to change it with was the 30 that the carb came with initially. Changed it and it ran good again... starts first pull every time.
I proceeded to plow through the 18 inches of fresh powder we just got with it for 10 minutes or so. Brought it in to check the plug and it had lightened up significantly. Like too light. Not white, but a light tan. So this is where I am at. I ordered some 35's and 40's to fiddle with. I think the 35 might be the ticket. Depending on what you are going to be doing with the sled, I think the 34mm carb is almost too big. Even with the jetting too lean or too rich, you have to keep it "on the pipe" to get any response out of it. This sled has 130PSI of compression too, so its not the engine that's holding it back. It was a fun project though, and that keihin carb can rot in hell.
-Adam
