Alternative Carbs - The Mikuni SBN

Mid last year I started toying with different carbs on the Sonerai. I dug through a bunch of dyno sheets of 2110cc engines with the same cam and heads in cars and found that they made about 25hp more than I was at 4000rpms. The only difference was the carb size. I spoke with a few people (like John from Aircooled.net) about the proper cam and compression ratio for my engine and they could not figure out why in the world I would run a single 34mm carb.

 I spent quite a while looking for a carb that was inexpensive and tunable both on the ground and in the air and found the SBN being discussed on a shifter cart website. Turns out that these guys also adjust their mixture during a race. It was used on performance watercraft before fuel injection became common.

After determining that the carb is going to work out by using my father in law's identical carb from his jet ski, I bought the one for the Sonerai today. Its a Mikuni Super BN Series 44mm Carburetor part number BN44-40-8067. It has a 44mm throat and a 40mm venturi.

Modifications for aircraft use are minimal:
- Remove the throttle return spring
- Install a normal throttle control arm
- Fabricate a throttle cable bracket
- Modify the high speed adjustable needle to accept a control arm and fabricate cable bracket

I am doing a couple of other things for my installation that would not have to be done
- Block off the onboard fuel pump. If I was not running a turbo I would have likely kept it as a backup and plumbed the pulse line to the intake manifold.
- Tap the fuel inlet and returns for 1/8" NPT so that AN fittings can be used.
- Added a bracket to hold the throttle position sensor

The carb with just about every possible needle and tuning jet cost me $204. A much nicer number than the other options available for our little engines! Tuning and tweaking will start this weekend. If anyone is interested, here is a link to the manual for the SBN series carbs: http://www.mikuni.com/pdf/sbn_manual.pdf