I have an older Saito 65, with an air bleed carb. It starts and idles fine, but when you take off, about 30 seconds into the flight, it dies. I'm getting a lot of practice with deadstick landings, but would rather not have this much practice. I have an OS F glow plug, using Cool Power 10 % fuel. I dont know if it has ever been properly maintained/adjusted, and don't know if that could be the problem.

David:

Check the valve clearances. A remote possibility is running hot from loss of breathing caused by loose valves.

That aside, does it hold its rpm when you run it up on the ground? If yes, check the tank mounting, the fuel may be foaming when it loses the stabilization of the wheels on the ground.

Is the engine cowled? You might be running hot due to poor air flow. Or the carb could be overpressured if there's not enough outlet air flow.

And all this supposes that you are running 200-300 on the rich side of peak rpm. You are, aren't you?

Bill.

Not cowled, on a Goldberg Tiger. Running rich, best guys at the field are tuning it. It holds idle on the ground, 2k without glow igniter. Will spin a 12x6 prop 10k, propped up to a 12x8 to drop the rpm's a little, to 8700.

So it holds idle. How long will it hold full throttle on the ground? That's a better test.

And in that installation a valve lash check is trivial. Do it.

And just for the Halibut, try a flight with the 12x6 prop. Might just be that little too much prop.

Bill.

On the ground, it will run at full throttle for as long as I want, but I don't hold it open for more than 20-30 seconds, I don't want to overheat it. You said valve lash check is trivial. What exactly do you mean? Not important?

David:

Trivial meaning very easy and fast to do.

Pull both rocker covers, and turn the engine into compression until you feet it go over the top. Back the prop until you are at the top, and hold it there for a moment, the compresion will leak down and it will stay in place. With the piston at TDC between the compression and power strokes you have it in position to check the valves.

Look at the attached pictures. In the first one, on the left you see the adjusting screw and lock nut. Grab the rocker at that end, check it for up and down free play. There should be just the least bit. If you feel more than the least bit of slop it is way too loose.

These pictures show me checking valve lash with a dial gauge, but most people use a feeler strip. Go to your local auto supply store and get a feeler set, but be sure it includes a 0.0015" thickness - many don't have one that thin.

Slide the 0.0015" feeler between the rocker and the valve stem, shown on the right in the picture, and adjust the screw to get a drag on the feeler as you slide it in and out. Try to make any error on the tight side, but up to 0.004" is OK according to the factory. The tighter you set the valves the better the engine will run, down to the point where the valve doesn't seal, of course. Using the dial gauge I set all my Saitos at 0.0005" clearance, and they all run great. Right. That's one half of one thousandth inch clearance.

No matter how tight you set the valves, so long as you have compression when the engine is cold it will run. As the engine heats the clearance opens due to metal expansion, you will never burn a valve in one of these engines, it's not to worry about. But with too much clearance you will accellerate cam and tappet wear, and hammer the valve seats. Tight is much better than loose.

For your first time you might want to see if another four stroke flier in your area will help you, but it's really an easy simple job.

Hope this helps.

Bill.

One thing to check is the inside of the fuel tank. If you have a pinhole in your line up near the neck, as the airplane flies the fuel moves to the rear of the tank. You now have the pinhole exposed to air and have an instant leaning of the engine. It took me quite a while to find the same problem. I changed the line inside the tank and no more problems. Another way to check for poor fuel draw is to hold the nose of the plane up for 20 to 30 seconds. If it runs OK with the nose up, than you can be sure that the problem is something else.

I checked the valve clearance last night. There was no gap initially, I then gapped it as per the instructions. I'm going to put in a new fuel tank and lines today, probably won't get a chance to fly for 3-4 days though. Thanks for all the help, I'll post when I test fly it.