YS91 Mixture setting for FAI

[Zilly]

With my stratus now flying the FAI head I tried cranking down the head RPM to about 1400 RPM and was very impressed with how stable the model felt I can see why you guys are doing your hover manouvers at this head speed, however my YS91 was not quite so impressed as it was really out of its comfort zone with and 8.18 ratio we are talking engine RPMs of 11,500.

Does anyone here use a mixture servo? I guess its the middle needle on the YS that needs to leaned out ? I realise that my engine is no the YS version wit the remote needle however I cant see whay I dont just fix an extension to the middle needle on the carb and slap on a servo :lol:

I am sure someoe may have something to say on the matter.

IS the YS 91ST4-R differnce just a change in the length of the needle so a servo can be connected or is there more to it?

z

[DavidH]

Never ran an ST-R, the regular 91 ST would sit and purr at 1400-1450 rpm on the head in a hover. Check the marks on the carb barrel, make sure your hovering with the barrel open to the 40% mark on the carb. This will be the mark that is nearly in the middle of its range. If your hovering with the barrel open around 50%, then the mixture is trying to operate from two slots on the barrel. I never had to run an onboard mixture control with the ST series of YS engines.

David