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TomF

B-112 conversion to Magnetron

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TomF
Dear Friends, We have a B-112 that needs new points. Instead of getting new ~$20 points, we are looking into installing the Briggs #394970 Magnetron kit. The kit is about $11. We have two concerns: 1. Is it recommended to set the timing using the points before switching to Magnetron? 2. Do most starter-generators this old have enough power to spin the engine fast enough for the Magnetron to work? Any/all comments are appreciated!

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RobS
quote:
Originally posted by BLT
Amoung other things, you will need to change polarity of magneto (flywheel). Briggs had been doing it no charge, you pay the freight both ways.
That's it right on the money - you will have to send the flywheel to B&S to be re-polarized - As long as you have a battery on board I would go with a 12V coil setup and bag the magneto ignition if your having problems with it.

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Kent
Have you considered replacing the points with an aftermarket electronic trigger (often called electronic ignition)? Then you wouldn't need to repolarize the flywheel. It's a simple addition that can be done in a few minutes, for less than $20... Are you sure that is a Magnetron ignition that's being priced that low? It sounds too low to me -- it may be an electronic trigger...

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RobS
quote:
Originally posted by RobS
quote:
Originally posted by BLT
Amoung other things, you will need to change polarity of magneto (flywheel). Briggs had been doing it no charge, you pay the freight both ways.
That's it right on the money - you will have to send the flywheel to B&S to be re-polarized - As long as you have a battery on board I would go with a 12V coil setup and bag the magneto ignition if your having problems with it.
Also - if you havn't already - you will not have to pull the engine to go with the coil ignition ^

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BLT
quote:
Originally posted by Kent
Have you considered replacing the points with an aftermarket electronic trigger (often called electronic ignition)? Then you wouldn't need to repolarize the flywheel. It's a simple addition that can be done in a few minutes, for less than $20...
Doh!!! I forgot. I have had a Sten's Mega-Fire electronic trigger for about 14 years on my 7010. Never a problem. Going price today is about $15.00 and installation should be no more then 30 min.

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RobS
quote:
Originally posted by Kent
Rob, a coil ignition conversion still requires points, doesn't it?
Yes but the magnetron requires pulling the engine and flywheel. The coil and points are cheap, much less than the magentron, flywheel shipping not to mention the labor time involved

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Kent
Rob, with an electronic trigger it solves both problems -- it replaces the bad points and you don't have to pull the engine and have the flywheel repolarized... and it's much less money. The advantage of the coil is that it fires just as hot a spark on the first engine revolution as it fires with the engine running wide open, whereas the original magneto often requires the engine to turn over a few times for it to give a good, hot spark... Back to his original question -- a Magnetron will work just as well with a starter-generator as the points system does -- both are getting their spark from a magneto running off the flywheel. The Magnetron simply uses that magnetic pulse from the flywhee magnets to also "trigger" the fire to the sparkplug. Converting to a coil-based ignition (which will still require points or an electronic trigger) will give a hotter spark during startup -- which can mean better/faster cold weather starting... I have one tractor (2012) running points. I have another running a Magnetron (1989 replacement 10HP in my Big Ten). I have another with an aftermarket electronic trigger (the 3112V)... I can't tell the difference in cold-weather starting between the three. I have a 9HP Landlord that's been converted to a coil ignition, but it runs so rough right now (low compression and smokes) that I can't really honestly compare it...

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RayS

Try this electronic module they work great and you don`t ever have to mess with points again. Just hook it up and forget about it. Best of all you don`t have to send the flywheel in to have repolarized. Here is one on ebay now made by Stens http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=50377&item=4345122040&rd=1&ssPageName=WDVW there is a Mega Fire 1 an 2 and they both work fine.

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BillC
I just recently converted my 10HP B&S, model 243431 engine in my 725 with a starter/generator over to the Magnetron ignition, after I was unable to get any spark from a Stens Mega-Fire ignition module no matter how I wired it. Called Stens to talk to a technician and the women who answered the phone told me they can only talk to distributors. PISSED ME OFF because I have called and talked to B&S, Kohler and Simplicity service technicians many times for help. If you decide to pursue the Magnetron, you have (2) options: 1)install the Magnetron ignition kit, B&S part #394970, which replaces the points but uses your existing armature or 2) install the Magnetron armature, B&S part #398811, which replaces both the points and existing armature. I chose to install the armature, cost $40.00. Spark has a sharp crisp snap to it and is very bright as compared to the points ignition. It also fires every revolution of the crankshaft. You will have to remove the engine to remove the flywheel and either ship it or take it to B&S for repolarizing. If shipped, my understanding is you pay shipping there, B&S pays shipping back to you. You will obviously need a flywheel puller and a 1-1/4" (I think) deep socket to remove the flywheel. Send or take the flywheel to: Menomonee Falls Distribution Center W148 N9121 Patrita Drive Menomonee Falls, WI 53051-2272 Dock #23 I had my wife take the flywheel to B&S, took 5 minutes to repolarize it and she brought it home with her.

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powerking_one
Tom, Those Mega-Fire and other similar modules are a voltage detection type device. There is no hard timing/rotational position reference of when it is supposed to fire unlike the Magnetron. Generally they work fine, but the armature (coil) timing position becomes more sensitive than with points if it's off. In theory, one could use a Magnetron with a 12 volt coil and have the best of both worlds? I'd like to try that setup sometime to prove or disprove it. Ah, another queued project. Tom(PK)

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