Vintage Dirt Bike Q & A

Ok, dumb question for the day (or maybe 3). Seems snowmobiles use Mikuni carbs (and other brands) that to me look just like motorcycle carbs. Difference is the motorcycle carbs are for gravity feed application where the snowmobiles evidently have a fuel pump. And now the question. Can a snowmobile carb be modifed for gravity feed? What is the difference between the two types? Maybe the float valve? Any insight would be appreciated. Great site! Thanks ...Van

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1980 Honda CR125R

Shouldn't be any difference as far as fuel feed goes. Floats should handle fuel pump or gravity just fine.

Rick

That's what I was thinking but I saw some Mikuni VM30S thru VM34S carbs on a site that specifically said they would not work for gravity feed application. I guess the "S" stands for Snowmobile. The price was good even if I had to buy jets to tune for my bike. Wonder what they meant by would not work? ...Van

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1980 Honda CR125R

I did some research and it appears the difference between the fuel pump/pulse type Mikuni and the gravity type is the size of the needle and seat. Looks like to convert to gravity feed would just require changing the needle and seat to a larger size. And of course experimenting with pilot and main jet. Anyone out there ever converted a snowmobile carb to gravity feed? Thanks I never seem to do things the easy way .....Van

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1980 Honda CR125R