magneto timing

Flyingmac100 · Post by **Flyingmac100** » Mon Jul 27, 2009 5:43 pm

Recently had magnetos refitted to Continental O-300 D.
On doing Power check - both to right mag only produced 250 rpm drop, both to left mag only - produced slight increase in rpm. Shut down and left engineer a message.
Have since been told that mags were set up for a 4 cylinder engine and not 6 and that all has now been put right, but, power is down and vibration experienced in flight at 2,000-2,200rpm - has anyone any thoughts on whether the initial mag setting could have caused any damage?. Would add that prop has also been overhauled and refitted at same time as mags.

G.Dawes · Post by **G.Dawes** » Mon Jul 27, 2009 9:35 pm

six cylinder mags are different inside completely the cams and distributor are totally different, so that isnt the cause
left mag is overadvanced ?
The correct setting for an 0-300 is
Right 26degrees and left 28 degrees .
Check it before you rip your starter up.
one other point If the mags are Bendix were they set up for the correct distributor rotation, it is easy to set up the wrong internal mark.
Regards
Graham

Flyingmac100 · Post by **Flyingmac100** » Tue Jul 28, 2009 4:56 pm

Thanks Graham. Looks like I've been spun a yarn about the timing.
Prop is being blamed for the vibration and has been sent back for re-balancing. Just have to wait and see what comes out in the wash.
Flying a Eurostar while the spamcan is grounded, so not suffering!.
Thanks again.

J.C. · Post by **J.C.** » Wed Jul 29, 2009 8:10 am

If it was your engineer ( not clear from your post) that told you the mags were set for a 4cylinder, then I suggest you get a new engineer ! Pronto!!

G.Dawes · Post by **G.Dawes** » Wed Jul 29, 2009 9:40 am

Unless the prop was damaged in some way it is unlikely to be out of balance now if it was alright before. Loss of power is not a prop issue if it was the correct one, You do not state which AC it is but it sounds like an 'old' C172. if so get more advice from another LAE and tell them what was said before to you.