Today my normally good-running #W 100 engine suddenly began running erratically. It would slow down as if the throttle was being pulled back. I landed and on the ground it ran quite rough at most throttle settings. Actually it started and idled OK, but at higher throttles, it sounded rough. I thought it might be lean, so I richened the high speed needle and flew another flight. No better. next time I leaned the needle 1/2 turn so now I am a little leaner than the original. now the problem seems even a little worse.
The day is nearly over, so I just go on home. I find the ignition module has broken loose from its mount and is bouncing around inside the cowl. I had it screwed directly to the plywood that forms the top surface of the motor mount box. Could this explain the rough running? Do you normally soft mount this component? Mine broke off the mounting flange that is molded into the plastic case containing the electronics.

Its hard to say if the banging around is causing the problem, but I doubt it. I usually wrap the ignition module and secure much like an RX.

Most likely the ignition module is the trouble, possibly the plug boots. 3W had a batch of inferior plug boot insulators that failed prematurly.

Secure the module and run the engine and note if the problem is cured. If not check the plugs and inspect the engine for other possible problems. If you cannot find a contributing problem send the ignition in to Cactus Aviation or Aircraft International for service or replacement.

3W's also occasionally suffer from an air leak at the phenolic insulator between the engine block and carb. The block has been known to warp.

Good Luck.