Hello,
I have an OS FL70 4 stroke engine, and I have a concern about it:
Recently I have been tuning it to get it running nicely. My fuel is S&W 15% 4 cycle with castor/synthetic blend. The propeller is a 12X7. After a lot of adjusting, the engine seems to be running well. But I'm a bit worried. My engine, when idling (at 2,100 RPM) makes a lot of visible smoke. When I raise the throttle, the smoke practically disappears! Here is a video of the problem:
[youtube]http://www.youtube.com/watch?v=Ofiy2Tl7J3I[/youtube]
This confuses me though. I set the engine normally. I was able to get the max RPM by adjusting the high speed needle and got to 9,400 RPM. I then richened the high speed needle so it ran at 9,200 RPM, which is about 3 clicks richer. Then, I set the low speed (air bleed screw) to the smoothest transition, and I was happy with about a 1 second transition. According to my process, the engine should be running slightlyrich,notlean!
Do you think I am running the engine too lean on the high speed?
I shouldn't be; considdering that richening it any more makes me lose a ton of performance and it makes the engine run inconsistently.

What do you all think?

Thanks
Mike

Sounds good to me. You should consider yourself lucky you even goy that FL to run!

It is not like tuning a car engine. Smoke at low speed is normal.

I tune 4 strokes to get a tiny touch of smoke even at high. Let the HS needle out a couple of clicks from full. Lubrication protects the engine.

Tom

The FL engine has an air bleed carb.  Thus the idle is controlled by the air bleed port or hole.  There is but one screw to open/close the hole.  Opening the hole leads to a leaner operation (more air less fuel mixture), closing the hole leads to a richer operation (more fuel and less air ratio).  Ideally, it should be set half way open (or half way closed - your choice of words).  Only a small variation from side to side can be achieved.  Alternatively, boring out the hole so that it is larger can also have an effect.  Juat set it for a good idle and leave it alone.

I would not worry about the smoke, probably a good sign in that oil is going through the combustion process.  The Castor in the blend will typically not repeat not be burned and thus results in visible smoke.

Sounds to me as if your engine is running just fine.

Chip

Thanks a ton, guys. I was really worried about running lean, this engine was not cheap and I'd rather not destroy it. Was using full synthetic previous to using this fuel so I'm not used to the different smoke properties. Again, thanks!<div>
</div><div>Mike</div>

Jet-

I'll almost bet when you put her up you will see a faint smoke trail reappear. Sounds like she running fine.