mikehoulder

Thtee questions:
Part 22826131 Throttle Stop Screw. What is its function and how does it work? I thought that I could use this screw to lock the carb rotor to keep it open 1/32" following David Gierke's advice on setting the air-bleed screw. But it doesn't seem to do anything at all.

The needle valve thumb screw has me puzzled as well. I find that its closed position does not remain fixed but gradually migrates anticlockwise. Tightening the set screw doesn't seem to have an effect. And certainly I can't rotate the thumb screw with the needle closed to its original position.

And what is the purpose of the needle valve ratchet spring?

Sorry to ask dumb questions, but your answers will be a great help.
Many many thanks
Mike

Bax

My Feedback: (11)

The throttle stop screw allows you to set the limit when you retard the throttle to idle. You have a "hard" stop for the idle setting.

The high-speed needle will change the "closed" position if it actually gets tightened instead of closed. That's because the taper of the needle will start to enlarge the needle seat. There isn't a set screw for the high-speed needle valve, unless you're talking about a small screw inside the end, which is used to retain a wire when you need an extension to the needle valve.

The ratchet spring keeps the high-speed needle from changing position when the engine is running. Vibration can cause it to move if the spring wasnt' present.

mikehoulder

Thanks very much, Bill.

So I need a very much more gentle touch when I close the needle valve. Evidently the ratchet spring looks after itself. With the small set screw, now the memory returns. I came across an explanation of its use some time ago; but couldn't find it again.

Sorry, I haven't grasped the function of the throttle stop screw. What I would like it to do is stop the carb rotor from closing completely when the throttle lever is pulled back to its stop. It may actually do this. But if it does, I don't know how to accomplish it. Tightening or loosening the stop screw does not appear to have any effect on the carb rotor when the throttle lever is pulled back.

Best wishes
Mike

Bax

My Feedback: (11)

OK, I gave a general answer. The O.S. Max .65 LA only has a screw that retains the carb barrel. You adjust the travel of the throttle via your servo linkage geometry and/or the transmitter's end point adjustment.