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1954 Fastwin 15HP, how to set carb needles?

o2batsea

o2batsea

Outstanding Contributor
Well here's the thing. I have this old 15. actually it is pretty new all things considered. Anyway I want to be sure that I have the carb needles set up properly and I can't seem to find the setup procedure anywhere. There's a mixture needle and a high speed needle. Anyone have any insight? Do I just run them down all the way and back them out a couple turns or what?
 
Lower one is high speed mixture, upper one is idle speed mixture. Lower one should be open approx. 3/4 turn, upper one 1-1/2 turns. Final adjustment must be done on a boat, on the water. Adjust high speed while running wide open throttle to where it runs the best. Slow down to idle and do the same with upper one. Turn them in until it starts to falter, then back out till it smoothes out. Yes, it is that easy.
 
(Carburetor Adjustments - Two Adjustable N/Vs)
(J. Reeves)

Initial settings are: Bottom high speed = seat gently, then open 1 turn out. Top slow speed = seat gently, then open 1-1/2 turns.

Setting the high and low needle valves properly:

NOTE: For engines that DO NOT have a shift selection, obviously there is no NEUTRAL position. Simply lower the rpms to the lowest setting to obtain the low speed needle valve adjustment.

(High Speed) Start engine (it will run pretty rough), shift into forward gear, take up to full throttle. In segments of 1/8 turn, waiting for the engine to respond between turns, start turning in the bottom high speed needle valve. You'll reach a point whereas the engine will either start to die out or spit back (sounds like a mild backfire). At that point, back out the needle valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest setting.

(Low Speed) Slow the engine down to where it just stays running. Shift into neutral. Again in segments of 1/8 turns, start to turn the top needle valve in. Wait a few seconds for the engine to respond. As you turn the valve in, the rpms will increase. Lower the rpms again to where the engine will just stay running. Eventually you'll hit the point where the engine wants to die out or it will spit back. Again, at that point, back out the valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest slow speed setting.

When you have finished the above adjustments, you will have no reason to move them again unless the carburetor fouls/gums up from sitting, in which case you would be required to remove, clean, and rebuild the carburetor anyway.

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Thanks so much, that really helps. I have the repair manual and the owners manual and both of those say virtually nothing about the carb needles. Powerhead is zero time NOS, so I don't want to burn it up right off the bat.
 
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