Misc: Ignition BTH Magneto sparks erratically...

Rixon

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VOC Member
I looked at the Grosset ignition but was surprised to find that it retains the old ATD unit for advance. I would have expected a modern ignition system to have electronic advance curves.
 

Marcus Bowden

VOC Hon. Overseas Representative
VOC Member
It's the KISS system "keeping it simple stupid"have one on daughters rap since 2000 and on my "B"rap 2006 extremely low consumption even twin plugging easy to time with red LED to go by. Happy customer.
bananaman
 

stu spalding

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Has anyone ever checked magneto v points/coil v electronic ignition on a dyno? It would be interesting to see what, if any, difference in horsepower is involved, or is the leap to electronic simply because it's the latest thing? Cheers, Stu.
 

Peter Holmes

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I think the whole automotive industry embraced electronic ignition because it is better, feeler gauges and cigarette paper are a bit archaic, but I still use them on some of my bikes, the BTH electronic is on the other bike and that works very well, in the past I have blamed it for various maladies, but it has normally turned out to be fuel related, with one exception when the coils packed up whilst on the Isle of Man
 
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Rixon

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VOC Member
I doubt there's a lot wrong with a well set up points system on a low revving engine. On the other hand I would doubt that any two ATD's would give the same results if compared on a test rig.

My only experience is on cars where I have had rebuilt, and new, distributors tested on a rig. Since then I've used an electronic distributor !
 

timetraveller

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Magneto man would provide a better answer than me but here is my experience. Every magneto I have ever used would produce a spark, perhaps 1/4" long at the most. When I first bought the ex-Cecil Mills production class racer it had a 6 volt coil ignition system. Cecil had told me years before that he had had a special coil built but it looked like a standard coil from the outside. On one occasion while checking something I had the output from the coil to the distributor disconnected and while turning the engine over a spark came out of the coil and went to earth about 2.5" - 3" away on the crank case. It would do this repeatedly if I kept turning the engine over. I can well believe that the magneto would give a better spark at higher rotational speeds and the coil, at any normal engine revs, never seemed to have a weaker spark. The method for checking this is a simple adjustable gap that was bought many years ago as a cheap tuning aid. Roughly at the same time as I bought a colour tune glass spark plug. I have never tested a new BTH magneto. Whether the length of a spark is sufficient information to characterise the power of a spark is open to discussion.
 

greg brillus

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For racing it depends a bit on what fuel you are running. Electronic set ups seem ok for racing, but because of the complexity compared to a magneto, they seem to easily suffer issues that can be difficult to trace. A magneto is better in my opinion for alcohol fuels as a magneto has less voltage but more current, and this is a big plus for igniting cold fuels...........Hence this is why top fuel dragsters use very powerful magnetos for their ignition. They put out 44 amps plus............
 

vibrac

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VOC Member
You would be lucky to see a BTH spark I know when mine was on the test rig I could not see the spark but I could not miss the holes it punched/burnt through the fag paper when stuck between the plug gap
 
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