i have a rossi 40 on my Q500, its have a venturi 9mm on it and nelson pipe. i can't turn the engine scharp, y can't set it on point? whats the probleme please?

Hi!
Do you use:
9x6, 9x7 , 9x6,5 APC prop or a 8" - 8,75" APC pylonracing prop?
0-5% nitro?
Rossi 6 glow plug?
5-6oz Trettra "Bubbleless" tank?

...You should!

hi, i use APC 8,75X7 0% nitro , rossi 4 en tettra bubbless tank
when i use yhe nelson pipe it wont turn scharp,its te fast lean.
i make the exhause on the sleeve 1mm bigger higher
the orginal pipe from rossi it turn better
sorry for my bad englisch i am from belgium

Do you drain the air out of the bladder tank, before putting fuel in it?

yes,

Check it for leaks then.

yes, had the same problem in my nelson powered Polecat- slight leak at the mouth of the bladder- replaced the bladder and no further troubles. regards trevor h[:-]

no leaks, its a pipe problem,

Check your pressure nipple on the Nelson pipe. Make sure it's not blocked and you're getting muffler pressure to your tank...

Sounds like your not getting enough back pressure then.

i think that i make the exhause on the sleeve to big

Quote - "i think that i make the exhause on the sleeve to big"

Yes, I would agree, 1 mm would be just shy of .040" and that is a lot on an engine that already has pretty high port timings. You can put a degree wheel on it but I bet the exhaust timing is going to be greater than 185 deg. and that is high. May be time for a new sleeve/piston if it has been cut too far. [8D]

Good luck getting it figured out.

Well... you can't just start cutting up a sleeve like that and expect good results. The minimum you could have done was at least put a degree wheel on it to see what the stock timing was, and start working from there... in SMALL increases. If you just "eyeball" 1mm, you know nothing.

And if you're trying to make a Nelson out of a Rossi that way, you're in for a disappointment. There's a lot more to performance than exhaust timing.

Have you actually measured what rpm you are turning? Exactly what Nelson muffler are you using? If your engine has a hard time reaching the muffler's tuned rpm range, you will get tuning problems like you have now. You will be turning in that needle to get it staged on the pipe, but since the engine can't get there, you're starving it to death. This may well be the case if you are using the Q500 muffler. If you are, you may get better result from the Nelson" "sport" muffler.

Bring your engine along to the field next weekend, so we can have a look at it. (unless you don't want us looking ) I'll bring my degree wheel along, so we can at least have a look at that exhaust timing.

I know, I know... a little late. The race was last week, but there's always next time.