Starter and flywheel ring gear question (photo)

[Brian Vickers]

Kelly Aerospace MZ-4222 starter; I mounted the starter that came with my engine core and noticed the gear is resting on the flywheel. See photo. This doesn't seem right(?). Isn't an aircraft starter the same as a car? The gear is only engaged when the starter is activated? The starter is in very nice condition and looks almost new.

Also, while turning the flywheel I noticed the ring gear slips. In fact, I can wiggle it off. I don't see a mechanical fastener. Is this supposed to by a tight press fit?

[David-aviator]

Originally Posted by Brian Vickers

Kelly Aerospace MZ-4222 starter; I mounted the starter that came with my engine core and noticed the gear is resting on the flywheel. See photo. This doesn't seem right(?). Isn't an aircraft starter the same as a car? The gear is only engaged when the starter is activated? The starter is in very nice condition and looks almost new.

Also, while turning the flywheel I noticed the ring gear slips. In fact, I can wiggle it off. I don't see a mechanical fastener. Is this supposed to by a tight press fit?

The ring gear very definitely is a press fit. It probably is the wrong ring gear for that fly wheel. They do not slide on and off unless the parts are heated and frozen appropriately. I can't remember which is which but I've done it and when temps return to normal, the ring gear is attached very tight.

Info on the starter for your particular engine can be found at
http://www.kellyaerospace.com/

The starter gear is probably extended by the drive and should retract when spun up after start. Make sure its gear matches the ring cogs, either 122 or 149.

[asav8tor]

Don't try to start the engine with the ring gear loose as you describe. You must remove the flywheel because your ring gear/flywheel combo are not going to work together no way. I'm wondering if that ring gear is broken/cracked somewhere releasing the normal interference fit. I thought the different tooth count ring gears were the same size but perhaps they are not. If that's the case you might also need a different flywheel to get the correct tooth ring gear to match your starter. To install a new ring gear you heat the ring gear in the oven and chill the flywheel in the freezer.

[Brian Vickers]

I educated myself by checking with vendors. My flywheel is not serviceable and most likely not repairable. Superior Specialties Services said they are not aware of a vendor that works on flywheels so mine is probably junk; certainly not airworthy as-is.

The starter is also not serviceable. The starter parts vendor said the Bendix drive is the likely problem. This is the weak link on the old automotive style units that have been in use for decades. I can purchase a new Bendix drive for $67 plus shipping. I'll probably stew on this for a while since my airplane is still a "project" for a few more months.

Thanks again for taking a stab at assisting me.

[Geico266]

Brian, Dave has it right about the starter. It will retract on the 1st start up. Same thing happened to me and I thought the starter was bad. The local FBO showed me how it worked.

The ring comming off is a deal killer. Time to just the flywheel and starter ring and start over.

[asav8tor]

If you go to the link David provided it describes the Kelly starters as not having a Bendix. The vendor you talked to is not familiar with your starter.

And if your ring gear is broken that would explain why it is loose. A new ring gear might be all you need.

[Brian Vickers]

I'm glad I posted on these problems. I'll leave the starter on the engine and move on. I will also pull off the flywheel and examine the ring.

Thanks again - onward ho!!

[Geico266]

Originally Posted by Brian Vickers

I will also pull off the flywheel and examine the ring.

No you can't JB Weld it on.