I've done some looking and reading threads and have noticed that no one is running Mikuini or keihin carburetors. cv vs fixed venturi carburetors. Has anyone tried the fixed over the variable venturi?

 

Quote:

Originally Posted by twist

I've done some looking and reading threads and have noticed that no one is running Mikuini or keihin carburetors. cv vs fixed venturi carburetors. Has anyone tried the fixed over the variable venturi?

In 5 plus years here on this forum I have seen ONE set of FCR carbs for sale..... ,, not even sure they were ever installed between sales..

the carbs used on this bike are the LARGEST carbs Honda every installed on a bike.... Suitable swaps are just not common.

If you’re a machinist by trade and a motorcycle tinker by choice.. you could make something work at a cost that was worth while.

 

Aren't the factory carbs a Keihin design?

 

OEM carbs are indeed Keihins. As for non-CV carbs, FCR 41s are apparently a fairly common mod in Japan, where kits are available in both TPS and non-TPS equipped versions. They are, however, quite $$$$$$ to get over on this side of the Pacific.....

 

Yes i mis typed..

Point was the same.. I was not making it about the brand, just the size and style

 

Without a STG2 engine it is hard to justify the cost involved.

CV carbs not only adjust for altitude changes but also changes in the weather.

So on a "Street VTR", even with engine mods, CVs are the way to go on this bike.

Track only, that is a different story.

 

after more reading it makes sense to not have a fixed venturi carburetor unless it's on a racing motor and even then it has to be adjusted for track conditions and weather etc. Besides, having a carburetor with TPS makes perfect sense and there just is no need or advantage for the fixed venturi. For an older engine that has been modified flat slide FV carbs are awesome. The CV carbs I've got the most exerience with are Bing's and they are not known for their snappy acceleration and throttle response. But, they deal with changing conditions beautifully. I've been dealing with old bikes for a long time and I now have to come up to speed with modern engines and components. I thought this would be a gas it and ride bike with very little that can be done to it. I can see now I will be into the engine and making improvements and minor modifications. Don't want to race, just have a bike that runs GREAT and is fun to ride.

 

CV carbs work great for a street application due to their adaptability as mentioned. However the standard carbs you are thinking of are not fixed venturi. They are variable venturi just like CV carbs. Just what opens the slides is different. These use a vacuum diaphragm where a standard carb the cable attached to the throttle directly opens them.

A fixed venturi carb is like what you find on older carbureted cars. They have a fixed bore with just a butterfly valve to control the flow. The design works great at WOT but lacks efficiency everywhere else when compared to a variable venturi.

 

I stand corrected.

 

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https://www.superhawkforum.com/forum...-issues-31331/