When I'm tuning motor I can get it running quite well but it dies when I remove glow starter even at high rpm. I have a os61fs and I recently installed a new glow plug. Any ideas? Thanks!

Sounds way too rich

I hate to answer a question with a question. Does it spit fuel when it is running out of the exhaust or make a lot of smoke or both.

It could even be the wrong plug. That engine runs well on an #3 or #8 plug

An engine that is tuned properly and runs great with the glow driver on then dies when removed means the plug is not doing its job. If it is remotely close to being tuned correctly will still run if the plug is good. What kind of glow driver are you using?? What condition is the plug when you look at the coils and when the driver is hooked up to it out of the engine?? One other idea, what fuel are you running and have you run it before?? [8D]

In the original post, you mentioned the "OS .61fs." Is this the 4-stroke? Or did you mis-type and mean FX or SF? It makes a difference on the type plug you use.

No its a 4 stroke! Thanks for the other tips now Ive got running better but need to tune the air bleed screw. Any tips?

Prop size for this engine should be something like a 13-6 or 14-6, the heavier, the better. Master Airscrew or APC come to mind.

Remember, this procedure is based on your engine having an air bleed screw, not a low speed mixture screw. Same basic principles, different applications.

Air bleed adjusts air into carb at idle. Low spped mixture screw regulates fuel into carb at idle.

First set the high speed needle for a "full RPM minus a few hundred" speed.

With the engine running at as low an idle you can get, and the glow plug battery connected, do the "pinch test".

Pinch the fuel tube from the tank to the carb tightly and listen to the engine. If it speeds up, it's too rich. Open the air bleed screw a bit and try again.

if it immediately slows and dies, it's too lean. Close the air bleed a bit and try again.

Once the approximate setting is found, try letting the engine sit at idle with no glow battery for several minutes. Then briskly open the throttle. The engine should increase speed with no spitting or sputtering. If it coughs and blows a lot of smoke, it's still too rich. Open the air bleed a tiny bit.

If it hesitates and sags, it's too lean. Close the air bleed a tiny bit.

A good idle speed for this engine would be in the 2000 - 2200 RPM range, all day long.

You have an old OS .61FS ? Cool, I have one of them as well. Quite old, and not nearly as powerful as "modern" 4-strokes, but still great engines.

I run an APC 13x6 on mine. I've tried up to a 14x8, but that was a bit too much. I've also run as small as a 12x6, but I think that it was a bit too small for the engine.

Anyway, you want an OS "F" plug in that engine. If you're using a 2-stroke plug, it will do what you describe. This engine is a second generation 4-stroke, so it acts just a little different from the current stuff.

Btw, use a tach. Mine really doesn't want to run over 10k rpm, I usually set for about 9.5k with the APC 13x6, and get great runs. I suspect it gets in to valve float at about 11k rpm, so if you are taching around 10 on the ground, and the prop unloads in the air, you wind up with funky performance.

Oh, I run open stack, no muffler on mine. It's actually pretty quiet sounding, even with no muffler. (actually, it's loud on the ground, but the low pitch makes it not "feel" bad, and in the air, it seems real quiet).

I run Omega 10% or 15% fuel with no problems.

Thanks everyone for your help!
It's great to know that lots of people are willing to help out beginers.
Cheers!

Oh, I forgot to mention, check the valve lash. You should have a feeler gage to check the clearances. While I wouldn't expect that to cause the engine to quit when the plug lighter is removed, it can't hurt to check the clearances once in a while anyway.