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

shadester2004 · 04-22-2009, 11:33 AM

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

k2skier · 04-22-2009, 04:08 PM

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.

Volt-Schwibe · 04-23-2009, 01:49 AM

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.

k2skier · 04-23-2009, 09:45 AM

Quote:

Originally Posted by shadester2004

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.

shadester2004 · 04-23-2009, 11:49 AM

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

04-22-2009, 11:33 AM	#1 (permalink)
shadester2004 Registered User Join Date: Apr 2009 Posts: 2 OS: xp sp2	how to wire an old (mid 70's) 5 hp B&S engine ignition 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

04-22-2009, 04:08 PM	#2 (permalink)
k2skier Registered User Join Date: Sep 2008 Location: Oregon Posts: 313 OS: XP Home-SP3 My System	Re: how to wire an old (mid 70's) 5 hp B&S engine ignition 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.

04-23-2009, 01:49 AM	#3 (permalink)
Volt-Schwibe Asst. Manager, Automotive Forums; HJT Trainee Join Date: Jan 2003 Location: Behind you, watching you as you type. Posts: 7,372 OS: Click "My System" to view details My System	Re: how to wire an old (mid 70's) 5 hp B&S engine ignition 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. __________________ <signature> TSF is funded by our Admin's pocket, care to help? Power Tip: Subscribe to your thread (Thread Tools) to receive an instant email notification when you get a reply. New Members: Creating a single new thread in the correct section is the best way to assure your thread will receive a reply. </signature>

04-23-2009, 11:49 AM	#5 (permalink)
shadester2004 Registered User Join Date: Apr 2009 Posts: 2 OS: xp sp2	Re: how to wire an old (mid 70's) 5 hp B&S engine ignition 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