RE: Reply to John
I had a chance to chat with Jim Gerard when I was trying to get my Moki 2.10 up to speed.
1)Nitro makes no difference, won't be 50 rpm difference between 0 nitro and 10% nitro. No reason at all to use it.
2)High volume pitts muffler is less restrictive, may effect the rpm by as much as 150-200rpm
3)Cutting the ends off makes a muffler less restrictive.
Thats the comments I got from Jim.
On my 2.10 I use the low volume muffler with the tips cut off, 0 nitro fuel. The Moki 20/10 Ultra prop,the Gold Standard, should hit 7500 rpm. Mine hit 7660.
I was where you are now. Low rpm and ready to ship it back. In fact I took the Moki off the Ultra Hots and gave it one more try, before it got boxed and shipped back. I knew it was a DUD so thats why I took it off the air frame. Well, surprise, when I put the Moki 20/10 prop on, and bench tested the motor it hit the exact rpm plus some.
Here is what I think is the rest of the story, so to speak. When I got the Moki, it was brand new and weak. It needed several break in runs. I did about 6 bench runs at 6000 rpm, sloppy rich. Then I put it on the Hots, might as well fly if the motor is running. I figured I would need perhaps another dozen or so flights, Well it never really got any better, No high rpm. Poor verticle with all props, Bambula being the best. When I finally gave up and called Jim I knew the motor was going back. He convinced me to give it a try with the Moki 20/10 prop. I had just bought it here on RCU but didn't have it yet. When I bench tested the prop, I used the same fuel tank from the Hots. But this time the RPM was there. I mean, first start, no adjustment to the needle valve.
My best guess is that I must have had a small kink in the fuel line. The Moki Ultra prop is light, very light, I don't know if that has any thing to do with it, I doubt it. If the Moki hits the mark with the Moki 20/10 prop, I think it will follow all the other posted numbers for prop rpm.
If your Moki is still weak, try a few no cost fixes. Cut the tips off the muffler, go to no nitro fuel, make sure the fuel line is the large tubbing all the way to the clunk, and that the clunk is drilled out.
I use a Cline. It's not needed, but I scratch build and put the tank on the CG. With the Cline I don't care where the tank is. Doesn't make a difference.
Hope this helps.
tonyc