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Ring gear replacement

A

alcladrv

Well Known Member
I removed my prop and ring gear to install a new alternator belt on my O-360 with Sensenich fixed pitch prop. The re-assembly went fine as I thought I reinstalled everything in the same location. When trying to check the magneto timing, I find the timing is off by not just one or two teeth, but more like 15 or 20. I assume I'll need to take the prop off again. After I do that, what should I look for to make sure the ring gear is in the correct location during the reinstallation process? I left the magneto as it was and thought I'd ask if anyone has a suggestion or two before I do something really wrong.
Thanks, Mike
 
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Not specifically. I thought my other markings would cover me. But, thanks, that'll give something to verify after I get the prop off.
 
Mag timing pin

I would also make sure the mag timing pin is in the proper hole. sometimes it could be off and seem like it is in the hole but it is not.

One way to check it is once it is all back together, if you have a mag with an impulse coupling, the coupling should click (fire) at TDC on #1. YMMV
 
TDC

You can also check Cyl 1 piston is at Top Dead Center. Then you can align the ring gear with O or TDC with starter alignment hole.
 
The ring gear can be attached to the flywheel in any position; the flywheel has one slightly larger hole (with the "0" mark), which fits over the one prop drive lug with the larger diameter. The timing marks are on the flywheel. If the flywheel does not sit flat on the prop flange easily, it is in the wrong position. Cheers Barry
 
Start with basics.

rich said:
You can also check Cyl 1 piston is at Top Dead Center. Then you can align the ring gear with O or TDC with starter alignment hole.
Click to expand...

This is the most reliable method to be sure. The piston stop method by approaching the pin turning in opposite directions is the fundamental way of finding TDC accurately. Once marked then it is an easy matter to see what went wrong. Regardless of why it is off, you can just remark TDC and your desired timing on the ring. Just document your work for the next guy or . . . I might forget . .:D

Perfection of all the original marking methods and pieces adds no value. But it would help the OCD to sleep better.
 
Another thing that hasn't been mentioned here yet - for mag (ignition) timing
the timing marks on the rear face of the flywheel corresponds to the crank case split line,
the timing marks on the front face of the flywheel should line up with the round divot mark on the front of the starter housing.
 
Couldn't find an "O" on the crank flange. The starter ring gear rocked in place on most positions, so this was the most helpful reply
barryrv10 said:
.....If the flywheel does not sit flat on the prop flange easily, it is in the wrong position.....
Click to expand...

After getting the ring gear to sit flat on the flange and finding #1 compression, I was able verify the timing. Thanks to everyone for their replies.
 
alcladrv said:
Couldn't find an "O" on the crank flange. The starter ring gear rocked in place on most positions, so this was the most helpful reply

After getting the ring gear to sit flat on the flange and finding #1 compression, I was able verify the timing. Thanks to everyone for their replies.
Click to expand...

I will go a bit further here. You need to find the lug with a base that is about 1/32" larger than all the others. Then find the hole in the flywheel that is also larger, then marry them. Just the other day, I helded someone change a belt. Had to bang the flywheel off with a hammer. Some idiot tried to put it on the wrong way and apparently thought brute force was the answer to why it wouldn't go on all the way. One of the regular sized holes was badly deformed from a previous brute force attempt to get that hole to mate with the index lug (the bigger one) and was never cleaned up.
 
Just one more thought
It is possible that some folks changed the clocking on some constant speed props to reduce/change the vibration characteristics...dont ask me how it works though.
Some Rocket guys for sure did this and my recently purchased CS has had it done. So the #1 piston at TDC is a good way to verify
Mike
 
mvs163 said:
Just one more thought
It is possible that some folks changed the clocking on some constant speed props to reduce/change the vibration characteristics...dont ask me how it works though.
Some Rocket guys for sure did this and my recently purchased CS has had it done. So the #1 piston at TDC is a good way to verify
Mike
Click to expand...

Re-clocking the prop should not involve moving the flywheel.
 
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