I am having a hard time getting this thing to run right. It seems to be flooding itself and there is air bubbles between the pump and the carb. No bubbles between tank and pump either. Any Ideas, I have run lots of fuel through it and it is still unreliable?

I've heard it is very hard to tune engine. I have one New in the box, I am planning to exchange it.

Some O.S. Max FS-70 Ultimate engines have had pump/carb difficulties. Unfortunately, spare parts to correct those difficulties are not yet available from O.S. If the engine's sent here, and we can't get it set up, it would be exchanged.

Bax,

I am hearing a lot questionable things about the OS FS-70 Ultimate engine.

I purchased one of these in June and it never ran correctly. I sent it to Hobby Services who had it for over two months, because parts to replace the faulty pump or exchange engines were not available. Got a replacement engine back from Hobby Services last week. Did a bench test of the repalcement and I am finding it has the same flooding problems and unreliable WOT performace as the engine it replaced. Very unhappy with this engine and with OS service.

hello there this is my first time writting here. I come from Greece.
I have the following problem:
Beginning at middle throttle i see many bubbles coming from the pump to the carburetor and the engine isn/t getting faster and just quits. The bubbles are not coming from the tank system, as there are no bubbles in that line.
But I had ~20 flights and the engine was the best... At the 21 I had the problem during the flight.
From then the engine has not run again properly...
After half throtle i have the bubles and the engine quits..
I realy thinking go back to the two stroke os engines...
Everything in the engine is good... tank and fuel lines.. also 20% oil in the fuel.
Please realy we need your help if you know anything...
Thanks,Andrew Athanasoulas!

what section of the pump is giving most trouble?

the "pump part" mounted on the engines backplate? or the "pump part" that is built into the carb?