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View Full Version : Cracked mag timing gears, why?



IainR
01-13-2021, 05:28 AM
Continuing with my engine rebuild and continuing to get small nasty surprises that I am very happy I am picking up now! Both my mag timing gears are cracked (see picture below, marked in blue). Anyone have any idea what would cause this? Also any ideas where I can get replacements? I've also put a wanted in the parts section of this forum.
53583

tempdoug
01-13-2021, 08:37 AM
fresno airparts. you want new or used?

IainR
01-13-2021, 08:41 AM
Thanks tempdoug, I'll take what ever I can find! New would be the preference

tempdoug
01-13-2021, 08:43 AM
call bobby at fresno. those 2 are pretty reasonable new. theres also a guy named william pelcher in pretoria, gautang, has a lot of this small continental stuff if you need it yesterday.

IainR
01-13-2021, 08:54 AM
ooof I see the one gear is $875 while the other is $97.50, hopefully a typo!

tempdoug
01-13-2021, 08:57 AM
your looking at the wrong gear for your nonimpulse mag at fresno, i will put up a link for it. i would have to see the other side you your gear but i believe/??? this is the one your looking for.https://www.fresnoairpartsco.com/product/3513-gear-magneto-drive-non-impulse/

tempdoug
01-13-2021, 09:02 AM
ooof I see the one gear is $875 while the other is $97.50, hopefully a typo!

thats not a typo on that style impulse mag gear but lots of good ones around.when you put the mags on make sure the gaskets are just right for meshing the gears perfect, use a straight edge and a calipers, and measure the housing down with the gasket and then measure the mag. and its real easy. and compensate for a little crush on the gasket.

IainR
01-13-2021, 09:22 AM
Thanks for the help tempdoug, I am just going off part numbers! When you say there are lots of good impulse mag gears, do you mean different styles or second hand?

tempdoug
01-13-2021, 09:27 AM
Thanks for the help tempdoug, I am just going off part numbers! When you say there are lots of good impulse mag gears, do you mean different styles or second hand?


those are the only ones im aware of but for the spendy one you pointed out, theres used around, but like your gears they should be checked. personally i would go new for the others.post a picture of the other side of the one on the right, to see if its a impulse mag gear. are both your mags impulse mags?

tempdoug
01-13-2021, 09:30 AM
like this for instance, but get it checked!!!https://www.ebay.com/itm/Continental-1-36066-Magneto-Impulse-Gear/143807999417?hash=item217b9fedb9:g:X7AAAOSwNhNfl16 ~

IainR
01-13-2021, 09:47 AM
Looks like you might be right tempdoug, looks nothing like the spendy gear and a lot more like the 3513

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tempdoug
01-13-2021, 12:07 PM
thats a 3513, me i would buy them both new from fresno, get your mags seated at the right depth. theres gaskets out there as thin as writing paper and as thick, exagerating here, as 2x4s. do some measuring.

IainR
01-13-2021, 12:34 PM
Thanks very much! I can breath easy now. Will do thanks very much tempdoug for all the help

tempdoug
01-13-2021, 01:18 PM
dont ever breath easy, i always tell the wife, "its always something"

wireweinie
01-13-2021, 04:13 PM
I'm curious as to why they cracked to begin with. Is this typical of these gears/engines? Prior prop strike?

Web

BC12D-4-85
01-13-2021, 09:09 PM
Or sudden prop kickback on starting? Don't open the throttle too much and have the timing checked for too far advanced.

Gary

IainR
01-15-2021, 04:35 AM
I'm curious as to why they cracked to begin with. Is this typical of these gears/engines? Prior prop strike?

Web

This engine did have a prop strike a few years ago, allegedly it was shock load tested, but I found a cracked crank shaft and these cracked gears so am dubious!

wireweinie
01-15-2021, 07:41 AM
'Shock load tested'?

Web

PerryB
01-16-2021, 09:30 PM
Maybe the prop strike WAS the shock load test. It ran afterward so it passed the test, right.....?