I am running my first LA 46. It is on a Brodak p40 64 ft lines. I have been through all the engine set up threads. Tried venturies from .257-.281 Stock nva and st nva. 11x4 up to 12.25x3.75 . OS #8 plug and 1.5 v fox long rc miracle. Sig 10-10-10. 4oz brodak standard wedge. Running in a solid 2 the problem is it runs away about 1/2 way through. Does not matter if running pressure or not. My last set-up, No pressure, .057 os ventury, st nva, stock 3030 muffler, 12.25x3.75 apc, miracle plug. Set just below peak. Still runs away. Changed fuel to some that I added an extra 5% castor to and what a difference! Has my problem been lack of castor the whole time? Now at total content of 25% of which 15% castor. 5 plus mins on 2.5 oz, 64ft center to center about 5.1 seconds. I am getting close.

Set just below peak.

That might be the problem, Rick. I'm running mine so that when the plane's held vertical, it's just still rich of peak. Back in the horizontal position, it's much richer (still 2-stroke) and RPM drops a couple hundred.
Mine's a factory C/L engine so it's a 7mm venturi, OS NVA, GMA 10-22, APC 11.5 X 4 or 12.25 X 3.75.

The small venture I don't believe is hurting me. I have plenty of power and speed. I have not tried fattening up the needle since I added more oil so I may be able to do that now. I do like the 5+ minutes on 2 1/2 of fuel should be over 8 minutes on four oz. I hope the weather cooperates this weekend I would really like to get this worked out.

  I wouldn't be too proud of the fuel economy. Fuel consumption does two things, makes power and provides cooling. If you ain't burning fuel, you ain't doing either. My ST.51s used close to four ounces for the pattern, a bit more in cooler weather, I don't have much experience with the LA.46 but would think something in the four ounce range for the pattern would be in the ball park.
  Type at you later,
   Dan McEntee

Yup, burn more fuel! Many use 4.5+ oz in .46 LA's at normal altitudes. Adding more oil will also require more fuel load, as it happens. The engine needs to be rich enough to not go lean in the overheads at the end of the run, and I suspect you're launching too lean. Using a tachometer? You should. I would wonder how much running time your engine has? Maybe not enough? Most seem to run well from #1, but fuel load still needs to be decreased after 30-40 flights. Where's yours fit in this realm? Or is it one of those rare ones that needs more running?

Remember that the muffler outlet has a similar effect to a venturi change. See Randy's pinned articles at the top of the Engine Forum. Either bigger venturi or bigger muffler outlet will improve the pumping efficiency. Have you put a rubber ducky on the muffler? Big or small one? More prop load burns more fuel but increases heat, too. Another thought...you're running a fuel filter between tank and NV? A big one? I'm not a fan of those tiny ones...too much chance for them to clog after very few flights to suit me.   Steve

And to date I only have about 1 hour on this engine.

I am running a crap trap fuel filter. and the stock muffler. Rubber ducky? Do you mean the dubro rubber exhaust deflector? If so no. I am flying the beginner pattern so I do not need the full tank. That is why I was only running 2 1/2 oz. I do not think that I am over lean but I do not have a reliable tach. Could I go richer? yes But I have not had the chance to try it yet to see if it runs away. Since I am running more oil it may stay consistant. I would like to get it in a rich two just off of a four. If it does I may need to go to a larger venture to get the rpm back up.

Ah, knowing it's the Beginner's Pattern makes the fuel load sound a lot more reasonable. But I'd go with the stock venturi and use a layer or two of pantyhose mesh over it to effectively reduce the venturi size...and keep "the stuff" out. That's another reason to use muffler pressure...keeps the micro bugs and micro seeds out of the fuel tank and thus, filter. Plus, it prevents rich/lean when going up/downwind. Yes, there are other fixes for this, but muffler pressure isn't a bad thing.

Try some different props. The 11.5 x 4 APC works well for me, and locally, Tim and Tom use the 11 x 4.5 Thunder Tiger Cyclone. I still say to change the tank to uniflow, add muffler pressure, and launch richer. If it sags overhead, it's clearly too lean. Try doing 2 OH8's instead of the WO and see if it goes lean. I'd suggest getting a tachometer (Hanger 9 Mini-Tach, $28) and use it to set the rpm before every flight...and I mean, EVERY flight. 

Have you read the "sticky" topics at the top of this engine forum about OS .46LA setups? Randy Smith's articles? Some good stuff in that lot.  Steve

I ran it this weekend at Polk City and it did pretty well. I launch around 8600 rpm with the .257 ven. and super tigre nva. It goes over lean around 9250rpm. This is with the 12.25x3.75 apc. plenty of power and plenty fast. Now that I have a little time before Muncie I will try the middle venture. Also the 11.5x4 apc.