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B&S 5S - Intermittent Spark - Newbie Question

G

Gauge

Guest
First off let me say that I just found this website and I am AMAZED to find a community organized around the preservation of old engines. I am really excited to be a member of the group.

I have a B&S 5s motor that has been in my family for almost 30 years. My father found it in the trunk of a car in a junk yard in the 1970's. He took it home and to his surprise it ran well. He stuck it in the garage and left it there until 1991, when me, as a teenager, decided to restore it. So I took it completely apart, cleaned everything, painted each piece and put it back together. I never put any fluids in it. Instead I put it on a bookshelf in my bedroom, where it sat for the past 15 years. This past weekend I decided to bring it into the garage and see if it would start. I filled it with oil and gas and to my surprise it ran, but only for a short while.

I have to come to realize that the spark plug fires but only for a short while, then the spark gets weaker and weaker until finally there is no spark at all. I replaced the spark plug with a new CJ8, but that had no effect. Same thing, it sparks for little while, then gets less and less until nothing. Could it be the new spark plug is bad? If I hold the wire, it gives me a nice ZAP when I rotate the engine. Any ideas on what might be the problem? Coil? Points?

I am really glad I found this site and I am very happy to be a member. Thanks for having me.
 

Ed Radtke

Registered
Age
62
Re: B&S 5S - Intermitten Spark - Newbie Question

Start by changing the condenser and go frome there.:wave:
 
S

Sky

Guest
Re: B&S 5S - Intermitten Spark - Newbie Question

Ya, what Ed said. Hi Ed! :D
 

BWegher

Registered
Age
63
Re: B&S 5S - Intermitten Spark - Newbie Question

I've seen a condenser work ok to start, then fail after warming up. Had a coil do that, too. Check primary wire insulation where is passes through the backplate for a short or near short. Wiggle the spark plug wire end connector, they also corrode inside where they contact the wire. May need to remake the end connector to reach clean wire.
Make sure the points are clean.
Sometimes ignition problems are hard to find.
 

Andrew Mackey

Moderator
Last Subscription Date
05/14/2017
Re: B&S 5S - Intermitten Spark - Newbie Question

The original plug for your engine is the Champion J-8 it is a non resister plug. Later early resister type was the J-8 J, which had an internal air gap built into the plug, that in turn raised the voltage required to jump the gap. The J-8 C plug you are now using, is made for 2 cycle engines, and has a carbon resister inside. This plug requires more current and voltage to fire, and probably is taxing the coil a bit as well. Try cutting the gap down to .020", and see if it behaves any better. The J-17 & J-19 LM plugs are also resister type, using an internal resistance wire. The original J-8s should be available from one of Harry's sponsers here on the stak, or perhaps you can obtain one at the next show you attend. The comparable plug in AC is the AC LM-46. If you really want to monitor spark on the engine, keep an eye on EBay for the AC LM 46-B spark plug. it has a neon bulb built in, and gives a constant 'visible ignition check' (to quote their advertising).:cool: from the sound of it, everybody here has it nailed - find yourself a new condenser, and make sure there is no corrosion or oil on the points. Keep us posted on your progress, and welcome to the Stak!:)
 

K D Redd

In Memory Of
Re: B&S 5S - Intermitten Spark - Newbie Question

Andrew,
I have to disagee with you. Champion sparkplug that are equipment with a resistor have a type number that has an "R" prefix. A J-19LM is a non-resistor plug. A RJ-19LM is a resistor plug. The "J" suffix is a cut back ground electrode for use on 2 stroke engines.

Kent
 

BWegher

Registered
Age
63
Re: B&S 5S - Intermitten Spark - Newbie Question

KD Redd is right. Andrew is wrong, as usual. The J6J designation just meant the electrode gas was set differently from the regular gap.
Resistor plugs always used the "R" in front of the regular code. Plugs with internal gaps used "U"
 
G

Gauge

Guest
Re: B&S 5S - Intermitten Spark - Newbie Question

Thanks for the responses. I really appreciate it. I will order a new condenser and start there. I have found that ignition problems are the most annoying of all the engine problems I encounter.

Andrew, the thought of a neon plug that is visible as the engine fires sounds really cool to me. I did a search on Ebay and Google for the AC LM 46-B and I could not find anything. I also did a search for a "neon plug" and could not find anything under that as well. Do you have a web link you could post that would show me to a picture. I would really like to see what one looks like.

THANKS TO ALL! You guys are great.
 

John Newman Jr.

Subscriber
Age
64
Last Subscription Date
01/10/2019
Re: B&S 5S - Intermitten Spark - Newbie Question

Gauge,
J.C.Whitney sells spark plug connector caps that have these neon lights in them (For That Custom Look.....)

Harbor Freight sells an inline neon spark checker that you hook up between the plug and wire. See it here
Both of these allow you to see if you are getting a consistant spark while the engine is running.
 

Andrew Mackey

Moderator
Last Subscription Date
05/14/2017
Re: B&S 5S - Intermitten Spark - Newbie Question

I stand corrected on the plug info, by K D Redd, with the one exception:
The J8-C has a Carbon resister. As for pictures of the LM46-B, currently there are none on the net, that I know of, at the moment. If you wish, send me an EMail, and I will send you a photo. Keep an eye on EBay, one turns up occasionally. They are certainly an interesting item.:cool:

As to BWegher- nobody is perfect. I got my info from a gentleman who was in the small engine repair business for over 75 years. If the info is incorrect, please advise, and list the correct information, as K D Redd did. People here on the Stak would appreciate it. The 'AS Usual' is uncalled for, and not in keeping with the spirit nor the purpose of the Stak.:(

My personal experiance with the plug ends supplied by JC Whitney is as follows: They do light pretty brightly, but have a much higher resistance value than the LM46 B plugs. I tried to use them on a Honda 500 4 motorcycle, and they gave me fits in humid conditions. I also had a set on a model 72DA Maytag twin. Again, in humid conditions, sometimes I had hard starting. Otherwise, they worked well, but you had to be careful in handling them. The black end caps are brittle, and would break easily if they were rubbed up against. The ones sold by harbor freight also light nicely, and if you are careful, you can install it (the bulb assembly) on your own wiring.
Andrew:D
 

BWegher

Registered
Age
63
Re: B&S 5S - Intermitten Spark - Newbie Question

In modern Champion plugs, such as the J8C, the C after the heat range stands for Copper, not carbon.
 

K D Redd

In Memory Of
Re: B&S 5S - Intermitten Spark - Newbie Question

Andrew,

I thought the "As usual" was a bit sharp. If you know someone at an auto part store from whom you could get a last years Champion catalog. It will explain what all the prefix and suffix letters stand for. Such a J, H, N. These all denote a 14mm plug with differing tread lengths. One plug that Champion did not build a direct replacment for was the AC 44FF. Most people will not have a clue what engine this fits. It is for the air cooled flat 6 that was used in the Corvair. I know one guy who claims the Corvair engine was built by Franklin Airchraft Engines for GM. This plug reach extends 3/4 of an inch BUT only had 3/8 of an inch threaded on it. Champion used their "N" series plug in this app. the "N" series is a 14mm plug with 3/4 inch reach and is fully threaded.

Kent
 
G

Gauge

Guest
Re: B&S 5S - Intermitten Spark - Newbie Question

I feel the "As Usual" is not necessary as well. Andrew - I appreciate the info.

Well - I purchased a new condenser for my 5S, installed it, and now I have no spark at all! I am not sure what is happening here, but it is very discouraging. If I grab the wire and turn over the engine I get a nice ZAP, but if I attach it to the plug and ground it - no spark. The points look to be in great shape. The only thing left is the coil. Could the coil be bad? How can I test it?
 

John Newman Jr.

Subscriber
Age
64
Last Subscription Date
01/10/2019
Re: B&S 5S - Intermitten Spark - Newbie Question

Lets review "Flywheel Magneto Ignition - 101"

Condenser -
New

Points -
Polished & clean
Closing squarely
Insulators installed as necessary depending on style of points used*
Plunger moves freely in hole (but not sloppy)
Gapped to .020" at highest point of cam.

Primary Wires -
Check for worn insulation and/or breaks
Check for solid connections (look at all terminals)
No wires contacting ground

Armature -
Laminations not damaged (no layers of metal bent back)
No evidence of melting (globs of 'tar' oozing out)
Ground wire secured (bare wire under mounting bolt)
Plug wire connection secure (not soldered)
Ends of lamination legs clean (sand off any rust)
Gap to flywheel magnets .008" ~ .010" (thickness of a typical business card)

Flywheel -
Magnets have adequate strength (should hold a pr. of pliers)
Magnets are clean (sand off any rust)
New key

Sparkplug -
Gap set to .030"
Try a couple to eliminate possible bad plug (even if new)

* Book says:
"Install Breaker Points
To assemble, place the varnished insulator used with
the new style points beneath the point bracket.
The small boss on magneto plate should protrude
through the small hole in insulator and enter the hole
into the point bracket. If a small insulator is
fastened to the clip, the cambric insulator is
unnecessary.
Fasten the condenser and armature wires to the
breaker points with the clip and screw. The clip must
not touch the condenser, or the ends of the wires touch
the bracket as this will short the circuit.
Place armature wire and condenser wire under wire
terminal. Note position of wires, Install breaker point set on engine with cast boss in plate entering hole in point set."

These old Briggs mags are among the most reliable ever made. Most I have encountered needed little more than the points cleaned & gapped.

Hate to sound like a nag, but go over everything and then double check it again.
 

WVCS1958

Registered
Re: B&S 5S - Intermitten Spark - Newbie Question

Make sure you are actually grounding the plug to clean bare metal. If you are getting a "zap" from the plug wire you should have some spark. Try holding the end of the plug wire near a clean bare spot on the block or head and see if you get a spark there (hold onto the insulation of course). It's possible to have a new plug that's bad. If possible, try the suspect plug in another engine. I agree with John, most Briggs engines respond nicely to a simple points clean up unless some one has previously messed with them. Keep at it and good luck.
 
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