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Proper Mags for a C4B5

F

F1R

Well Known Member
According to the lycoming parts catalog the C4B5 and the D4A5 use the same counterweights on the crankshaft. Some time ago there was a post/thread that suggested the impulse coupled mag was NOT to be installed on either a C4B5 or the D4A5 engines. Only the retard breaker mag and a slick start is to be used.

I have spent a while searching AD's and this forum and found nothing. Can anybody find a link to the relevant thread or AD.

Thanks in Advance
 
Good for you to be thinking ahead.... I didn't learn of this problem until after I was flying, and my engine was rebuilt by one of the "big name" shops. :mad: I am still learning, but here is one relevant thread:

http://www.vansairforce.com/community/showthread.php?t=102709

and another

http://www.vansairforce.com/community/showpost.php?p=769687&postcount=4

and here is a good post:

N427EF said:
A 250 hour inspection SB1- 98A maybe with the right tools.
Specifically the impulse coupling.

Tools needed: An impulse coupling puller and a rivet gauge.
Maybe this belongs into a different thread but Mr."Slick" Joe Logie was adamant about doing this inspection on affected engines/magneto installation,
saying that he had seen these fail in 300 hours.
He also said he would not fly an engine with 5th order counter weights and an impulse coupled slick mag. This from the folks at the Oshkosh slick booth.
He recommended a slick start module with a retard breaker instead.
(I think I'll just go with a second Lightspeed EI and be done with magnetos.

Quite simple really with the right tools.
Mine showed no noticeable wear around the affected rivets that hold down the pawls. I'll send it in for a 500 hour when it gets there.
slick.JPG


slick1.JPG


slick2.JPG


slick3.JPG


slick4.JPG
Click to expand...
 
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My solution was to run one mag (Bendix) on the right side with NO impulse coupler and run EI for the other ignition utilizing the EI for starting.
 
Weasel has a good solution!
However, I felt that one day I would forget to start the engine on the EI and break "my" teeth off the fly wheel ring gear.

After having inspected my impulse coupling and seeing no significant wear, I am quite confident the impulse coupled mag will go to the 500 hour overhaul mark.

Best to avoid a known SB if you can.
 
Toggle for a 6393

Thanks for the response. I have a slick start on an impulse LH mag (C4B5 IO 540) and would like to change it for the 6393 retard breaker mag. I use toggle switches and would like to know if I can still use a simple toggle with the 6393 or if a key ignition will be needed for the retard breaker set up.

Until now I start with the LH mag only and it works fine. I am uncertain what the toggle requirements will be with the dual points set up in the 6393

Thanks Again.

I have a PM sent to Doug R. but maybe he will see this first.

EDIT: The answer is YES a toggle switch can still be used with the 6393 retard breaker mag. However the 6393 mag will need a different drive coupler as the impulse drive coupler is NOT compatible.
 
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Proper Mags for -C4B5

The Slick SB and Lycoming SB specifically reference the following engines:
O-540 B2B5, B2C5, E4B5, E4C5, G1A5, G2A5 IO-540 K1A5, K1B5, K1G5

The recommended course of action is a 250 hour inspection.

I understand this is the position of a single individual, not Champion. I have asked them to evaluate/clarify their position on this issue.
 
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