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OS FS-91 Surpass smoking at low rpm

Old 06-24-2007, 01:20 PM
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Default OS FS-91 Surpass smoking at low rpm

OS FS-91 Surpass (I) mounted in a 90 degree (right sideways) angle. Tank center line is slightly over carb center line as desired.

This OS FS-91 Surpass (I) develops a lot of smoke on the lower rpm. High speed needle is lean without major smoking. Looks like a rich idle needle setting. In fact, the low needle is turned in so far already that a little more right turn and the engine quits running. How can I adjust the low- and middle rpms? It is a Surpass I, and ran for years. Could it be the piston ring is worn out?
Old 06-25-2007, 09:52 AM
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Default RE: OS FS-91 Surpass smoking at low rpm

Smoking just means the mixture is rich. The engine is not like an automobile engine where you have oil in the pan, and smoking means that oil is getting into the combustion chamber. Because oil is already in the fuel, you'll get more smoke for richer mixtures, and more smoke if the fuel has oil that smokes more. If the engine's running well, we'd ignore it.
Old 06-25-2007, 05:41 PM
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Default RE: OS FS-91 Surpass smoking at low rpm

Mine smokes alot at idle to, its normal.
Old 07-07-2007, 08:46 AM
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Default RE: OS FS-91 Surpass smoking at low rpm

on the os 70 surpass the manual states that the direction that you screw the low end needle is the opposit of the high speed. You might be turning the wrong way and making it run ritch to the point that it quits. Just a thought.
Old 07-07-2007, 09:31 AM
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Default RE: OS FS-91 Surpass smoking at low rpm

Naval:

Thanks for your input. The FS-91 requires clockwise turns to lean the mixture. I have leaned the idle out as far as possible as well as the high speed. It takes good on the gas with no hesitation throtteling up or tendency to swallow on too much gas. High rpms are at about 10300 on a 12x8 APC. In the basement I have about 1900 rpms. It is still smoking but othervthan that it runs satisfactorily. Since this is a Surpass I (!) built in the early 90s, my guess is that the piston, piston ring, cylinder etc. is a little worn out by now.

PS: Bax is doing a great job here!

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