Joined: Mar 2015 Posts: 5,436 Threads: 231
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Location: Scotchland
I have resurrected the Sevens after more than a year and a few niggles (I had forgotten about), have raised their heads.
The BLIC magneto on the Chummy has performed faultlessly for 11 years but has developed a slight miss fire when I advance it more than half way on the controls, it is almost as though it is shorting out out on something as the assembly rotates.
I have been told this is a common fault with BLIC - does anyone have experience of this and a cure please?
Joined: Aug 2017 Posts: 502 Threads: 13
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Could this be the condenser Ruairidh ?
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A good site to read is The Magneto Guys.The Evxo Rifa PME271M capacitors are not sold by The Magneto Guys,but can be found on ebay , but watch out for poor quality ones.
Over the years in my work I have replaced thousands of capacitors (condensers) and found poor quality ones are a waste of time and money.
The same type of capacitors can be used in DJ & DK distributors but check the value , these are 0.22mfd.
Joined: Aug 2017 Posts: 881 Threads: 48
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Location: North Wiltshire
Car type: 1927 Chummy, 1938 Big Seven 1/2 a Trials Chummy
If I remember correctly, the HT voltage increases when the magneto is advanced (I can't remember exactly why) and the miss-fire can be a sign that the insulation on the coil is beginning to fail.
You will remember the 1989 BA7C alpine holiday Ruairidh? I had exactly this problem on the way down to the alps, the magneto (a BTH) failed a few days later. It was replaced by my SR4 Tractor mag; these never miss a beat and I heartily recommend them.
Joined: Aug 2017 Posts: 914 Threads: 22
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Location: Near Cambridge, UK
Car type: 1928 tourer (mag type), short chassis Gould Ulster
22-03-2021, 12:16 PM
(This post was last modified: 22-03-2021, 12:17 PM by Robert Leigh.
Edit Reason: further comment
)
Parazine is right. On one occasion I reached Leominster on my way to the VSCC Welsh with time in hand, so stopped for a cup of tea. After that the trouble started. Side of the road investigation sounded like sparks under the cover on the BLIC. By holding the mag in place without the cover all was well, so I broke a substantial twig from the hedge to use under the fixing strap instead of the aluminium cover. Unfortunately we reached Presteigne just outside our latest arrival time, but we still got a 'First' class award on the rally the next day. At least changing the coil on a BLIC is just about the easiest you will find.
Joined: Mar 2015 Posts: 5,436 Threads: 231
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Location: Scotchland
Thanks Tim,
my strongest memory from that holiday was an issue you had with your clutch release bearing, involving some pretty hairy start-offs in traffic!
Love a "twig" story Bob!
Joined: Mar 2015 Posts: 5,436 Threads: 231
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Location: Scotchland
To complete this for future reference of others.
Robert Foreman very kindly sent me some new condensers - one of which I fitted. This made no difference, unfortunately.
Stuart Ulph suggested a chaffed wire from the coil - this was checked and found to be fine.
Robert spoke with me and suggested the points - bingo! The pin that holds them had worked loose and was wobbling. Tightening this, along with some thorough cleaning of the points themselves, has cured the problem entirely.
Thank you for everyone's help, Forum at it's best once more.
