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Collection, Preservation and Display of Old Lawn Mowers

Converting B&S from points / condenser to electronic ignition

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Dear reader,

We just started on the Webb AB1476. It has no spark. The spark plug has been changed, points have been cleaned to no avail. Now we have some options left:

Now, I also had the idea to replace the whole old ignition with a new electronic one. Such a swap can be seen numerous times on Youtube, although usually with a bit larger engines then the 60102 we have here (3.5HP and 5 HP are very similar), what I could see that this could be achieved with: https://www.japgmowers.co.uk/ignition-coil-armature-magneto-briggs-and-…

Now Japg tell me that this can't be done, why? Do you have an idea?

 

Forums

wristpin Mon, 04/11/2019

I suspect that the centre to center measurement for the holes in the coil armature mounting pillars on the block may be different. There are some BS armatures that look very similar but that measurement is slightly different. *

A rare but not unheard of issue is that the fibre breaker plunger is sticking in its bore and not allowing the points to close completely.

Can you not get the coil and condenser tested?

* I've got a 5hp block out in the shed and I'll take that measurement later, but there's a lot of stuff in front of it so probably not until the morning. ** torch in one hand, vernier in the other 60mm !

EDIT just looked at your link . It says out of stock and also looking at their comprehensive list of what it fits there is no mention of a 13 series (5hp) engine so it suggests that a 5Hp wont fit yours. 

Henno Tue, 05/11/2019

Good points that you added. How to test a condenser and coil? At a garage? Those outfits only throw stuff away these days... Regarding the item on JAPG's site, the 60102 that we have (2HP) is mentioned in compatible engines..

wristpin Tue, 05/11/2019

Possibly a workshop dealing with vintage motor cycles will have proper coil and condenser testing equipment. Mower shops over here would have in the past but now ......... !

I may have misunderstood your original post as suggesting that a 5hp coil might be compatible with yours  - I believe, not due to a difference in the armature fixing hole spacing but I only have a 5hp to measure.

wristpin Tue, 05/11/2019

Basically that’s a static test for the primary and secondary coil resistance but it doesn’t necessarily mean that it will work in a dynamic situation. The only thing that you can 100% rely on with a static test is if either coil shows an open circuit, that is no change at all of the meter reading between the probes being  disconnected and hooked up to either coil.

A proper coil test stresses the coils in a similar way to a running engine, a multimeter will not. Similarly one can do a static test on a condenser , preferably with an analogue multimeter, but again it is not a real life test. In a dynamic condenser test the tester will attempt to charge the condenser. If it is good it will charge and do no more. If not good the tester will continue to try to get it to accept the charge. Once the charge is accepted the condenser should retain it for at least ten seconds. If the charge leaks away within ten seconds the condenser will fail in a running situation. 

Magnetron coils . While it is possible to statically test these with a specific tester that can simulate the rotating flywheel to trigger the spark, Briggs have always said that the practical test is whether the coil produces enough energy to spark over a quarter inch gap from the end of a bare HT lead.

Henno Tue, 05/11/2019

Thanks for the thorough explanation. We haven't done a passive check if the coil is a open or short, will do that first, then decide what next step to take.