The engine is an O.S. .91FS. Valves just adjusted. New F plug (tried 2 of them) After starting it the glo starter is removed and almost instantly the engine dies. Fuel tank, lines, connections, all check out OK. Fuel is fresh. Idle needle set to match diagram in manual. Engine was in a serious crash recently. It has a fair number of hours on it, but the compression is very strong. The idle valve is out 6 full turns. Hi end needle valve out 2 1/2 turns. I will add that the rocker arms run smoothly and there is nothing to indicate damage of any kind from appearance or feel. Where would you suggest I go from here.?? Thank you for your interest....Rich

Sounds like an engine running to rich...Try backing the needle out about half a turn and see what happens. Just my opinion and I'm sure that people with A LOT more experieince will have much better suggestions (and some will probably say I'm crazy for even suggesting such an idea) but my suggestion is easy to test. It's late and the grey matter has just about shut down for the night but if I think of any other suggestions, I'll let you know. Good luck!

Mike

Your idle is way to rich, maybe.
Bill
http://www.bp55899.com

Could also be a bad gloplug. Very often, a new engine will have enough immediate wear to contaminate the plug so it no longer works properly.

I believe the low speed mixture is much too rich. SIX turns? That seems like a lot more than my old OS .70 when I fiddled with the idle needle. In fact, there was no "six turns out." The idle needle never bottomed out on mine, it just fell out into the carburetor!

The evidence is in the fact that the engine quits immediately when you pull the glow plug ignitor. If the idle mixture were too lean, it wouldn't quit until you tried to open the throttle. What's essentially happening here is that the excess fuel is splashing on the glow plug, putting out the fire. The battery keeps the plug lit, not the catalytic reaction between the combusting methanol and the platinum on the glow plug element.

Start by turning the low speed mixture in 1/4 of a turn at a time until the engine will run with the glow ignitor removed. From there, turn the low speed mixture in 1/8 of a turn at a time until the engine transitions smoothly.

I vote for mkirsch !!!!

I vote for mkirsch also. I had that very thing happen to me this weekend on a new saito 120. Ran good for about 3 tanks on the engine stand and was finiky at idle mounted 90 deg in a sukoi. It died imediately when I removed the glow driver. I dont remember which way I turned it but It got better after several times tweeking. I will also replace the stock plug with an OS-F.
Edwin

OK, got the message. Will try to lean this out as suggested above. I'll let you know, probably tomorrow, how it is doing. Many thanks for the responses!......Rich

Try a hotter glow plug as well.

A quick way of telling if the idle is too rich is to pinch the fuel line at idle. By reducing the fuel flow to the carb, if the idle is rich, it will speed up a little. If it speeds up a lot before quitting, then it's too rich. If it doesn't speed up before quitting, then it is too lean. Ideally, you want the idle to be slightly rich, so pinching the fuel line should speed idle up by just a little, maybe 200~300 rpm. This technique may be helpful when you need to find out when you need to stop fiddling w/ the idle screw.

OS is friendlier with imperfect adjustment. It will run and not quit even if the idle is like 1/2 turn too rich. Saito, on the other hand, you need to be withing 1/4 of a turn.