I am attempting to get back into this hobby after life and kids have taken me away from it for a good 8-10 years. Exactly what is the purpose of the air bleed screw, what effect does it have on the engine and how is a correct adjustment made? The only thing I know for sure is that it has some effect on the idle - but then so does the low speed idle screw.Hi everybody. Now I told you that story so I could ask this question. I reinstalled the carb and lo & behold the engine ran much, much better - only had to adjust the main needle about 1/2 turn - maxed out at 11800 rpm with a 12圆 APC. When it came time to install the air bleed screw I was unsure of where to set it so I just screwed it in about half way. I think by doing it in that manner it automatically gets the needle in the ball park without the possiblity of damaging the carb seat when installing the assy. When installing the needle assy, I screwed the needle into the holder all the way then backed it off 2 1/2 turns - I then installed the holder (with needle) into the body. I removed all the the carb assessories and reinstalled them on the new carb body. Close comparison of the old and new needle seats does in fact verify that the old seat (the seat hole if you will) was much larger than the new one. Title changed to Surpass I, instead of Surpass II, by moderator to reflect the actual engineĪs you suggested, I replaced the carb body. :eek: This may be a stretch, but would improperly adjusted valves cause this problem? Thanks for your time. I don't think I left anything out that I checked but perhaps someone has had this problem and can provide this old timer with a clue. The needle itself shows no sign of being scored or marked like one would observe if it were turned closed too far. I did take that apart, checked everything, but nothing appears abnormal. The barrel assy appears to be working normally. I checked and tightened all engine screws, especially the carb screws. I ordered and replaced the needle valve and also the 'o' ring (thinking maybe there was an air leak) but nothing changed. At full throttle it comes close to proper adjustment but, as I said it just bottoms out. When attempting to get close to max RPM, the needle valve actually bottoms out. I bought the engine used and it runs and idles very well, with one exception.

I have an OS-70 Surpass with a needle valve problem.

Os 70 fs surpass