Still Running Rough! Go Figure!

[jstall]

Re: Still Running Rough! Go Figure!

Thanks everyone for all of your comments.

The reason that I'm talking a fuel issue here is that I have now seen the engine run rough on both mags even though the right mag is the one that checks out bad on the runup sometimes. I've never seen the left mag rough when the right checks out good.

When the engine runs rough on both mags it always does it after I've switched from the rough running right one back to both.

So it does make sense that the bottom plugs (left) could be loading up while its running on the right.

THIS IS KINDA A DUMB AND REDUNDENT COMMENT, BUT TOM, YOU HAVE ISOLATED THE MAG ISSUE BY SWITCHING BETWEEN THEM IN THE AIR OR WHERE EVER TO SEE IF IT CLEANS UP? IT SHOULD IF ITS A MAG

JUST AN IDEA

JS

[Pearson]

Re: Still Running Rough! Go Figure!

I would borrow another mag from someone and replace that right mag. If you still have the problem, then I would look at the carb.

[astjp2]

Re: Still Running Rough! Go Figure!

Check your carb air box hoses for water, maybe it has a low spot and has trapped water. How many hours are on your mags since overhaul/new? If it is over 500, you should send them in, both slick and Bendix need to be checked out at the recommended time because they seem to eat points and capicitors. Tim

[Tom G]

Re: Still Running Rough! Go Figure!

Thanks Tim, the mags have about 220 hours on them since overhaul and the points were replaced at the annual back in the summer of 06. I think I'm going to put some marvel mystery oil in the gas this weekend and see if anything changes. I keep going back to a fuel issue.

[dennispip]

Re: Still Running Rough! Go Figure!

If it is running rough on the right mag and you switch to both, it will run better, but still will be noticably rough while the bad acting mag is doing its thing. The reason is that the plugs on the bad mag will continue their intermittent firing while it is on the both setting. It should smooth out when you go from both to left only, but your power will drop off.

I never did figure mine out until it finally quit all together. Then it ran smoothly, but only had about half the power it usually did. I did not do a mag check while in the air on that occasion, but the mag was finally dead as a doornail when I checked it after landing. I was glad for redundancy. Those mags at 220 hours have some calendar time on them as well and they do not always last as long as we would want them to.

You have either an electical, fuel, or air (mixture) problem though. Good luck sorting though it!

[fearofpavement]

Re: Still Running Rough! Go Figure!

someone mentioned it previously in this thread but if you don't get satisfaction with the myriad of suggestions already given, do take consideration of the mag switch. I have had experiences in the past with mags misfiring due to an internally defective switch. This can be narrowed down by removing the p-leads from the mags one at a time or taking both of them off and seeing if things smooth up. (if you don't have a mixture that will shut off the engine this isn't recommended as there will be no way to kill the engine without turning off the fuel and waiting for your carb to run dry...)

Making the mags "hot" is risky business and not for the inexperienced. It is however a troubleshooting technique that can help track down an obscure problem like you're having.

Ya'll be careful out there...

[jdoran]

Re: Still Running Rough! Go Figure!

Tom,

It's possible that the thing runs great when the fuel bowl is full (after sitting), but when you are running at high RPM, the fuel flow has become restricted causing the missing. In other words, the fuel won't flow to the carb as fast as it is needed at high RPM. Here's what I would do:

Put a bucket or can under the carb, remove the drain plug from the carb, and turn on the fuel. See how much flow you get from the drain plug. If it initially flows fast, but then slows to a trickle, it would indicate a restriction in the fuel system somewhere, or a vent is blocked, etc.

[Tom G]

Re: Still Running Rough! Go Figure!

Thanks again to everyone for their suggestions. I went to the airport today, started her up and the right mag was worse than ever. It got to the point where the rpms cut down so much I thought it might quit. I'm back to ignition again and thinking that the right mag in fact is the problem and not fuel. As for it running rough on the both position i'm thinking that maybe it just loaded up from running on the bad mag because it eventually cleared up.

I got a call this week from a real nice guy in California. He flies an L2 and had some suggestions for me as well. Thanks Dick! He also pointed me towards a shop in California who specializes in these old Bendix mags. I'm going to call them on Monday and see what their take on it is.

Thanks again to everyone. I'll let you all know how it goes.

[dedrekon]

Re: Still Running Rough! Go Figure!

These guys are very good:

Savage Magneto Service
2415 Radley Ct. Ste. 7
Hayward, CA 94544
Phone: 510-782-7081

[Tom G]

Re: Still Running Rough! Go Figure!

Thats the one Vince. Thanks very much.

[fearofpavement]

Re: Still Running Rough! Go Figure!

Tom,

Well, this must continue to be a very frustrating situation for you but take heart in that you will eventually resolve the issue and have a smooth and reliable T-craft again. These discussions are not only applicable to the aircraft in question but can be beneficial to all of us as troubleshooting possibilities for our future problems. Be sure to keep us posted and we'll all celebrate resolution of the problem when it comes time.

[Guest]

Re: Still Running Rough! Go Figure!

Check out Fresno too, you can get a rebuilt mag (exch) for about $300.

Dave

[Tom G]

Re: Still Running Rough! Go Figure!

I spoke to Al today at Savage Magneto in California. He was super nice and took the time to ask me a number of questions. The first thing he wants me to do is check out the switch and the wiring. This is to make sure that it is actually the right mag and that the switch is not reversed and the left one is really the problem. Also the switch itself needs to be checked. The rough running I experienced on both mags makes him think that the switch should be checked before we move on to the mag itself. I'm going to do all of that this weekend and if everything checks out ok electrically i'm going to ship the mag to him for overhaul, of course after making sure that the problem isn't lack of point gap or something else simple.

I highly recommend him since he really took the time with me which amounted to about 30 minutes on the phone. He also asked me go get back to him either way.

I'll keep everyone posted as to the outcome. Thanks!

[Acroeric]

Re: Still Running Rough! Go Figure!

Tom - we just went through the same thing one a new restoration here. It had the older Bendix mags on it and we put new coils, condenser, points, etc. All the parts were NOS and we had the same problem exactly!

We finally took a known good mag and installed it and it cleared right up. Best we can figure is that even thought the coils were new old stock in sealed cans- they must have gone bad. I think we ended up trying 3 new coils all with the same outcome.

We ended up putting a newer set fo Bendix mags on and it runs like a top now. It still bugs me that we never figured out exactly which component was bad.

[Forrest Barber]

Re: Still Running Rough! Go Figure!

Test wires for continuity and correctness to switch, test mag wires with a buzz box, install a known good mag and then rip the other one apart If it is the mag. Intersting thread , wish the ship was here.