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how to wire an old (mid 70's) 5 hp B&S engine ignition

This is a discussion on how to wire an old (mid 70's) 5 hp B&S engine ignition within the Small Engines forums, part of the Tech Support Forum category. Hello - help - I am rebuilding an old 5 hp B&S Huffy lawn mower engine(1970's vintage). Surprisingly, I am


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Old 04-22-2009, 10:33 AM   #1
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Hello - help - I am rebuilding an old 5 hp B&S Huffy lawn mower engine(1970's vintage). Surprisingly, I am able to get the replacement parts I need but...
All the igition wires are either cut off or missing. This is the old capacitor (with the point on the end , a single breaker point and an armature with 3 wires: 1) big fat spark plug wire, 2) medium sized wire and 3) a small uninsulated wire (possible a ground). Where does the wire attached to the capacitor come from? Is it the middle sized wire from the armature? Is the small wire a ground? Where does the wire for the engine kill go. Thanks for any help.
shadester

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Old 04-22-2009, 03:08 PM   #2
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Install a Magnetron ignition coil, # 397358 and there's no issues other than hooking up a kill wire to the coil. And you will never have to change points again, very reliable ignitions.

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Old 04-23-2009, 12:49 AM   #3
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I'd completely agree with this. Even though i can't say that that's the exact model number of the coil that fits on your block, these motor castings haven't changed in at least 35 years. Because of this, even the 70's motors can use current parts, and today's ignition parts are highly superior to the old points style systems. Unless you're a nostalgia fan, which i can understand, there's no other reason not to switch this thing over to use a new ignition system. The Magneto type coil has the same single wire coming off of it, but rather than connecting to points and a kill switch, it just connects to a kill switch.

I don't know if you're going to open it up, but if you find yourself pulling the oil pump apart, (or oil splasher if it's a side-shaft motor) you might want to replace that with new parts too.

If you do open it up, change all the gaskets and seals, and pop in some synthetic 4x4 blend oil in there, and that will greatly extend the life of the motor.

Post back if you have any more questions.
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Old 04-23-2009, 08:45 AM   #4
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Quote:
Originally Posted by shadester2004 View Post
Hello - help - I am rebuilding an old 5 hp B&S Huffy lawn mower engine(1970's vintage). Surprisingly, I am able to get the replacement parts I need but...
All the igition wires are either cut off or missing. This is the old capacitor (with the point on the end , a single breaker point and an armature with 3 wires: 1) big fat spark plug wire, 2) medium sized wire and 3) a small uninsulated wire (possible a ground). Where does the wire attached to the capacitor come from? Is it the middle sized wire from the armature? Is the small wire a ground? Where does the wire for the engine kill go. Thanks for any help.
shadester
I had to go look at an old coil to refresh my memory, the plug wire is obvious, the bare wire goes under a coil mounting bolt (grnd), and the insulated wire goes to the condenser. If it has a remote kill switch, that wire also goes to the condenser.

Install new points, don't try to reuse old ones. The 397358 coil fits ALL B&S 3.5 to 5HP engines, that originally had 2 leg coils.
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Old 04-23-2009, 10:49 AM   #5
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Thanks for all the info. It all seems to match what i'm looking at. I've already replaced the rings, oil slinger, lapped the valve seats and replaced the point and capacitor. Now i can finish this engine and hopefully do some sit-down grass cutting! thanks again for your help. shadester

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