What would cause my fz91 to go dead rich after 20 or 30 seconds at idle? It runs great at midrange and above, and for a few seconds at idle, but then goes very rich and takes forever to clean up when the throttle is opened. I've set the idle as lean as posible (yes, I understand that the screw works oposite what we're used to) and turned the regulator in some, all to no avail.

I'm using Mach 7 15%, castor/synthetic blend, OS Type F plug, APC 14X8 or 14X10 prop.

It's been suggested that I need more nitro, or eliminate the castor, but this seems more like an adjustment or leakage problem to me since it runs so strong otherwise....

You might try the higher nitro percentage just to see. It might fix your problem.

Dave

Hi there,

I too have a fz91 and up till now it's been my fovorite engine. The idle problem just came out of nowhere. The thing ran great for my first flight on Tuesday morning and the second flight the engine didn't want to idle.

Have you fixed your problem?

Have you tried changing the glow plug?

Yes, the glow plug was the first thing I changed. and I'm using an OS type F I sent the motor to YS. They did a complete tune up on it. Runs great...