ORIGINAL: ram3500-RCU
ORIGINAL: OldFart1
Grettings from LAX
I've put a fresh Saito .72 in my Sig Mayhem 40 (fresh because the well worn Saito .72 was on my Buck Rogers when it encountered a ''localized gravity storm'')
I'm having an issue getting it to idle - as in it
won't below 2800-3000 RPM (and ''hunts'' at the lower end of that range). High speed needle wound up 1-3/4 turns out - pulls hard on a 12x6 APC. Playing with the low speed screw I can get great transition - but no low idle.
One thing that the guy who rebuilt the motor brought to my attention was my fuel. As all my other glow motors are YS - I run 30% Coolpower. The Saito ran great on this before - but as he pointed out the motor is a lot tighter now.
Also - what's the critical dimension from the spray bar centerline to the tank?
Thanks!
Sounds like it may be a low adjustment issue. Try backing the low needle out to flush with the plastic arm. Adjust the high end at this rich setting. Then start adjusting the low end for a good idle speed. The top end will need tweaked as well. I keep the supply line as short and as in line with the inlet as possible. I use 15% nitro in all my Saitos.
Truthfully I've never found the centerline from the tank to the carb or closeness to be an issue, and I've run tanks high, low, close and far away. I often curl lines around and always put filters in the fuel line. I used Wildcat in my Saitos before but have found the Powermaster YS/Saito 20/20 mix to be really, really good, much better in fact. What I HAVE found is a problem with fuel dots that have spring loaded valves in them. The Saitos suck air into the fuel line thru them, and it screws up the transition and sometimes the idle. I use the solid-plug type Hangar 9 (I think?) dot these days, it eliminates that as an issue.
That being said, this DOES NOT sound like an air leak. Air leaks in the fuel may screw up the high or low end, but they FOR SURE always screw up the transition, especially rapid transition. The engine asks for more fuel and sucks air bubbles instead. Yours has strong transition. A leak in the backplate could be possible, but it sounds like it's running too well otherwise, so I'd push that idea/possibility aside for now. See if somebody will lend you a tankfull of the 20/20 Powermaster to try out. This baby may simply be too tight to be running on that high of a nitro content, especially at idle. It might be heating up at idle due to the high nitro content. Heat and tight =tries to die on you.
I'm also in agreement with Ram3500 that you may simply need a new starting point for the idle mixture screw, and OUT is also what I'd say to start with. Out to the edge of the plastic might be a little far, but that's probably better than what you have now, richer seems to be what it wants. It told you this when it gave you great transition even though it has a poor idle. It wants a richer idle to start with. If not it would fall on its face when you transitioned. Instead, it LIKES the increase in fuel.
Remember, start by CAREFULLY screwing both needles in until they stop, counting the turns and the exact position they were in before you started playing with it.. That way, if everything else screws up, you can go right back to square one and no harm done by fooling around with it.
Then back out the idle mixture screw some and try working the high-end needle with that richer idle.
Good luck! Let us know how it's going.
Jim