Ironflight

Ironflight

VAF Moderator / Line Boy
Mentor
Well, it looks like the left Mag on Louise's RV-6 is finally calling it quits - best we can tell from the logs, it has 1800 hours since new, and the only things done to it along the way have been timing checks. It has been getting harder and harder to start (ignition key that grounds out the right mag in the start position), and we'd rather not get stranded. I took it off and did an E-gap check (close) and internal visual inspection (looked good) today, but now I can't even get it to time right. I consider these to be 2,000 hour mags anyway, so i figure I'll order a new one Monday morning. A couple of questions came up though thought I'd throw them out to the brain trust...

1) The O-360-A1A has a 4373 on the left 4370 on the right. My TMX-0360 has a 4371/4370 combination, which I thought was standard....but looking up the Unison App table, it calls for 4373/4370. the only difference I can find in on line references is the lag angle 4373 is 20 degrees, 4371 is 25 degrees. Anyone know if this really makes a difference? My Mattituck built engine has preformed exceptionally with the 4371....

2) What would make a mag check fine on the bench for E-gap and point opening, but not do a thing on th e"buzz box" when hooked back up on the airplane? That's what I've got now - "It's dead, Jim....". It bugs me that it appeared to be working a little when I took it off - now I can't get it to do anything.

3) Anyone know of a good deal/great price right now? I need to get one first thing Monday morning - Louise uses it to commute, and I'm gonna lose my airplane if her's isn't flying!

Paul
 
As for your first question -- either will work just fine... it doesn't matter which one you order..
 
Ironflight said:
2) What would make a mag check fine on the bench for E-gap and point opening, but not do a thing on th e"buzz box" when hooked back up on the airplane? That's what I've got now - "It's dead, Jim....". It bugs me that it appeared to be working a little when I took it off - now I can't get it to do anything.l
Click to expand...

Paul, I assume you rotated the prop sufficiently to allow the impulse coupling to "snap" prior to checking with the buzz box. If not, the mag will not time properly.

But if it is dead regardless of how you spin the prop, sorry, I don't have any ideas.
 
Last edited:
Sam Buchanan said:
Paul, I assume you rotated the prop sufficiently to allow the impulse coupling to "snap" prior to checking with the buzz box. If not, the mag will not time properly.
.
Click to expand...

Yup - did that, and tried it after goign all the way around a couple times to make sure I had set it up right.

The good news is that I have an offer of a couple Mags to put on tomorrow, so Mikey may make it to work Monday after all!

Paul
 
Hay Paul,

Are you using your buzz box to check the e-gap? I use the Buzz box to set e-gap, if it works on the bench then it should work on the plane, the mag does not know or care where it is, it should work. One thing though if the P-lead is attached then the mag switch must be turned on, if then it does not work, un hook the P-lead and check, you could have a problem with the switch rather then the mag. Or you could have forgotten to re attach the wire that plugs onto the mag when you put the cover back on the mag.

My 4373s are 25 degree lag,,,, interesting.
 
Paul,
Did you hook up the p lead? If so you might have a bad switch. Disconnect the p lead and see if you can time the mag.
Dave (Swift driver)
 
Thanks for all the inputs folks! it is amazing that something as simple as a Slick Mag can cause so many wonderful hours of head scratching - there really aren't that many parts that can go wrong. Fortunately, we have a wonderful RV community, and Ken in Lafayette offered me a pair of mags to use to help figure this out. Since we needed to fly somewhere for lunch anyway, and Louise wanted more RV-8 stick time, we flew over, picked them up, and treated Ken to lunch!

Got home about 1530, installed the replacement, and all is well. I'll TS the bad mag when I have the chance, but Mikey is back in the air, with a stronger starting spark than Louise can remember.

This community is just awesome - I can't imagine an RV'er with internet access could ever be stranded for very long....

Paul
 
Mikey's in College Station

Mikey and I made the commute up to College Station this morning and he's feeling good. Good strong start. Sterling mag check before take-off. :)

Big thank you to Ken Broussard for helping us out (and giving me an excuse to fly the Valkyrie cross-country). I owe you!
 
Just doing the "what's different" check between checking the mag on the bench and on the airplane. You turn the mag gear by hand on the bench, you rotate the mag gear through the prop and associated gearing on the airplane. Any chance that there's an issue with worn gears or improper contact?
 
You must log in or register to reply here.