Hello All,
I have a saito .72 mounted inverted on a on a Aresti Arf.
I put a sullivan tank in. The center line of the tank is pretty close to the center of the spray bar. I have an OS "f" type plug installed. The engine was broken in with about a gallon of 15%fuel.
The engine runs at full throttle. When I bring it down to about 1/4
throttle, the engines RPM's will start to "pulse" or become erratic.
When I was braking in the engine it did not seem to have the problem.(The engine was up right). Is there something special I need to do if the engine is inverted?
Would the low idle adjustment cause this? I did try to lean and richen it out, but the same thing. Anyone has any suggestions?
This is the first 4 stroke Ive owned and its not a pleasent experience.
Please help!
Thanks

Will it idle with the glow heat still on, if it will, lean the low end a little, it should speed up, then reduce the speed with the throttle, It may take two or three small leaning adjustments to get it right. Each time you adjust remove the glow power and see what you have. Turn the idle screw about 1/16 to 1/8 of a turn at a time.

No longer support RCU

I am about convinced that Saito got a bad batch of carburetor o-rings. Had the same problem with a new Saito 100. Removed the idle o-ring and it was nicked. Replaced it with an OS o-ring I had and things got better. Then I examined the hi-speed needle o-ring. The needle valve doesn't even touch it, whereas it should be a tight sliding fit to seal the hi-speed needle from leaking air. I'm guessing that when I get it replaced that the pulsing will go away. Anyone know the dimensions or specifications for the METRIC o-rings that Saito uses in their carbs?

Roger Hill

I went back to the low idle screw and found that it was turned all the way in, as if it was completly close. I have no idea how it got that way? This would mean it is way to lean? It really didnt matter if the glow was on or off. When the engine was at full throttle it would run fine. When I brought it down to 1/4 throttle it would "pulse" which I still don't understand way that happens, and at idle it would just die. Which now I know its the low end adjustment. mpj220 recalls about a full turn out, saitos web site says the screw should be about flush with the throttle arm. Which was a good place to start. Does this sound close or does someone have a better place to start. Thanks for all your help!
Keith

No longer support RCU

Thanks a lot for the help Mark!
I will try that. I am just debating if I should stay in the warm house or go out in the cold and try this?
Keith

No longer support RCU

Hey Mark,
You are 100% correct. I am going to wait a few more hours.
My FieldBox battery is still charging. I ran it dead yesterday trying to get this to run right.
Thanks

Hey skyfox: I have a Saito 91 that was acting similar to yours. The instructions called for the low end needle to be 1 millimeter away from the spray-bar. keep in mind I live at 6000' altitude, but this was wayyyyyyy rich I wen't flush with the throttle arm setting, as was suggested by someone here, and what a difference. I have since turned an additional 1/8 turn to lean and it purrrrrrrrrrrs like a kitten. I also adjusted the valves just for s**ts and giggles and the thing is almost spooky now it makes so much power. Both valves were loose by several thousandths from the factory. As was the low end needle. Happy flying: Garry

hello garry,
Thanks for the info.
I did get it running pretty good. The low idle screw was turned all the way in, which was way too lean. I turned it out, its not quite flush with the throttle arm, but it is about 1mm in.
Thanks,
Keith

Hey Keith: Always glad to help. I suggest checking the valves as well. Mine ran fine out of the box pretty much except the minor surging, which a low needle adjustment took care of, but when I adjusted the valves it came alive. Saito provides a feeler gage so I had to tinker, this has bitten me before but in this case it woke up my engine. Happy flying Garry

Break in suggests you run the valves down after the first 30 min of run time. I have a 72 on a Ultra Stick. After the break in on 15%, I adjusted the low end needle valve and ran the valves down. It takes the Ultra Stick straight up with a 12x8 prop and 20% nitro. Its a house of power!

They say that moving the idle valve flush to the throttle arm will make it pretty rich, anyone know howmany turns in, aprox, befor you get pretty lean?