The Old Lawnmower Club
Collection, Preservation and Display of Old Lawn Mowers

Webb AB 1439 no spark at plug

Enter a word or two to search the forum section and click the Search Forum button.
Paulblack

Hi, I have recently retired and have decided to refurbish my old Webb AB 1439 24" cylinder Mower, It is fitted with a Briggs and Straton 5HP 4 stroke Engine Model No 130202, Type 0842 01 Code 79120407.  before I start to dismantle it for overhaul, I thought it good practice to make sure she runs first, to cut a long story short I have found that the magneto is not supplying a spark at the spark plug ! I have checked the cut out switch all OK, the wiring from the cut out goes into the casing behind the flywheel ? would this go to an oil level switch which is normally open circuit ? the core comes out of the casing to one side of the magneto coil and the other side of the coil is earthed ?

I have checked continuity from cut out switch all ok ?

Any help on the wiring circuit diagram and advice on where to purchase a new Magento coil would be very much appreciated

Best Regards

Paul  

Forums

Mowing Wurzel Thu, 11/06/2026

Hello,

The 5hp engine was popular in its day,  190 denotes the model, and the 202 gives the variations. i.e. plain bearings, etc    This engine was popular on the Wolseley Titan cultivators. 

As your machine is a 1979 build (assuming engine to be original as the serial numbers are on the cover) 

 it would have contact breaker points behind the flywheel, unless retro-fitted.  It was in the early 80's that B&S brought out their Magnetron  system that made it simple without points.  Obviously for 40 years you just have the two prong coil on the top of the flywheel where the high tension lead goes straight to the spark plug, and a small wire for cut off.

There wouldn't be a low oil switch on these, as these came in slightly later.

 Engine Model No 130202, Type 0842 01 Code 79120407. 

 magneto is not supplying a spark at the spark plug ! I have checked the cut out switch all OK, the wiring from the cut out goes into the casing behind the flywheel ? 

would this go to an oil level switch which is normally open circuit ? the core comes out of the casing to one side of the magneto coil and the other side of the coil is earthed ?

I have checked continuity from cut out switch all ok ?

Any help on the wiring circuit diagram and advice on where to purchase a new Magento coil would be very much appreciated

Mowing Wurzel Thu, 11/06/2026

So the reason you have no spark is that the  contact breaker points are corroded on the faces, this can be a simple fix if it is just cleaning the platinum faces,  I'm sure there must be a good video on youtube which shows this.

if not I can photocopy a page out the book. (photo below)

The other thing is the condenser, the steel canister next to the contact breaker points, this stores the high tension charge which is released on the points making contact every rotation.

I hope this hasn't led to more questions.