3 hp lightwin carb adjustment

[Canoe2]

Looking for some advice on a 1965 3 hp 2 cylinder light twin carb adjustment. There is only a single low speed adjustment, and i have set it at 1 and a half turns out, but the motor won't stay running unless i fiddle with the choke. Unless it is about halfway out, it won't run and periodically i have to pull it almost the whole way to prevent it from dying. Can't really set the carb properly until i can get it stay running....

I've re-done the carb kit (needle packing, high speed nozzle etc), blew out all the passages with carb cleaner, including pulling the core plug out. I've also been through the ignition system and replaced condensers etc. I really want to get this thing running so i can move it along to pay for getting its twin (i have two of these things, the other is in pieces on the garage floor) going.

Thanks in advance

 

[nwcove]

Re: 3 hp lightwin carb adjustment

sounds like its starving for fuel. try the needle at two turns out as you will find that 1.5 turns is just a baseline, and all carbs/motors have their own personality.

 

[Joe Reeves]

Re: 3 hp lightwin carb adjustment

If you're absolutely sure that the brass high speed jet is perfectly clean, check the in tank fuel filter... a stone like filter that is screwed into the gas tank with the gas line to the carburetor screwed into that. There may be a fuel restriction problem.

(Carburetor Adjustment - Single S/S Adjustable Needle Valve)
(J. Reeves)

Initial setting is: Slow speed = seat gently, then open 1-1/2 turns.

Start engine and set the rpms to where it just stays running. In segments of 1/8 turns, start to turn the S/S 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 (sounds like a mild backfire). 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 adjustment, 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.

 

[Canoe2]

Re: 3 hp lightwin carb adjustment

I thought about the fuel issue and ended up shortening the fuel line - it was a longer route than the original rotted one (i had it laying around and didn't shorten it before installing it) and i wondered if it might have slowed the fuel supply. Once i did that and set the s/s valve at 1.5 turns, it started up and stayed running while i fooled around with the valve. Now it cuts back and throttles up great. May even get it out for one rip before spring, thanks a lot!