I recently bought a RTF H9 33% Cap with a 3W 85B2 with smoke mufflers in it. I don’t know the engine’s history as far as run time, but it appeared to be broken in, at least. I will most likely be selling it as I’d like a more power and less weight up front. This is only my 2nd gasser (DA50, prior) and I wanted to get a little feedback on it.

So far I’ve got about 2 gallons of Amsoil 50:1 ran through it. It’s consistently turning an NX 26x10 at 5900RPM. It idles well, transitions quickly. I have found the carb needles to be very sensitive compared to the DA. It doesn’t like to be run rich in the low to midrange at all. I’ve also found that if it’s slightly rich in the low to midrange, it goes VERY rich in knife edge. With the low to midrange properly leaned it doesn’t run any differently in any attitude. It does have the carb diaphragm line run into the fuse. The engine has monster compression so I’m wondering if I should use 93 octane? I’m currently running 87 as that’s what my DA was most happy on. I’m also considering a 26x8 prop to get the revs up a little for more thrust. It has the blue dot ignition; I’m guessing this is the older version that requires lower voltage? I’m currently running a 2 cell 2800Mah Li Ion with the reg set to 5.2 volts.
Any feedback would be greatly appreciated.

The 3w 85 is a very smooth motor and runs great. 3w's dont need to be run sloppy rich. They are designed to be tuned for perfect low, mid, and top end smoothness. To set your low end run it on the ground and lean out the low end untill the engine cant take a full power jam of the throttle stick. Then back off the low end by 1/16-1/8th of a turn and try that. You can run any gas you would like in the engine. I run chevron supreme with techron and have always like that fuel. The blue dot ignition is the newer style of the old ignition. You can run up to 6 volts on this ignition without a problem. Running a higher voltage will not increase your power though so your setup is fine.
Garrett Morrison

Thanks for the info, Garret. When tuned properly, it is indeed very smooth throughout the powerband. Now if I could just keep it tuned.. It tends to richen up a little about halfway through a flight. I think the needle(s) might be moving a little from the vibration due to being extended by the original owner (see pic). Once I get them set, i'll try securing them with a zip tie or rubber tubing. I think I might try 93 octane this weekend and see how it likes it; my DA preferred 87 exclusively.

Does 5900RPM sound right for a 26x10?

That's about right for a 26X10, leave it on there. As you get more time on it, it will gain some RPM's. And get rid of those needle extensions, they are rubbing on the muffler, and like you said, more than likely moving. And I use the same gas as Garrett

Tom