I've got a buddy that has the Saito 91. The engine is pretty much still breaking in, it may have 3/4 of a gallon through it. The engine has run great right out of the box until about a week ago, it got to where it just would not run on the low end. Now I'm no rocket scientist, but I do no how to tune an engine. The valves have been adjusted. The engine is mounted on it's side, which should be no problem because I've got two 91's and a 100 mounted on their sides. The kicker of it all is that the engine runs flawlessly with the heat on the plug, but as soon as you take the glow starter off, the engine goes dead. As long as you have it at 1/4 throttle the engine runs fine, but pull it down below that and it goes dead. I've adjusted the low end like there is no tomorrow, but is is really hard to think you've done any good if the engine will not idle at all. Like I said, with the heat on, it actually runs better than mine. It will idle down to around 1800 RPM an run there all day long. The transition is superb and we tached it at around 9K. It will run like that on high end without the heat, just not on the low end. I personally put in an OS F plug, no help. He is running 15% nitro/20% oil which is ample nitro to achieve a smoothe idle. I told him that he may have to get an on-board glow to keep it running, but he didn't like the sound of that and said that he would just sell it if it came to that. It is his first four stroke, that I actually encouraged him to buy, but after the trouble this engine is putting him through, I doubt he ever buys another. It's got me stumped. Should he posssibly have to install an on-board glow to keep it running, and if so why? If it shouldn't be needed, what do we do to fix the problem.

Any advice would be greatly appreciated,

John

John,

Before you guys get too excited, did you try some of the fuel that you run in your Saito 91? The higher the nitro, the more prone a fuel is for picking up moisture. Contaminated fuel, if it's not too bad will run pretty good on top end but won't idle for toot. As it gets worse, its kinda ragged on the top end. It hard to get the needles set.

Enjoy,

Jim

I had same problem, I put in a new type "F" plug and fresh fuel [cool power 30%] ran fine. Good luck. Great motor!!!

soumds like the glow plug is bad. i run a mccoy plug and its been in there since it was new. its about two years old now.