Tecumseh lighting coil magneto/flywheel question

cfh

Well-Known Member
#1
I have a lighted magneto for a Tecumseh, i believe it came from a 1972 HS40 rupp roadster. Also have a Tecumseh allow flywheel #610769a. I have a freshly rebuilt HS50 engine from 1975 (so it has the same flywheel taper as the HS40), which I wanted to put on the lighted magneto and alloy flywheel

Seems easy enough right? Install a new condenser, and file the original points (don't like replacing points as new one never seem "right"), set the points to .020" gap, set the points timing to .035" btdc, and off we go right? but no, i can not get the engine to fire. It kind of tries, spits a bit, but that's about all i get.

So i put a stock magneto (non lighted) with new condenser, filed points set to .020", set timing to .035" btdc, and a #32517 alloy flywheel (non-lghted) on the motor. And it fires right up.

Maybe the lighted magneto is bad? I have a *second* lighted coil magneto, try that, and again, the engine will not fire.

So on a fluke, i install a different flywheel on the same lighted magneto. This flywheel is cast iron with all the magnets. Damn fires right up, and the lights work great.

So what's the deal with this #610769 flywheel? why won't it allow the motor to run??? I really wanted to use this flywheel, as it's lighter weight than the cast iron version, and it would allow me to put an old style rounded blower housing on the engine.

I put then engine with the cast flywheel on this Speedway Red Baron bike. it runs great. just wanted the alloy flywheel for better performance...
http://www.pinrepair.com/minibikes/p/speedway1972redbaron_mine3.jpg

thanks!
 

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#2
That is strange, I built two older HS50's lighted with what looks just like what you have but I don't know what flywheel part number it was. I had no issue with them running. Your flywheel magnets look like they are worn from something rubbing, did you check for magnitism? Could they be weak?
 

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cfh

Well-Known Member
#3
I’ve never had a fly wheel with weak magnets. Not even sure how to measure that. Or if they are weak how to rejuice them?
 
#4
I use a spring gauge which has a spring steel arm. but just use a flat piece of steel and see if they all can pull the same. ALNICO magnets lose strength over time and can be re-magnetized. Look for someone who does magneto repair a lot of them have re-magnetizers. I am just guessing at this as a possibility, you could use a spark tester that has the adjustable gap and check if there is a strength difference from the flywheel that works and the aluminum one that doesn't. I can send you a pic if the tester I am referring to if you are unfamiliar with it.
 
#5
I had the exact same thing just happen to me!! Scratched my head for days….took it all apart inspected everything and reassembled…. Not even a spark the first time…put on another flywheel and stator plate…..fired right up….used that stator plate on another motor no issues….do not know what was wrong….never will probably

my first thought was the coil….but not now….
 

markus

Well-Known Member
#6
Looks like you have a crack at the keyway in the taper insert. looks like it goes all the way through to the outside and even possibly out of round/moved (see the 2 chunks of casting on the face) as well. Goes along with all the damage on flywheel itself, broken fins here and there, taper all gouged up, visible cuts from the mag coming in contact with the wheel, cup securing ears rounded off, She spun loose because of careless installation and went to town. If it did get knocked out of round could be an air gap issue.

There is a simple test noted in the Tecumseh manuals for magnet strength which is a good place to start, but probably no smart to run a flywheel in that condition on an ungoverned engine.
 

cfh

Well-Known Member
#7
So when I wanna test a lighted magneto, I hook up a couple alligator clips to the magneto, ground, and a number 44 bulb. with the spark plug removed, spin the crank with a drill. I did notice the 44 light was not as bright on the alloy flywheel, as it was with the cast iron fly wheel. Which would lead me to believe your theory about weak magnets could be correct. I just never thought the magnets would go soft enough so that it doesn’t fire. Just doing the spark plug test There was spark by the way…
 
#8
Remember that air is an insulator and under compression the voltage required to fire the plug is greater than when it is sitting on the engine. Now if it had a bright blue spark pulling it over with the plug out then it should be more than enough to start the engine, if the spark was faint and yellowish then it could be to weak to run it. This is the tester that allows you to see how big a gap it can jump.
Spark Plug Tester High Energy Ignition System Coil Engine Diagnostic Test Tool | eBay
 
#9
Remember that air is an insulator and under compression the voltage required to fire the plug is greater than when it is sitting on the engine. Now if it had a bright blue spark pulling it over with the plug out then it should be more than enough to start the engine, if the spark was faint and yellowish then it could be to weak to run it. This is the tester that allows you to see how big a gap it can jump.
Spark Plug Tester High Energy Ignition System Coil Engine Diagnostic Test Tool | eBay
Just ordered one! Thanks
 

Venom38

Active Member
#10
I had the same problem as you, cleaning the stator solved the problem. Eliminate all the rust of magnets and it had spark like it never had before. I use the same flywheel as you, so I grabbed the flywheel and stator off another motor and I had instant spark. Then I used that stator with my flywheel and had great spark, which lead me to the stator was the problem.
I have a lighted magneto for a Tecumseh, i believe it came from a 1972 HS40 rupp roadster. Also have a Tecumseh allow flywheel #610769a. I have a freshly rebuilt HS50 engine from 1975 (so it has the same flywheel taper as the HS40), which I wanted to put on the lighted magneto and alloy flywheel

Seems easy enough right? Install a new condenser, and file the original points (don't like replacing points as new one never seem "right"), set the points to .020" gap, set the points timing to .035" btdc, and off we go right? but no, i can not get the engine to fire. It kind of tries, spits a bit, but that's about all i get.

So i put a stock magneto (non lighted) with new condenser, filed points set to .020", set timing to .035" btdc, and a #32517 alloy flywheel (non-lghted) on the motor. And it fires right up.

Maybe the lighted magneto is bad? I have a *second* lighted coil magneto, try that, and again, the engine will not fire.

So on a fluke, i install a different flywheel on the same lighted magneto. This flywheel is cast iron with all the magnets. Damn fires right up, and the lights work great.

So what's the deal with this #610769 flywheel? why won't it allow the motor to run??? I really wanted to use this flywheel, as it's lighter weight than the cast iron version, and it would allow me to put an old style rounded blower housing on the engine.

I put then engine with the cast flywheel on this Speedway Red Baron bike. it runs great. just wanted the alloy flywheel for better performance...
http://www.pinrepair.com/minibikes/p/speedway1972redbaron_mine3.jpg

thanks!
 

cfh

Well-Known Member
#12
i did a screwdriver test on the magnets. had two flywheels next to each other. the flywheel in question, and a 32517. The magnets on the 610769 are definitely weaker. so i guess now the question is, how do you make them stronger?
 
#13
Kids don't try this at home, found this on the Web.

Take a weakened magnet and touch one of its poles to the opposite pole of a strong neodymium magnet. Also, look for a clear indication of the two poles. Also, pay attention to differentiating the South Pole from the north pole. Be careful while you’re using very powerful neodymium magnets. The strongest neodymium magnets indeed find use in modern applications in industry, production, manufacturing, science, but at the same time, they become too strong to handle.
How do you recharge a magnet? When you have the neodymium magnet, find out which end is the North Pole and the south pole. Bringing a compass near neodymium magnets North Pole means that the needle will be pointing towards the south. Holding it near the South Pole proves that it will be pointing north. Utilize this similar method for the magnet you want to remagnetize. Colour mark the poles with different colors for better identification.
After just identifying the poles of both of the magnets, take a weakened magnet and touch the northern pole with the south pole of the neodymium magnet. Then, repeat the process in reverse. In that case, make sure of taking the south pole of a weakened magnet for touching the north pole of the neodymium magnet.

How to remagnetize a magneto rotor?
Make contact and charge all the poles on the rotor simultaneously. Try to match the size of the magnets with the pole face. Go with rare-earth permanent magnets.
 
#14
Kids don't try this at home, found this on the Web.

Take a weakened magnet and touch one of its poles to the opposite pole of a strong neodymium magnet. Also, look for a clear indication of the two poles. Also, pay attention to differentiating the South Pole from the north pole. Be careful while you’re using very powerful neodymium magnets. The strongest neodymium magnets indeed find use in modern applications in industry, production, manufacturing, science, but at the same time, they become too strong to handle.
How do you recharge a magnet? When you have the neodymium magnet, find out which end is the North Pole and the south pole. Bringing a compass near neodymium magnets North Pole means that the needle will be pointing towards the south. Holding it near the South Pole proves that it will be pointing north. Utilize this similar method for the magnet you want to remagnetize. Colour mark the poles with different colors for better identification.
After just identifying the poles of both of the magnets, take a weakened magnet and touch the northern pole with the south pole of the neodymium magnet. Then, repeat the process in reverse. In that case, make sure of taking the south pole of a weakened magnet for touching the north pole of the neodymium magnet.

How to remagnetize a magneto rotor?
Make contact and charge all the poles on the rotor simultaneously. Try to match the size of the magnets with the pole face. Go with rare-earth permanent magnets.
Sounds familiar to "Flashing" a generator that quits putting out.

Not sure why that wouldn't work?

Keep us posted please and let us know how it does?
 
#15
Kids don't try this at home, found this on the Web.

Take a weakened magnet and touch one of its poles to the opposite pole of a strong neodymium magnet. Also, look for a clear indication of the two poles. Also, pay attention to differentiating the South Pole from the north pole. Be careful while you’re using very powerful neodymium magnets. The strongest neodymium magnets indeed find use in modern applications in industry, production, manufacturing, science, but at the same time, they become too strong to handle.
How do you recharge a magnet? When you have the neodymium magnet, find out which end is the North Pole and the south pole. Bringing a compass near neodymium magnets North Pole means that the needle will be pointing towards the south. Holding it near the South Pole proves that it will be pointing north. Utilize this similar method for the magnet you want to remagnetize. Colour mark the poles with different colors for better identification.
After just identifying the poles of both of the magnets, take a weakened magnet and touch the northern pole with the south pole of the neodymium magnet. Then, repeat the process in reverse. In that case, make sure of taking the south pole of a weakened magnet for touching the north pole of the neodymium magnet.

How to remagnetize a magneto rotor?
Make contact and charge all the poles on the rotor simultaneously. Try to match the size of the magnets with the pole face. Go with rare-earth permanent magnets.
Holy crap….you lost me with kids don’t try this at home….HAHAHA!!

I actually found several nice earth magnets in old PC hard drives etc….can barely pull them off the tool box….curious if they are they the same as you speak of here?
 
#17
I had weak or no spark on 2 engines after replacing points, condensers and coils. I swapped the flywheels with others I had and now I have great spark. Thanks to all for the help.
 

cfh

Well-Known Member
#18
Well the answer on my Tecumseh 610769 alloy flywheel is now obvious. I bought a Tesla meter and the 610769 magnets come out at about 22mT. Compare that to the magnets for a tecumseh 32517 flywheel where the magnets measure about 45mT. So there you have it, weak magnets on the 610769, about half the strength they should be.

The Tesla meter is interesting as it also tells you whether the magnet is north or south which is kinda handy.

but the big question is, how do you rejuice the magnets? Because the 610769 flywheel as it sits is pretty useless unless the magnets can be re-powered.

C3883557-ECE8-4B0C-BDEE-96229F8A9539.jpeg
6108FDBD-7FB5-46F3-822D-AC98AB223EAA.jpeg
 
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