Os 46

[elev8]

I am almost finished with a Goldberg ARF Cub and it has an OS 46 MAX. I had it running today but I couldn't seem to keep it running for more than a few miunutes. It seems to be ventilated good enough, I think it just needs some fine-tuning. I know now that the needle valve adjusts air-fuel mixture and that setting it richer can help cool it off, but I am wondering how the carbuerator adjustment works. Is that for air intake adjustment also?

[pirate281]

Elev8:

I think there are better threads for this question on this forum; this thread is for "builders workshop" and I think you should look in the "engines" thread under aircraft-fuel-general.

But to get you started, the main needle valve is for the mid to high range of the throttle (where the carb bore is open 1/4 of the way to full open) and the other needle is for the idle, where the carb bore is open less than 1/4 (approx). Some engines have an air bleed for the idle which works the opposite of a needle valve in that it affects the air intake as opposed to the fuel intake. On an air bleed, as you turn the screw in, you restrict the air flow in thus making the the mixture richer. But since you mentioned an OS 46 MAX, you shouldn't have an idle air bleed adjustment but rather a second needle valve.

A good general starting point on these engines is to adjust the high end first by turning the high end to fully shut, then opening it two complete turns. From here you can get a better engine run and then turn it in a little at a time until it is at the proper setting. Then adjust the low end needle (at idle).

The other thing you need to keep in mind is if this is a cowled model, you must allow enough airflow for the engine intake as well as cooling. This almost sounds like a cooling problem- sounds like the engine runs for a few minutes but then overheats and stops. Make sure you have flow-through on your cowl (the air has to be able to flow over the engine and out the back of the cowl.

Sorry if I went into more detail than needed, hope this helps.

Jeff

[elev8]

Thanks for all the info and sorry for the late reply. You have been very helpful, the advice you gave me has been put to use. :)