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Poor spark on Lucas SR1

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Poor spark on Lucas SR1

Post by Motorhead on Mon Nov 03 2014, 15:36

I have recently been having a bit of a struggle to get my Lister D to fire up. It doesn't get a lot of use but I try to get it going a few times a year to keep it alive.
I seem to be getting a pretty weak spark when turning it over with plug held to the engine metalwork. Probably even worse when it's struggling under compression. Can anyone suggest what I can do to improve matters?...........starting with the cheapest. A rewind is well beyond my means so not an option.
Thanks in advance.

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Re: Poor spark on Lucas SR1

Post by blue cat on Tue Nov 04 2014, 13:48

You can often find SR1 mags quite cheaply on the tat stalls at rallies if the Bakelite end cover is missing.
Take a multimeter with you to check the coil, you should get about 4000 ohms.

Sorry, as you live in France this reply may not be much help  Rolling Eyes

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Re: Poor spark on Lucas SR1

Post by Motorhead on Tue Nov 04 2014, 17:38

No help at all but thankyou for trying. The French would want more than the cost of a coil rewind for another S/H magneto. And the handful of rallies, etc. are too far away, etc. I was hoping for some input about what might be causing the weak spark. I will check the resistance of the coil as you suggest. I assume that is between the brass button under the bakelite cover to earth? Or is it to one or the other side of the points? I don't really have any sort of automotive engineering background so pretty much clueless when it comes to the basic operating theory. If the resistance checks out OK then maybe a condenser. An old one from a car might be OK if it physically fits the space.

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Re: Poor spark on Lucas SR1

Post by Motorhead on Wed Nov 05 2014, 15:40

Update. I was reading an article about renovating a Lister D and the author said to avoid painting the platform that the magneto sits on. There needs to be a good earthing connection from the body of the magneto to the engine metalwork. I decided to carefully lift the magneto and take a look underneath. The bolts were filthy with rust and muck and the surface under the magneto had about three coats of paint on it! I took a sanding disc to that lot and cleaned up the bolts as well as I could. The magneto provides a much better spark now and the engine runs sweet.

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Re: Poor spark on Lucas SR1

Post by StewartH on Thu Nov 06 2014, 14:53

Tres Bien! It never takes long to find a solution or advice online!

enjoy your engine running better!

Hamish

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Re: Poor spark on Lucas SR1

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