EDIT---------- save yourself some time and skip to the last post in this thread.

I've used OS engines since back when the first 35S hit the hobby shop counters. That's 50 years???? I've made engine parts and tried to hop 'em up with some success. I been there and done that a lot. And can usually solve about any engine problem at the field.

But I never bothered with 4cycles for myself. Got a bunch running for other guys, but never bought one for an airplane of mine.

So I figured it was time. I got a 46size Clipped Wing Cub that just cried out for a 4cycle. So I bought an OS70FL. I figured it'd be like the 6-7 OS46AXs I've broken in in the last 6-8 months (5 of 'em are mine). After all, the advertising said it had the same ABN and breakin proceedures.

Well, the instructions say to open the HS needle 2.5 turns etc etc. This one didn't and won't run unless that needle is about three quarters open from closed. The instructions say that you won't have to touch the settings. I assume they're talking about the airbleed. After believing what they said about that, I simply started trying to break the sucker in. When I finally got it to where I was trying to get it to idle, it stumbled every time the throttle was opened. So I did what everyone does. I did the pinch test and when it showed rich, I started opening up the airbleed screw. But before I did, I thought I'd turn it in to see where it was factory set. I didn't turn it in because when I looked, the tension screw was compressed. So I didn't bother. I figured it wouldn't turn in and if it did it'd just run into the spring. So I started turning the screw out a quarter turn at a time. It never changed the way it stumbled on throttle up. Yesterday, I figured all my turning would have finally opened the hole completely and decided I had to pull the engine out of the airplane so I could check some things.

I'd put the engine in the airplane like I've done with my last few 46AXs. Those suckers really are good enough to bypass bench breakin. But with the engine on the plane I couldn't check the airbleed to see if it was plugged.

With the engine out, I discovered the hole was as I suspected. wide open.... And I pressed fuel hose to it and blew and it sounded completely clear. I also did the blow test on the highspeed needle body. I pulled the hs-needle and blew again and no trash or anything came out. I'd replaced all the hoses at least twice. The two pressure fittings from the muffler had open holes that appeared to be flash free (no flash plugging the diameter holes that were drilled in them). The fittings were tight. The hoses from those fittings went to the right places, the small fitting to the backplate, the large to the tank.

My fuel tank will hold pressure overnight. No leaks. My fill/pressure pipe goes to the top of the tank. The pickup pipe has the clunk still connected and it's far enough away from the back so that it won't suck itself closed on the back wall. The clunk will move completely around in there. I've even swapped the lines and the engine won't pull from the vent, so it is working as a vent, and the muffler will blow bubbles out of the clunk so it's a working pickup. Got no reason to suspect the fuel system isn't perfect.

I checked the backplate for cracks and its screws. They're tight. The headbolts are good and tight. I don't have feeler gauges in the right sizes to check the valves, but they have paperthin at least gaps. The rocker cover was tight when I looked at the valve settings.

The thrust washer (prop hub) has freedom from the front bearing. However, there appears to be no windage in the crank. There is no forward-back "loosness" in the crank. But it's as free to rotate as any of the tightest 46AXs. Even if the crank was being slowed by the bearing fit, I can't see that as causing the engine to run the way it runs. The way it runs......

At about 3/4 opening on the hsneedle and any setting at all on the airbleed...... It will turn 9,200 on the ground and sound solid. A couple clicks toward lean on the needle and it stops dead. No backfiring, just stops. About 5-6 clicks out (richer) on the needle and it does what it's supposed to do, slows some. It'll take about a half turn in on the needle before it goes rough-rich. It is always weeping out of the venturi, no matter the needle setting, but not anything like excessively. There are always very small droplets of fuel spitting out of the venturi when it's running, but very very small ones and not many. I've not seen that with my couple of hundred 2cycles in the past, so assume that is simply what a 4cycle does between intake sucks. When the engine is tuned to turn 9200, that spitting is at it's least.

I'm flying the sucker on a Cub. I can't get a needle setting where the engine runs smoothly in the air. I fly a couple of laps and land and try another setting. It either runs with power and missing or it runs rich and missing. It will fly inverted the same. The max opening on the ground seems to be the same needle setting it'll take in the air. I expected it to take a couple clicks richer in the air than it'd do on the ground.

I've run through 3 glowplugs. Using OS-FS plugs. They all glow GOOD and have straight coils. I'd use every one of them again.

I'm using a balanced 13-6. I'm using good fuel and have tried a different fuel. I use 10% with 18% oil. It works great in another guys Magnum FS. There ain't no magic fuels. I use a filter on the fueling system and in the airplane between the tank and NV. It's tightly closed and has never had a speck in it yet, and you can believe me, I've checked that sucker more than once.

After discovering that I'd had the airbleed set every setting from closed to open I reset it last night to be 50% blocked by the screw. No change in the idle/throttle characteristics.

The engine will now idle slowly. It wouldn't until after about 10 tanks. After I discovered that it'd hold an idle, I decided to try and set the throttle-up because it would stumble rich on throttle-up. No matter the setting, the pinch test causes the engine to lean out when the tubing is pinched. Like I've mentioned, the last runs in the last few days had the airbleed screw set the full range at one time or another, either completely unblocked by the screw to 100% open.

The muffler is tight. The engine is tight on the mount and the mount is tight on the airplane.

It would seem that the factory suggested setting of 2.5 turns versus the actual setting of 3/4 should suggest something to an experienced engine guy. I'm experienced, but not with 4cycles. And truth is, this one isn't going to influence me into buying any more. Matter of fact, so far, this one sucks. I've suggested to the guys I'm always telling to buy OS, that this one must be a counterfeit.

Can't think of anything else to check or try................ any suggestions?