The muffler on the Brodak engines is really pretty restrictive, and both the B-25 and the B-40 use the same muffler. I got a couple of the first run of the B-25 and was really disappointed in how it ran. It would needle fine, just no power, like it wouldn't pull the hat off your head. I posted about it here on Stunthanger, and maybe even on Stuka Stunt, and got a email from Tom Hampshire, whop asked me to send him the engine. After about a week, I got it back with the muffler modified to a straight through style, with a large-ish, short stinger. It was like a different engine!! I then thought that, well, if it helped the .25, I wonder how it will work on the B-40, and tried it on my Twister Shark and it then had an explosive break when the nose went up, but always came back to a 4 stroke in level flight. It really was incredible. Not wanting to get into another project trying to soften the break on the .40, I just put the stock exhaust back on. It sounds like you experienced something similar.
With the can on the muffler completely open, it will use a lot more fuel. To counter that it would need a smaller venturi. Take the long bolt and try grinding a slight bevel on the threaded end to see if you can clean up the threads and get the nut back on. If not, get a length of 2-56 all thread from the hobby shop and cut it to length and put a nut on both ends. You might want to solder the end that goes in front and that makes it more or less a bolt. If the all thread is a bit small, just put a flat washer Under the nuts, and maybe a dab of res silicone to seal the holes up.
Type at you later,
Dan McEntee
Topic: Half of muffler comes off B 40 (Read 137 times)