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Well It Must Be The Magneto 'cause It Will Run Like This (Video)


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#1 engineguy63 OFFLINE  

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Posted July 08, 2014 - 08:29 PM

Posted Today, 02:25 AM

Well, despite throwing what looks like a good hot spark (plug out of engine) the magneto must have gone bad because it would just not go...HOWEVER if I set it up with an automotive coil...it runs sweat...plus VERY easy starting! Probably gonna re install it in the panzer for the show in CT, but, is there any problem with running it this way?? I know the coil heats up but it is a 6 volt coil and I am only using 6 volts....I do realize the points are closed longer on this engine than the application the coil was designed for....but with an automobile coil firing more often in a 4 or 6 cylinder car and at probably a much higher rpm, my thought was it could handle it.......Am I thinking about it incorrectly???? thanks for your thoughts!

https://www.youtube....eature=youtu.be
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#2 MH81 ONLINE  

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Posted July 08, 2014 - 08:35 PM

Can you put a dropping resistor in line with the coil?

#3 DougT ONLINE  

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Posted July 08, 2014 - 10:53 PM

Can you put a dropping resistor in line with the coil?

If he's only running 6v it may be too much for it. That being said, I've never known a 6 v coil to get warm on a 6v battery.



#4 engineguy63 OFFLINE  

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Posted July 09, 2014 - 05:54 AM

Once running It will stay running if I switch it over to a good 1 1/2 volt dry cell, but once the cell voltage starts to drop it gets sketchy ( I guess 1 1/2 volts is the bare minimum. My thought was if I can drop the 6 volt gell cell to 3 volts...that might be just right....ANY IDEAS on what yipe of in line resister to use and where it would be found?   THANKS!!



#5 HANKG OFFLINE  

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Posted July 09, 2014 - 06:13 AM

Why not replace the mag standard magneto sales Chicago IL 773 2010  about 55.00 dollars


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#6 MH81 ONLINE  

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Posted July 09, 2014 - 06:33 AM

Do you have a different coil? At 6v, a 6 v coil should be pretty cool to warm... Not hot.
As for the resistor : http://www.autozone....sistor/_/N-25rh
I would go with the second one, mainly because the .8 doesn't seem like much, but you should measure the coil resistance too.
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#7 glgrumpy OFFLINE  

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Posted July 09, 2014 - 08:15 AM

This is interesting, didn't know a Briggs could hook up to coil like that. Can you sketch the way it is connected for me? I'm always having trouble with those mag coils. Seems you buy off ebay that say they will work, but then don't. Most have that electronic stuff on them too, and have to reverse polarity or ?? and they didn't work for me either on standard engine. Can't it all just be a 12 volt system like any engine? Guess would hook up like a Kohler then?  Might have to think of that. Hank, might have to look up this place, see if any diff than others? 


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#8 engineguy63 OFFLINE  

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Posted July 09, 2014 - 08:07 PM

Actually, I am gonna replace the coil eventually....or maybe try rewinding it....cant be that hard, and I have made many low tension coils for Hit and miss engines. I don't have the time right now to pull the flywheel and get into all that, and this was the best way for me to confirm it was not a carb problem or something with the points, or some other strange unusual reason it was not running and it makes the engine incredibly easy to start. PLUS I just happen to have an old 6 volt automobile coil I was wanting to use for some good purpose! hook up the battery and even a half hearted tug on the rope and its running....first try everytime!!

take a battery run a wire from the negative terminal to the body of the engine or tractor frame, then another wire from the points will go to the automobile coil, the other side of the coil run to the positive end of the battery and run a high tension leed from the coil to the spark plug.......done! You can add a swith in there if you want as well. I cant see why this would not make even the fussiest old engines come right to life.....any mag even good ones need to get up to speed before there making a nice hot spark.....this way its hot right off the bat.
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#9 engineguy63 OFFLINE  

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Posted July 09, 2014 - 08:15 PM

Also, just a note, I set it up on my back lawn to run today........little over an hour and battery is still good and coil got pretty warm to the touch......about as warm as it would sitting on my driveway for an hour in the sun, so I guess its ok. I'll be able to drive around some shows this summer, and then this winter tear it down and do whatever it needs to be right. (brakes  need to be done as well) engine is back in the tractor and Its gonna go to ZAGRAY next Sunday......see some of you there I am sure!  E


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#10 HowardsMF155 OFFLINE  

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Posted July 09, 2014 - 10:15 PM

I did a similar work-around on a pull start Kohler-engined Gravely two-wheeler.  I used a twelve volt coil and put a 12 volt battery in the unused battery tray.  My coil got quite hot also.  What I figured was that on an automotive engine, the points would be closing and opening 3 or 4 times per revolution for a 6 or 8 cylinder engine, but the little Kohler only opens once every two revolutions, so lots more current was flowing through the coil while the points were closed.  I worked around that by putting a 12 volt 20 watt bulb in line with the points and coil, so the current draw was dramatically reduced.  I put the enclosed bulb on the front of the Gravely and had a "Cyclops" with that little light just glowing away while the engine ran.  No charger for the battery, so I would have to charge it manually, but it worked well for several months like that before I sold it.



#11 engineguy63 OFFLINE  

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Posted July 10, 2014 - 07:01 AM

Hi Howard, I worked out that same idea......points are closed  ALL the time except for that brief moment they open.................if it was designed to run this way...the cam profile would be such that the points close only for a moment just before they open.....and then stay open for the rest of the cycle.......The coil would never heat up.



#12 panzerdan OFFLINE  

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Posted July 11, 2014 - 07:10 AM

Just asking, but did you replace the spark plug with new. I know that I have had spark plugs that will fire outside of the cylinder and not under compression. If the magneto is firing, then it should be as good as it will be because I can't think of any reason for it to get weak. You said you replaced the points and condensor. Even if the spark plug is new, replace it with another new one just in case you have a weak plug. It would be worth a try before you pull the mag. 



#13 DougT ONLINE  

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Posted July 11, 2014 - 10:34 AM

It is possible for a mag to fire the plug outside the cylinder but not fire under compression. My rule of thumb is that it has to be able to jump at least 5 times the plug gap outside the cylinder to be good.



#14 MH81 ONLINE  

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Posted July 11, 2014 - 06:21 PM

It is possible for a mag to fire the plug outside the cylinder but not fire under compression. My rule of thumb is that it has to be able to jump at least 5 times the plug gap outside the cylinder to be good.


My rule of thumb is that if it says Champion on it, it's probably the issue.

#15 DougT ONLINE  

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Posted July 11, 2014 - 09:59 PM

My rule of thumb is that if it says Champion on it, it's probably the issue.

I think the spark plug brand debate is about like the oil brand debate. I've fouled out autolites, delco and a host of others as well. My experience with NGK is that it should stand for No Good Krap but others think different. One thing I was told by a reputable source is that the porcelain on the modern plugs isn't glazed like the older plugs. Modern engines are meant to burn cleaner and more efficient so the manufacturers skip that step. An engine with the carb adjusted right will keep a plug a lot longer than a poor running one. Find new plugs for $1.50-2.00 on sale at Walmart and buy a bunch. Scour the swap area for old stock plugs for the troublesome engines. If it can't jump 5 times the plug gap outside the engine, I don't care what kind of plug you thow at it, it's going to give you fits. I've fudged for a weak mag by setting the plug gap closer.


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