Today I tried an APC 16x8 prop on the Ryobi. I turned both needles out 2 turns. I ran it full throttle and pealed the high speed needle. I then lowered the throttle to about 2000 rpm and peaked the low speed needle. This seemed to have little effect on how the engine ran other than determining how far I had to close the throttle to obtain an idle. Eventually it would prevent the engine from running. Long story short, I ended up with the low needle about 1 turn out and the high needle out about 1/4 turn. It simply would not lean out until it got to withing about 1/4 turn out. I thought the high speed needle was supposed to be about 1 1/8 turn out. What am I doing wrong? The engine ran well at these settings and I got a top rpm of about 7600. This still isn't as high as I thought that it would be given the size of the carb. I think it would do about the same with the stock carb. Of course, this is all assuming that my tach is accurate. The part that confuses me the most is the needle settings; they just don't seem right. What do you all think?

Brian

My G38 manual says HI speed to be set Zero to 1/4 turn out. What do you think of that! Capt,n

As the carb gets larger one might expect for the Hi needle to be leaner without other complimentary changes.

Bill

Guy's, Didn't mean to mislead anyone. During the break in the tach showed as high as 7900 rpms. The engine ran consistantly at 7600 with the MA 18x10. Maybe the tach is off but that is what it showed consistantly. I am using a GlowBee tach. Haven't had a chance to try the MA 20x8 wood Schimatar. I think the Big Bore Walbro gives the engine more grunt. I am not looking for high rpm's. I want thrust and it seems I am getting it. Time will tell. I'll post the results when I start fooling around with the engine again. Right now, I am thrashing to finish my model in time for the WRAM show.

Wouldnt hurt to check the calibration on that tach. Point it at a florescent light and see if its gives you 3600 rpm.
Edwin

I quit using my GloBee tach for just this reason; unreliable readings. New battery, even made a shield for the photocell, no matter. It would read different readings depending on how and where it was pointed. Too bad, because I like it's looks and functions other than the unreliable readings. I used to move it around and select the reading it gave out of the numerous it would give, that made the most sense. It would always read 3600 when pointed at a house light, as it should, but it still would give wildly varying readings on an airplane propellor.

I now use the TNC tach and it works great. I once checked it against a calibrated tach in a full size airplane, and it's reading was within one (1) rpm!!

I get about 7300 on an 18 x 6 APC prop with my Ryobi, and 7500 with a 16 x 8. I'm hoping it will do a little better with more run time, as it only has about 5 tanks of fuel through it...

A 20 x 8 prop is way too much prop for a Ryobi, unless it's on nitrous....

AV8TOR

Yeah! Same here. I returned mine to the LHS after working with it for two days. Got a H9 instead and been happy with that one.
Edwin