EW magneto drive gear

[RRinOz]

The roots of the teeth on my EW magneto drive gear are heavily marked and some of the teeth are worn to half their thickness. The cause seems to be that the gear is not positively located. The gear is bolted to the magneto drive flange and a bronze bush mounted on the timing chest wall is located between them. The assembly cannot be easily shimmed. Perhaps the magneto drive gear assembly should be fastened to a roller bearing rather than floating on a bush. Or perhaps the gear assembly should be more positively coupled to the magneto and thus rely on the magneto bearings. The end of the magneto carries a 2 winged nose that engages into 2 slots cut into the magneto drive flange at 90 degrees. This magneto nose piece has been heavily "got at" with a file so that it is very loose when mounted on the flange. This is engine number YE6885. How best to effect a repair? And can anyone suggest where I may obtain a new drive gear? Thanks in advance.

[Doug]

Sounds like you have the quick disconnect style magneto. The drive gear does not ride in a bronze bush, but rather in a hardened sleeve with a single row of 1/4 by 1/4 rollers held in a bronze cage. Water can get in here and rust out the races and rollers, making the fit (and alignment) very sloppy. Had there been an outrigger bearing in the timing chest cover, the gear alignment might have been more reliable. The housing/outer race in the timing chest and the inner race/stub shaft that the gear keys to are replaceable, but the parts are getting hard to source. So often it is a job for an engineering firm to make new parts to pattern.

Despite the convenience of the QD it must have been an ongoing problem with wear. Douglas got away from the design an went to a drive gear mounted directly on the magneto shaft taper. The magneto gained a flange that filled up and blocked off the hole in the rear of the timing chest.

-Doug