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HM80 magnet almost dead.

#1

T

Trout bum

I have a Tecumseh HM80 motor with a points ignition that has a very weak spark that I traced back to a “dead” magnet in the flywheel. By weak I mean it will not even hold a small screwdriver from the magnet. Is there anyway of replacing the magnet or having it recharged? The magnet is not glued to the flywheel it looks as if it is fastened by means of two pins or dowels.
The motor is from an old go kart for my grandson for Christmas. Thanks

Jack


#2

StarTech

StarTech

I'm afraid those are not available any longer as the Tecumseh company that made that engine has been out of business since 2009. But post the spec number and someone might still a flywheel in New Old Stock.


#3

Hammermechanicman

Hammermechanicman

There are vids on utube of guys recharging flywheel magnets.
Back in the old magneto days "recharging" the magnets was routine maint. I have never tried it you might give it a try.


#4

StarTech

StarTech

Just if you try this you must polarize the magnet the correct way as if reverse it would be the same as a dead magnet.


#5

Hammermechanicman

Hammermechanicman

Does it matter on point systems?


#6

StarTech

StarTech

Depends really. If you have an electric start setup then you voltage problems. I know that AC and DC can exist in the same circuit but I kinda Negative voltages could co exist with Positive voltages in the same. Never tried that experiment. Beside I think the condenser is an electrolytic capacitor which don't like being reversed biased. I just haven't experimented with old point systems to see if the reverse biasing causes problems.

Otherwords if the magnet is the polarity instead having a negative ground system you then have a positive ground system.


#7

A

Auto Doc's

Hammermechanicman said:
Does it matter on point systems?
Click to expand...
Hello Hammermechanicman,

Yes, the magnet is needed to quickly "energize" the coil. The points then break the magnetic field so the energy collapses and fires the coil secondary to the plug.


#8

A

Auto Doc's

Trout bum said:
I have a Tecumseh HM80 motor with a points ignition that has a very weak spark that I traced back to a “dead” magnet in the flywheel. By weak I mean it will not even hold a small screwdriver from the magnet. Is there anyway of replacing the magnet or having it recharged? The magnet is not glued to the flywheel it looks as if it is fastened by means of two pins or dowels.
The motor is from an old go kart for my grandson for Christmas. Thanks

Jack
Click to expand...
Hi Trout bum,

Check out Ebay, there are always flywheels posted on there.


#9

Hammermechanicman

Hammermechanicman

Auto Doc's said:
Hello Hammermechanicman,

Yes, the magnet is needed to quickly "energize" the coil. The points then break the magnetic field so the energy collapses and fires the coil secondary to the plug.
Click to expand...
The question was does the magnet polarity matter on a magneto system using points?

I am quite familiar how ignition systems work.


#10

StarTech

StarTech

Honestly I never checked about if polarity matters on points but I am the Capacitor is electrolytic which are usually polarity sensitive.

The problem is parts availability lately on about everything. And if they are available want an arm and leg in return for some of them.

Working on a Gravely HD52 here that needs brake cable final pull off springs. Heck the cheapest not counting shipping is $28 each. And forget checking Sears as they asking double that price. So I am going some aftermarket springs which just got the spring right on which was $3 each. Then it is the terminals that got to replaced, a voltage reg, and front spindles bushings. Must be one rough yard the operator cutting as all four bushings are busted.

And I got to keep the cost down as the owner is a cheapskate.

What kinda pisses me off is that I got a Gravely factory in my county but can't buy parts direct.


#11

K

kjonxx

You could drill the center of the magnet facing the coil and glue in a neodymium magnet, they are much stronger


#12

Hammermechanicman

Hammermechanicman

StarTech said:
Honestly I never checked about if polarity matters on points but I am the Capacitor is electrolytic which are usually polarity sensitive.

The problem is parts availability lately on about everything. And if they are available want an arm and leg in return for some of them.

Working on a Gravely HD52 here that needs brake cable final pull off springs. Heck the cheapest not counting shipping is $28 each. And forget checking Sears as they asking double that price. So I am going some aftermarket springs which just got the spring right on which was $3 each. Then it is the terminals that got to replaced, a voltage reg, and front spindles bushings. Must be one rough yard the operator cutting as all four bushings are busted.

And I got to keep the cost down as the owner is a cheapskate.

What kinda pisses me off is that I got a Gravely factory in my county but can't buy parts direct.
Click to expand...
I don't think the condenser is electrolytic as it is just used as a snubber in the circuit. I have used the same cap in old Ford positive ground tractors and newer Fords with negative ground systems. I tore one apart once and the paper insulator had no electrolyte on it just dry paper so that one was not electrolytic. Others my be different.


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