really no expectin an answer??

big job

big job

Well-known member
Going back to Oct, our machine shop did a 1923 engine. Ok we ran it in on
an engine stand with radiator muffler. OK. We tested the mag. terminal with
a 12vt test light, so strong it blew the bulb. OK thats good. I like to run and
run em in on the stand. Alright installed the engine, all good to go. Test drive
eng. normal temp turn to mag oh boy that kicks ***. about a mile, backfire
duh duh duh back to batt kept on going. I write this Dec 31, and the 12vt.
test light is dim more like 6vts. I didnt do anything so whats up? It does have
one of them oilers from the mag. looks good, clean tested with a ohm meter.
So, how can this take an instant dump. .005 crank end clearance which is
within Ok. Dont tell me LOL Im not yankin the engine to replace the coils.
Guess I gotta live with batt position. Again I am getting a weak signal from
the mag. terminal. any thoughts Oh we ran this on the stand for atleast
10hrs with normal everything.> chg. temp voltage etc..
been to all our T guy sites with no avail.................

samuel
 
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With an analog meter what is the AC voltage output of the magneto at idle, medium and approx 20 MPH RPMs now? Was it a rebuilt magneto coil? Could the battery voltage somehow come in contact with the magneto? Take the magneto contact out and check for something jammed in the spring and that it's making contact with the button on the coil ring.
It could also be the switch is making intermittent contact.
 
Don't think a backfire caused the problem but that a weak mag caused a voltage drop and the coils misfired because of it. #1 is as suggested by Red. Pull the mag post & check for lint or poor contact for some reason. If it's band lint put in one of those screen filters that go under the trans inspection cover. It'll catch the stuff before it causes any more problems.
 
Sh-t - Can the mag post oiler and replace with an original - just went through the same exercise.
 
Lint can cause a problem..

My mag died in the middlwe of a parade.
When I got home I found a bunch of lint on the post spring so I cleand it and adde the catch-all screen. No problems since then!

BTW - I have a mag post oiler - When I installed it I made sure that there was significant clearance between the post and elbow so it would not short out.
 
All I know is there is no lint- engine is fresh, it has the screen. I'll try another mag post.
I was just wondering how it took an instant dump like that.
sam
 
They can & will just crap out - base was shorted out - completely rebuilt engine, rewound field coil, recharged magnets - everything new - owner had about a hundred miles on the works, was coming home from a parade and just started running like crap - no rhyme - no reason ! Accessory mag post oiler was the culprit ! Changed it out with an original and it again runs perfect.
 
The only time I have had my T backfire is when I switch from battery to mag, miss fire on mag sometimes, yes.
I would start from the front and work back. Make sure the bolt under the timer is head up. Check timing. Pull the mag contact and check to see if it's shorting. Take the switch apart and see that the contacts are clean and that the rotating part is making good solid contact.
Connect your test light between the mag post and ground, that's your load. Now do a AC voltage check at idle and approx motor speed of 20 MPH. What are your readings?
If it back fired it has to be timing or fuel or the switch is faulty and road vibration causes intermittent contact. The mag post is locked in and can't go any place unless the tip is not making good contact with the button on the ring.
If the mag is weak, you may just need to recharge the magnets. If it's dead, then battery voltage got to it or there is a short in the windings. Was the mag coil ring new rewound or crusty used?
 
No Red, its the same coil or origional coil. It runs fine daily on batt. only. so I my guess
is the coil or coils had a heart attack.. No matter what rpms the mag term hardly lites
a test light around 3 volts.. its just not putting out. so live with it I guess. but for the
first 10hrs run time it did work perfectly.
sam
 
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