In my experience with the OS 160, I have found the main cause of them stopping in the air was the low speed needle set too rich. After low throttle and then advancing the power they would load up and stop.

Here is the way I have the tank setup. I made a dummy firewall and built the tank and throttle servo as a single unit to have easy access.

I may have a bigger problem than first suspected. I ran the engine at 1/3 tank as suggested, and it did run O.K. But after the engine warmed up I noticed at 1/4 to half throttle the engine made a horrible high pitched rasping noise, kind of like a very bad vibration. It would quit at WOT. I shut it down and it was smoking hot. After it cooled I decided to break it down and see what the problem may be. After disassembly I found the bearings are bad, the wrist pin was corroded and kept the connecting rod from moving freely, the piston is scored, and the pin in the piston that keeps the ring from moving was pushed all the way in. It appears that the previous owner set this engine up without using any after run oil and it corroded everything inside. I believe it is still repairable though.

WOW! Sorry to here about your engine .Could be a spendy little item by the time you get it running again .
If you don't mind my asking where did you pick the engine up at?

I saw it on RCU a few weeks ago and wound up trading a ready to fly Great Planes .40 size Ultimate. The person I got it from is from Beaumont TX. I am in no way slamming him about the engine. He stated up front that it was dead sticking and he lost his plane when it went through a barb wire fence. He was the second owner. After looking it over I think a set of bearings and some emory cloth on the wrist pin and crank should do the trick. Even though the piston is scored a bit ,the cylinder and ring are fine. I had a TT.46 PRO a while back with bascily the same problem and after a new set of bearings it was a great running engine.

Bummer ACAM37...

Once you get it back up and running you may find it will run perfectly with your setup as is...

Your tank doesn't look too aweful low (compared to for instance the GP CAP 232 stock location).
It's likely the bearings and other aspects of the engine were causing it to overheat... that alone may have been causing the issue, OR is was losing pressure at the high temps.

Mu suggestion after the engine is in flying order again is to put it back in as setup now... without cowl and fly it. This will give you quick and easy access to test temps and access needels until you have it where you want... OR the ability to add a pump if you end up needing to do so.

Sorry 'bout the luck... when you get her in the air she'll probably be a sweetie...

BTW... WHAT Bipoe airframe is that you're flying the 1.60 in? A recovered DP?

Maudib , actually the plane is a well used Direct connection that has been passed around the club. I acquired it last year and decided to strip it down and give it a makeover. Now the previous owners wish they still had it. From what I have read about this plane it is a .90 size, but this 1.60 is a perfect engine for this plane.It flies so good it's scary.

I believe you are right about the pump. It ran too good. It will run all day long on the ground with perfect transition. It is the easiest starting motor I have erver owned. All you have to do is bump the spinner and it cranks. The bearings are on order and everything else is cleaned up and ready for installation.

Update, Got the new bearings and installed them. The high pitch/knockning noise was still there. So I broke it back down. This time I found the rear bearing is spinning on the crankshaft. You can slip the bearing all the way on by hand and freely spin the inner race around the crank. I am pretty sure you should have to press it on. I need an expert opinion on this matter before I have to fork over money for a new crankshaft. I heard Locktite makes a product to fix this problem.

The inner race should not be able to spin on the crankshaft .Its a very small lite press size for size deal in most cases.
I wouldn't use any locktite inside of my engines the heat and oils will more than likely break it down and it would be a band aid so to speak at best,plus if any got into the bearing itself it would be ruined.

Depending on how hard the crankshaft is and how far undersize ,it may be able to be knurled back up and turned down to the proper size and reused. If your interested in this repair PM me

Other wise a new Crankshaft will be in order

Look,, I'm no expert and I don't claim to be. But,, I own a 160FX myself and have gone the green mile messing with all the after market fixes. Bisson muffler does not seem to produce as much tank pressure as the stock. TRUE. But in most cases who can run these giant stock mufflers on their planes ? (Without hacking everything to shreads.)
The point about rich low end and lean high speed needle settings makes good sense. I was deadsticking one day and tried the leaner low-end setting and did not flameout once. That was with a Perry VP30, stock muffler and 18x6W APC.

Again,,, no 2stroke guru here but I'll tell you what seemed to help me and maybe it will for you too.

Changed from the OS-8 and OS-F glow plug to the OS-A5. The A-5 instantly got rid of the mid range knocking and made for a smoother mid throttle flight.
Set the low-end by pinch test and transistion rate. Also you want it to back-flip easily so don't go too lean.
Set the high speed slightly rich to keep the engine cool. It will smoke alot but this seems to be the norm on the 160.
Now for the pump and extra junk. I tried all the pumps. Just makes the problems worse unless your wanting to set the tank on the CG. The larger fuel line theory is bunk too. I think one of the earlier posts from ? made the comment about too much fuel instead of not enough. I think that is the problem here because if it was a lack of fuel everyone would be deadsticking while at full throttle and most are not. It mainly happens at half throttle or while throttling back from full.

Cline Demand Regulator ! Ok,,, I know I woul;d read these posts about them and think,,, "Geez,, $60.00 ,, what else will they try to rip me for ?" But,,,, I inverted a Saito150 on a warbird recently. I must admit,,, they really work well.
Now with that in mind,,, does anyone here have an OS160FX with a cline and Bisson muffler that's still giving them trouble ?
I haven't ordered another Cline for my 160 yet. The big bore OS has totalled a large Edge 540T for me and almost did the same to a FW190 by deadsticking at the worst time. But if the Cline helps the 160 it might be worth looking into Acam37.

I posted the same question over in the OS tech support forum and BAX stated the rear bearing should in fact slide on by hand. I re-checked the bearing on the crank and if this is true then I am OK. There is no "slop" it fits real snug. I guess I will put it back together and run it. Thanks for everyones advice, as this engine has been a thorn in my side from day one. I guess once I can get the needles set right and do something with the exhaust pressure problem then it should be a fine engine.