MTFCA Forum

Hi all and a good December evening.

Many on this forum helped me with magneto troubles already, took your suggestions to clean my timer, a terribly filthy New Day, and the machine has never run or started better!

I gave her an oil change today for the cold weather, used 5W-30, and then encountered some behavior that suprised me to say the least.

I’ve heard of and expirienced a few “free-starts”, turning the ignition on or throwing the spark lever to instantly start a warm motor.
But this time after changing the oil and letting the motor warm itself, I shut her down to lock up the garage.
Came back, turned the Key to MAG and stepped out front to give her a crank. Being as the motor was still relatively warm, I figured just a pull or two would be all she needed. After 5 pulls I became discouraged so I began walking ‘round to turn her key to battery. I hadn’t made it to the key yet, hadn’t even touched the machine, and she roared to life? I’ve never expirienced something like that, but it happened again when I stopped in town. Set the key to MAG, opened the door and stepped out, as soon as my feet touched the ground she started.
Does this sound like some kind of wiring issue or just good coils and new oil at work?

Additionally, my family sends our prayers to those effected by the storms which have ripped through our state of Kentucky, as well as Arkansas, Tennessee and others. Hated to see its aftermath.

Are you sure the switch is on mag and not battery when it free starts? If so, your switch is probably wired wrong.

I’m decently certain the key was on MAG both times, I turn to battery to use the starter so I would guess it’s wired correctly.
I’ve been having problems with the switch though, the machine does not want to run on MAG if I move the light switch back and forth. Maybe that has something to do with it?

Sounds like it is time to have your ignition switch rebuilt.

Tad the starter will turn whether the switch is on Battery or mag unless you’ve wired it to not have power unless the key is on.

That's very odd. I assume these starts are occurring WITHOUT using the starter motor. The engine should NEVER start when the ignition is switched to MAG, UNLESS the engine is being cranked, whether by the starter motor or by the hand crank or by being towed. The engine could start at random when the key is left on BATT position, but that would be very unusual. Ordinarily, a "free start" will occur at the instant the key is switched from OFF to BAT. Always make sure the brake lever is pulled back all the way before attempting to start the car or when working on it. As to why your car is behaving the way it is, I'd guess it's a switch or wiring issue. With the engine stopped and the switch in MAG position, the ignition system should be completely inoperative until the engine is cranked, since there is no current available to the coils unless the engine is revolved by some means. It's important to always have the brake lever pulled all the way back when the car is not in use or is being started, since if the lever is forward and the switch is in any position but OFF, the engine could start unexpectedly if the car rolled forward or if anyone stepped on the starter or moved the engine with the crank. It's important NOT to leave the switch in the BATT position unless you are starting the car, since it could start unexpectedly or it could lead to coil damage or a dead battery if one of the coils is energized with the engine stopped. Always make sure you have an effective parking brake and be sure to use it, and be sure to turn the switch to OFF and take the key with you when you leave the car.

On the first T I bought, I found out that both sides of the switch were wired to battery. What I had thought was running on mag was actually on battery. I switched the wiring and hooked up the mag to the mag terminal. It would only run at certain positions on the timer. In between there would be places where it would not run. Later charged the magnets and it ran fine on either battery or mag.
Anyway, check your wiring and see if both sides of your switch are wired to battery.
Norm

Excellent beautiful car!

Norman, I think a weak mag might allow ignition failure at the AC wave null points, since they'd get "wider" with a weak mag. A good mag would make higher current over more degrees of crankshaft rotation, which would narrow the "windows" near the null points in the AC where the current might be too low to fire one or more coils at some spark lever positions. Out of adjustment coils which require more than normal current to work could also cause it.

Ordinarily, a "free start" will occur at the instant the key is switched from OFF to BAT.

Yes, but not always. There have been several occasions when I turned the switch to BAT, walked around in front of the car, and it started as I was reaching for the crank.

I agree that a free start shouldn't be possible on MAG, and I too suspect a switch problem. I hope battery current hasn't been leaking into the magneto.

Many thanks everyone! I will be working on the switch first. Lang’s sells a repro switch, clawback style matching mine, does anyone have experience with these repo’s?

Other than the strange starts yesterday, the machine has been doing very well thanks to the wise folks on this forum and their help.

A new switch is what you put in to sell the car and you care not for functionality, longevity or reliability

Call Ben Martin and have the old one rebuilt (if it needs it) if you want a reliable and long-lived switch for years of trouble-free ownership

That’s precisely what I needed to know, thank you.

Many thanks again for the wise words. I had fun taking apart and cleaning a very dirty and worn out switch, I also pulled the "contact arms" (not sure what they are rightfully called) out some to get better contact. Now the MAG doesn't cut out when I turn my light switch, and no more confusion on whether I am pulling battery or magneto power.

I am still having free-starts on almost every outing, and I cold cranked the machine on MAG yesterday. Started great and is running good for now.

Thanks all, and have a good Christmas!

On my recently rebuilt 26 Coupe, I retard the spark, advance the throttle a few notches, enrichen the fuel about 1/4 turn, pull the choke and give it 2 or 3 pulls on the crank. Then Turn the switch to battery and it free starts probably 7 out of 10 times.
on my 26 Roadster, I just retard the spark, advance the throttle, enrich the about fuel 1/4 turn, crank it 2 times and turn the switch to battery and it free starts all most every time. I am in the process of rebuilding it now. We will see how it does once it is back together.
Here is a link to the video of the first time that I started the Coupe after the rebuild. I did use the starter, but do not think it was necessary.


https://www.youtube.com/watch?v=5Mc8etrBF9Y