OS 91FX

[Ihncheol Park]

Dave,

I ran 91SX-H with muffler, & tuned pipe.
The engine is nearly identical to 91FX except the porting & needle valve
which added 0.1 hp.  Bought it cheap from a heli guy.  91FX & 91SX-H were
both troublesome to many people.  Both use same piston & very slightly
different cylinder.

Only have rpm with tuned pipe. Added 1 extra headshim (gasket), Magnum #1,
APC 15x8 @ alittle above 10K, Not 100% tuned. Perry Vp-30.  I bought it to
use instead of YS 91. 91FX should do very similar.

Without a tuned pipe, 91FX will not overrun the YS 91AC/FZ.

Ihncheol Park

-----Original Message-----
From: discussion-request at nsrca.org
[mailto:discussion-request at nsrca.org]On Behalf Of David Gundling
Sent: Friday, October 24, 2003 9:44 AM
To: NSRCA discussion list
Subject: OS 91FX


What is the story on the 91FX. I have seen guys reporting
 that they are running up to 15 inch props. Reports of running
 a 14-10 are common. Is this with the muffler or is it obyained only with a
tuned pipe? The factory
recommended prop is something like a 13-8.On RC Universe there has
 been a love/hate situation with the engine. Some report no troubles.
Others can't get it to run well
despite numerous efforts and parts changes. Is this thing as strong as a
YS91?

Thanks.

Dave
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