I recently purchased a used os 40fp and noticed when running it fuel seems to spit out of the base of the main needle. In other engines I have there are one or more rubber o-rings around the need which can be seen once the needle is removed from the carb. The carb in question is a 3A. Has anyone else got this carb/engine that can advise if the needle has an o-ring in it/on it as mine doesnt seem to have one fitted.

Adam.

This older series of OS needles which was the most common used on many different OS engines has no 'O' ring.

You may also want to note all FP's (which are very user friendly engines) utilise bleeder carbs for mid range and that horizontal screw in the front of the carb is the mid range adjustment. This screw intrudes into that visable bleed hole on the front of the carb.

What is important to remember is that this screw works exactly the opposite of the now common double needle type mid ranges. That is this screw is turned out to lean the mid range.

If your engine runs well then do not stress at what you may conceve as a leak.

John

Adam,

You could use high vacuum grease as a sealant for the threads of the needle if the adjustment is too loose.

http://osengines.com/parts/xr23381000.html

We'd just cut a short section of fuel tubing and slide it over the threads, the needle would bottom out against the tubing acting like an o-ring, just from the out side