lister d rs1 mag intermittent spark

ive been round my granparents retired farm alot recently and we have two old lister d engines and a petter a1 none of which run in at the very minimum 30 years weve tried to get one of the lister ds to to run it ran for a few seconds but not very well then cut out ive tried checking the spark but it was intermittent hence protably why it ran rough then stopped so does anyone know how to fix intermittent spark on a lister d rs1 mag

Hi, you will probably need to start  checking the points are clean, they furr up with an oxide coating if left for long periods , also a resistance check on the coil if you have a multi meter, set to 20000 ohms and you should get a reading of between 5000-8000, its been a while so I hope I have that correct,  

Good luck
Chris

ive already cleaned and gapped the points but ill have to check the coil over thanks Austin

Hi and welcome to the forum. Let me know if you need manuals.
Good luck.

hello ive managed to get hold of a multi-meter witch ends does toe positive and negative go on. positive on the side inputting the condenser and negative on the piece on top contacting the wire running to the spark plug

take the cap off and make sure the coil pickup is clean as well as the pickup attached to the cap, rif you cant check the capacitor with the meter, some meters can check them, replace that as it maybe breaking down.
Finally if all else is ok remove the magneto and check the mag base and the place it sits on for corrosion or crud.
Maryalice