Hello, I won an Ebay auction and in it among a lot of other stuff was a Balsa USA Bristol M1 monoplane. equipped with a Saito 91 four stroke. The engine looks to be well used so lets consider break in complete. I have fired the engine and had the needle at safe rich setting (filled the neighborhood street with smoke) just to lube and clean the thing out a bit. Now I have put a new glow plug in it and set forth to tuning. Have I mentioned I have never owned a four stoke before? Well I can't get the thing to idle low enough that it does not pull forward on me in the grass without it wanting to stall. It was still to slow to steer with the wire tail dragger set up (no rear wheel) so when I blipped the throttle to turn it darn near took off in front of my house. To much prop? (14X6) I also noticed it was a lot smoother running while the Glow igniter was still attached (Glow plug to cold?/any recommendations as I do not even know what plugs came with this thing.) Appreciate any help you pros can give me.

Mr67Stang

What goes up must come down... Wish it was when I was ready for it though.

For one thing, the .91 is a lot more than the M-1 needs, which will fly on a .46 2-stroke or a .56 4-stroke. Have you put a tach on the engine to see what you're turning at idle? Properly tuned, it can idle as low as 1900-2000 rpm, which is just ticking over. A 14-6 isn't too big, I have a 16-5 on my .91 / DR-1. The Bristol is a light plane, and the engine-prop combination is likely to pull it around even at idle. The tail skid isn't going to steer well without getting the tail light and using prop blast against the rudder to turn it, and like you said, it might want to take off, especially on pavement where there's no rolling resistance. I've flown a couple of the Bristols that my friends have, and am building one for myself. I'm putting an .80 on mine, and it will probably be too much, but it's an available engine. I am starting with a 14-4 prop and going from there.

What plug do you have in it? The stock Saito plug seems to keep the rpms the same when you take off the igniter, but I like the OS "F" plug for flying, even though my rpms drop slightly when I remove the igniter, indicating that it's a tiny bit colder than the Saito plug. I also use remote igniter sockets on several of my planes, and the clip seem to stay on the OS plug better. Either one is a good plug, pick one up and change it so you'll know what you have. Ken

Hello; I like what Ken says; OS "F" plug is the one I use on my Gee Bee with the Saito 91. There are low speed adjustment screw on the carberator. It is in the middle of the throttle lever. I would recommend that you adjust the low speed by using the pinch test; pinch the fuel line with the engine running, the engine should accelerate slightly before dying, this indicated a slightly rich idle setting to accomodate that extra burst of air when you open the throttle. If the engine just dies when you pinch the fuel line, you are too lean on the low speed and will have to back it out a bit and test again. I usually go one eighth of a turn at a time until it's just right. Like Ken says, the 91 is a pretty big engine to use with that plane, and on pavement it likely will creep forward on idle.

http://saito-engines.info/

This site has a lot of good info on Saito engines, as well as a link to the Saito homepage.