That is an astute suggestion. A bad capacitor will act up with roughness, backfiring, and intermittent operation.n2582d wrote:Might want to check the magneto capacitor.
Mag drops with new engine
Moderators: GAHorn, Karl Towle, Bruce Fenstermacher
Re: Mag drops with new engine
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons.
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons.
Re: Mag drops with new engine
Can a severe drop be due to the fact that you are switching off the upper plugs, and the lower plugs are fouled with oil due to new rings?
- mmcmillan2
- Posts: 161
- Joined: Sat Jul 04, 2020 9:30 pm
Re: Mag drops with new engine
I don’t think they drifted, I think they were never set right. I should have left the plane at my mechanic (1.5 hr drive from home) when I found the big mag drop and the engine not idling below 1160rpm. Mechanic said it was ready to pickup, but he wasn’t there when I got it. I called him and he said to run it 5 hrs then tune it.Joe Moilanen wrote:I've never had my timing drift that much from new or rebuilt mags breaking in before. I don't think I've ever experienced more than 1 or 2 degrees drift for any reason, YMMV. I think I'd monitor the points gap if the trend continues?mmcmillan2 wrote:Mine do have the Bendex mags. Type S6LN-21. Overhauled 8/22.
I was in a hurry to fly it home then head to work so I took it. The next day I found the throttle arm on carb was set incorrectly, and full range stop to stop wasn’t available. I fixed that with help of a local mechanic. Then I got a local guy to help retime left mag but he hadn’t done one in a coon’s age and it took 4 hours.
170B owner, KCFD, CFI(I), ATP Multi
- mmcmillan2
- Posts: 161
- Joined: Sat Jul 04, 2020 9:30 pm
Re: Mag drops with new engine
That’s what my installer mechanic thought, but after cleaning plugs it was still dropping excessive. Had to adjust timing.Iurii S. wrote:Can a severe drop be due to the fact that you are switching off the upper plugs, and the lower plugs are fouled with oil due to new rings?
170B owner, KCFD, CFI(I), ATP Multi
- mmcmillan2
- Posts: 161
- Joined: Sat Jul 04, 2020 9:30 pm
Re: Mag drops with new engine
Thanks, will look into that.n2582d wrote:Might want to check the magneto capacitor.
170B owner, KCFD, CFI(I), ATP Multi
- mmcmillan2
- Posts: 161
- Joined: Sat Jul 04, 2020 9:30 pm
Re: Mag drops with new engine
As of yesterday, my mag drops were 75 left and 50 right. Better than 150 left / 15 right for sure. Engine sounds smooth.
Mechanic A was a friend that helped me out. He spent 4 hours on the left mag. He hadn’t done one in a long time, and didn’t have the Bendix P-lead adapters.
Mechanic B was a local one, he set right mag in less than an hour.
For anyone going down the road of mag timing, buy a pair of new gaskets first. Both of mine split while adjusting.
Mechanic B noticed I didn’t have any excess wire hanging out of my mixture cable attachment. It seems that cable should have been replaced when mounting new engine. Further reading in the books showed me that the clamps for the cable housing shouldn’t be aluminum construction, nor or rubber dampened. Mine is poor looking aluminum with some electrical tape. Parts on order from Spruce.
Mechanic A was a friend that helped me out. He spent 4 hours on the left mag. He hadn’t done one in a long time, and didn’t have the Bendix P-lead adapters.
Mechanic B was a local one, he set right mag in less than an hour.
For anyone going down the road of mag timing, buy a pair of new gaskets first. Both of mine split while adjusting.
Mechanic B noticed I didn’t have any excess wire hanging out of my mixture cable attachment. It seems that cable should have been replaced when mounting new engine. Further reading in the books showed me that the clamps for the cable housing shouldn’t be aluminum construction, nor or rubber dampened. Mine is poor looking aluminum with some electrical tape. Parts on order from Spruce.
170B owner, KCFD, CFI(I), ATP Multi