Reply To: Caille 119(or 79, 88, 109) Carburetor Question

[PM T2]

The low speed screw controls AIR flow while the high speed controls FUEL.

The orifice you noted in the one plug is to allow air to flow into the idle circuit so if you have it in the low speed circuit, you’ve got it right. Turning the low speed screw in makes the mixture RICHER because its cutting off air flow.

The high speed needle works like most other needle valves inasmuch as turning it inward makes the fuel mixture leaner.

For initial settings, turn the low speed needle out 3/4 of a turn from close, and give the high speed on to one and a quarter turns out from closed. Use the choke to start the motor, but once the motor fires with the choke closed, open it right away before pulling on it again.

Best operation is on a boat. Running it in a barrel (if you’re doing that) presents problems with prop cavitation as well as cooling water flow. In a barrel they tend to pump water well when first started, but as the water gets churned up by t he prop, especially if ytou try running at higher engine speeds, the pump starts losing its bite and the water will eventually stop draining out of the exit pipe. Boat testing eliminates those issues.

Be aware of the fresh air supply when testing motors. I mean for the motor, not for you. I noticed I had outboards that didn’t want to run worth shit in the tank, and figured out it might be choking on its own exhaust. I didn’t have an exhaust fan on the tank so the smoke just hung around unless there was a stiff breeze blowing. Setting up a big pedestal fan near the tank cleared the air and the motors ran better. Hope this helps.

Best
PM T2

He's livin' in his own private Idaho..... I hope to go out quietly in my sleep, like my grand-dad did..... and not screaming, like the passengers in his car...