my 1910 runabout (1917 motor) runs fine on battery but starts to miss fire and backfire when I switch it to mag....any suggestions...quick check fixes??? i am a modern day car mechanic and have already re- built the trans, rear end and fitted a brand new carb to this car, it seems to want to break every time I drive it....I have a 1926 touring car that never missed a beat since I bought it...
Could be a number of things. 1. Dirty mag plug pickup, 2. loose wiring 3. faulty ignition switch. I'd start at the mag plug and see if it is clean. Mike
My money is on the coils not being adjusted properly.
thanks mike...wheres the mag plug????
Lift the floor boards and it will be on the top of the hogs head. Mike
Your's may look a little different, but the location is the same. Mike
mine has some kind of oil pipe that goes to the timing cover but ya i found it thanks...its fine
Might look like this? That is an auxiliary oiler. It's a good thing to have. Mike
now it wont run on mag at all though...so its gotten worse...
Weak magnets will result in poor running and missing as well as the dirty mag plug/pickup. Mine did that and once the magnets were recharged it runs great. You can find good instructions to do the job using 3 twelve volt batteries and a compass here on the forum. Use a sharpie pen to mark the hog's head location for the compass.
Be sure to check the mag output first so you won't be wasting your time if it is a different problem, like a switch or wire problem.
If the missing just started then look for wiring loose or dirty mag pickup as band lining material collects around the pickup and holds oil/metallic particles that can short out.
But usually not intermittent. So if running poor in mag has been from the beginning then the coils should be tuned and tested on a HCCT or Stobospark unit. A 'buzzing' coil may work on DC current but won't on AC current from the mag unless it's been treated to proper settings of the coil points and vibrator bridge gap.
Pull the mag plug out and look in the hole of the hogs head and see if there is any lint on the mag ring contact. Then inspect the plug there should be a point contact that will touch the mag ring when the plug is back in the hogs head. Make sure there is no lint on it.
If these are clean replace the plug and with the wire disconnected from the terminal measure resistance between the terminal and ground it should be near zero. If not (>50 ohms) then either the contact is not making up or there is a problem with the mag ring.
You can check the magneto output, by using a 1156 lamp and volt meter. Disconnect the wire at the mag plug, connect a 1156 lamp between the terminal and ground. Start the engine on battery and lamp should light dimly at idle. Use the voltmeter to measure the voltage, should be maybe 3-5 volts. Then as a higher engine speed the lamp will brighten and the voltage will rise. You should get voltages around 30 voltages at max speed, the lamp will also burn out. Search the forum and you should find the exact spec's for this test. Mike
You say a 1910 T!!!
What kind of coils/ box does it have. The 1913 and older coils were VERY troublesome!! Unlike the rest of the production, which can be very reliable
My '26 touring didn't run well (not terrible, but not well) on mag before or after getting my coils rebuilt by ron the coilman. I guess that means my magnets need to be juiced up?
Maybe follow Mike Zahorik's posting first, just to be sure.
Possibly excess end-play in the crankshaft?
Check the coils. Have had the same and one coil was not okay.
Greetings from germany
several things to check. First is the output from the mag terminal at the top of the hogs head. When the engine is running, it should be at least 6 V AC at idle. Check with analog AC voltmeter. The voltage increases with speed. If this is OK, check the wiring between the mag terminal and the switch. Since, your engine runs smoothly on battery, the problem is not likely to be in the coil box or in the timer. Adjustment of the coils is suspected in this case. Should have new or clean contacts at the points and adjusted as shown in the book "Electrical System" Best way to check is with a Hand Crank coil tester or strobospark. The coils should have good condensers and no double spark. They should spark on every point of the AC wave.
If you have weak spark at mag terminal, first check for the connection at the mag terminal inside the hogs head with the mag plug. No lint or dirt should be here. It should make a good contact with the magneto plug.
Next thing to check is for crankshaft endplay. There should be very little endplay in the crankshaft. This can be checked by first pushing in the clutch pedal and then releasing it. Next go to the front crankshaft pulley with a large screwdriver and pry gently to see if you can move the crankshaft forward. The idea here is to see if the crankshaft moves forward, not to see if you can bend anything. If you get a lot of play, you can stop your test. The fix is a new rear main cap. Some have been successful in building up the surface of the main cap and replace it without pulling the engine. It is very hard to do this with a 4 dip pan. On an earlier 3 dip pan, you will need to pull the engine to do this. Look up previous posts to see how to build up the rear main bearing thrust surface.
If you are lucky and have little endplay in the crankshaft, you can try an in car magnet charge. Sometimes this will fix the problem if none of the above are causing it.
Another temporary fix would be to continue to run on battery, or install a distributor.
Get yourself one of those mag meters from Langs, That will tell you what your mag is doing. Mine at road speed just about full out pegs the meter.
Comprehensive magneto output testing requires serious tools.
A simple voltmeter connected to the magneto post will tell you very little about the health of your magneto.
If you can find a friend with FunProjects St. Louis magneto tester or know someone who knows how to conduct the analog ac voltmeter and 1156 bulb test and understands how to analyze the results you will understand what is really going on with your magneto.
Ron the Coilman