Tuning a Brison 3.2

[airriley]

I am looking for some help tuning a Brison 3.2. Has been a sweet engine since day 1, now in it's 3rd airframe, a WH 300.
From the first flight in this airframe it must have not liked something with the airflow. after a downline it would hesitete to pick back up. After a carb cleaning, removing the velocity stack, and running the pressure line into the fuse it is doing better, but not perfect. On a cold start it will die if you advance the throttle, you have to let it warm up a bit. The main issue is that at 1/4 to 1/2 throttle it sounds fat with the plane upright (engine inverted) when you go upside down it cleans up perfectly. Tried covering the hole in the side of the cowl, with no effect.
Anyone know how to verify if your mechanical spark advance is set properly?

Thanks for any help.

[obeid]

ihave brison 4.2 it raning good from 1999 so far so changing spark blag will help ithink tray it

[obeid]

ihave zdz100NG THE ENGINE RUNING GOOD IN QEQE SOMNZENE YAK 54 BUT THE PROBLEM IS OVER HEATING Idid pafaling from the cowel so it still runing hot about 305 F IN BOTHE CELENDES SO PLS HELP THANKS

[airriley]

Any other ideas besides getting a 4.2 or a zdz-100?

[Diablo]

To verify the mechanical throttle-coupled advance is set correctly, you must use a degree wheel and pointer. I use a popsicle stick in the exhaust port as a piston stop - rotate crank in both directions and note degrees. Halfway between is BDC. 180 degrees from BDC is TDC. When throttle is closed (idle), the spark should occur at 2-8 degrees BTDC. When throttle is wide open, spark should occur at 28 degrees BTDC. Full throttle advance timing should be adjusted first, then check to see where the idle timing is set. On a very old Brison (10 years), I had to reduce the throw by moving the linkage because it had way too much mechanical advance.