Originally Posted by
Rcplanedan
That surely looks likecit runs fairly wel bert ..
but i an see its not truly running well of throttle there ..it seems a bit off. And yeah new engine..and i wathched your video of throttle mod.bad lighting but i understandwhat you were showing... .i got a pair of asp fs80 mufflers with my engine..well the exhaust is slapped together for its run tomorrow..il just use the fg arb ..i know i can get a tune with it..
The throttle mod works by changing the shape of the guide groove, then compensating the LS needle for it to bring idle back in range. the result is that Idle (after compensating the LS needle) remains the same, WOT remains the same because it is not affected by the grinding, but midrange gets leaner because of the shallower angle of the guide groove in the first half of the throttle stroke.
This mod works OK on the FT160, but you have to be a bit careful, it only needs a little bit of grinding (compared to singles).
I think that this is caused by uneven mixture distribution, and leaning out midrange too much will cause the leanest cylinder to drop.
Getting the distribution more even can be done in a similar way as what I did with my Radial (the tiny airholes) but I have the feeling that unlike the radial, on the FT160 this solution is very sensitive to dirt due to the location of the carburettor. I opted for a tiny "spoiler" in the intake instead.