The title is only half the story, the coils are hot as well !
The way this has been set up has lasted five years, so why is it playing up now ?
What I have is a Boyer ignition unit wired to two Jap coils which are bolted with their own integral bolts to the frame of the Wasp. There are two leads per coil but of completely random colours, however I made a calculated assertion and connected the Boyer just as I would on a Commando, black lead to first coil, then neg off that one to pos on other then neg off second one to earth. As I said its worked for several years, but today after a long time unused I tried to start it. At first it ran,but badly, so cleaned out carbs, then tried to restart and it just backfired loudly and noticed that both Boyer and coils were very hot. The Boyer blurb says that the black wire must have earthed, but I fail to see where as it goes straight to the first coil.
Can anyone enlighten me as to which lead is + and which - on these coils, OR is that not the problem.
Thanks in anticipation
HT
I guess that the coils are…
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Hi Hans, Check all the ass…
Hi Hans,
Check all the associated connetions in that circuit, including the earth returns, plug cap connetions etc. anywhere in the line from from the battery - through the coils -back to the battery can cause voltage drop / high current flow which you just maybe noticing at the coils as these are the bits that 'do' something and thus the poor running.
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Hi, If things are getting…
Hi,
If things are getting hot then it is LOW resistance not high, the resistance according to Boyer should be between 3 and 7 ohms, have you measured yours ? are both coils the same ?
I know on the standard aly coils it is possible to over tighten the clamp and short out the windings. If one coil goes very low resistance the other coil will get more voltage and will also get hot.
You could simply try putting a voltmeter across the coils with the ignition on, you should see the same voltage across both. (about 6v)
It does not make a great deal of difference which way you connect the coils but if you have positive earth then if the coils have a +ve and -ve marked on them then then you should go - Boyer to first coil -ve, link from first coil +ve to second coil -ve, second coil +ve to ground. If it is the wrong way around it can make your spark plugs wear a little quicker (I can explain if required).
Regards
Tony
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I had an overheating Boyer…
I had an overheating Boyer on a twin spark B44, dual coil resistance was 2.9 ohms, fitted 2 single coils in series each 1.7 ohms giving 3.4 ohms total and no more overheating Boyer.
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I guess that the coils are a higher resistance than ideal for the boyer, this will draw more current and get hot like any resistance. The increased current flowing through the Boyer box will heat that up as well. Just buy two new coils of the recommended resistance and all your problems will probably disappear, hopefully not in a cloud of smoke.