National Aeronca Association Bulletin Board

During the annual the A/I said the timing was so far off on the mags that he needed to remove them and re-position them. I have had two annuals and many more before I owned the plane. There are no entry logs on having the mags out of timing or needing to be adjusted in this manner. The A/I stated that he had turned the mags as far as the limit would allow without removal. He stated that one mag was at 28 degrees and one at 35 degrees. This removal process has not occurred and I would like another opinion.

The plane has always started on one spin and run up to specs on the ground and flown well with fuel consumption as per specs. Does anyone know of what the mag timing should be for this engine. I have Eisemann mags.

If it's a plain old A65 the timing should be 30 BTDC. Timing these 'old timers' (pun intended) is not brain surgury. It's certainly possible to run that far out of time but I think I'd take a look at the internal parts (gear wear) and the point gap before resetting it. Especially if it had not be done for some time. I actually find that the timing pretty much stays put once it's set correctly but has parts wear it will shift slightly from year to year.

MikeB

I also have Eisemanns on my Chief and they are both set at 31 degrees according to the logbook entry from my last annual.

Remember that points wear and as they do the timing changes.

Looking at the A65 manual it states 30 degrees for both mags but I suspect some set them slightly ahead (31 degrees) to compensate for wear (or some say "better power") I don't think a degree one way or the other makes much difference.

Mike

It's tough to see the timing marks on some installations. Each mark is 2 degrees as I recall, starts at 24 and ends at 32 degrees.
If you have the standard plug wire installation, one mag fires two top and two lower plugs, you don't use split timing. Some 65's and the A75 had split timing. But it only applies if a single mag fires all of the top plugs and the other fires the lowers.
You might check the mags for a worn cam or points.
Paul

Thanks to all of you for the information, I will pass it on to the A/I. I will post the adjustment results as soon as it is done.

Well in the fall of 2011 during the annual, I had new Slick magnetos installed. My 41 Aeronca Super Chief did not want to tach over 1900 rpm and it was blamed on magnetos. The new magnetos are installed, along with new shielded wiring harnesses, plugs and cowl bumps. Timing was set at 30 TBDC (so stated in A/I notes) which is standard for this A-65-8.

First time up (solo) and on climb out performance was poor, or so I thought. Using 100LL and some non-alcohol car gas (STC certified), about 1/2 each. On run - up magnetos were very even little no RPM drop on individual mags) I never saw any RPM over 2100, at full power during climb out or at cruise. Could not get the engine over 2100 ever. Used to get 2300 all the time, when needed and could cruise at 90 easily. Cruise on this first flight with new magnetos was never over 85, straight and level. Compression is great on all cylinders (high 70's and high 80's). Flew it at 3/4 to full throttle for about 1 hour. There was little or no difference between 3/4 throttle and full throttle during normal flight as regards engine performance, so I left it at 3/4 throttle for the majority of the flight. Tach stayed at about 2000 to 2100 during this 1 hour of flight.

I noticed what I thought to be a BIG difference with a lot less power with the lower RPM during take off and when flying doing a climb from 3000 to 4000 feet at full throttle the engine seemed to run rough but when leveled out and the throttle brought back to 3/4 it ran smooth.

I have posted several articles on the timing issue with my plane and the old Eisenmann magnetos, that I have now replaced at the A/I recommendations.

Any one have any thoughts on this, as I need the power on take off for a short grass strip with obstacles at the ends. That being said, I am a low time new pilot, have a pretty good knowledge of mechanics and engines. I have very little experience with pre-war Aeroncas, except mine, and trying my best to understand what should be the RPM to expect on full power takeoff roll with say no wind or low wind (4 MPH headwind) on smooth ground.

I would like to get all I can out of this 65 HP engine and it does not feel like it is giving me that now like it did in the past when flying with a CFI during training in this plane.

FYI, I called the A&P who did the Slick install and set this up before I fly again, but am searching for information from you experienced pilots and plane owners.

Thanks,

Any thoughts on this topic would be very much appreciated.

David - aka Skookum

I don't know and this is just a shot in the dark but I saw this once before on a A65 where the mag impulses weren't tripped before final timing which results with the timing being off. That particular engine wouldn't static rev above 1800 rpm. Supposedly the mags (Slicks) were installed by a A & P but I wasn't there at the time. All I know is they were way retarded.

MikeB

A test of the tach might be in order.

Good point Jerry. Sometimes we miss the obvious . The tack on my L16 was off by 150 rpm.
Mike

I will have the tach tested. Thanks.

David Ring aka Skookum