Is muffler pressure needed on an OS .70 Surpass? I obtained one from a friend that used a flex pipe that promptly cracked after a few flights. I want to fly with this but wonder if the engine will lean out too much without muffler pressure. I've run the engine with a straight pipe on the ground and tehre doesn't seem to be any problems.Thereseems to be little if any difference in sound without the muffler attatched to the flex pipe.

bhady</p>

The OS 70 Surpass II came standard with a muffler including the nipple to presurize the tank. I'd have to go to attic and dig out my original box and instructions to see if it specified "needing" tank pressure. Perhaps someone with the instructions a bit more handy will beat me to the answer.

If the tank is properly mounted and close to the engine you might get away without using pressure from the muffler set up.  Or you can add a Perry oscillating pump and that will do the trick for sure.  </p>

Cheers,</p>

Chip</p>