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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
New style BT-H mag
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<blockquote data-quote="Simon Dinsdale" data-source="post: 35613" data-attributes="member: 58"><p>Hi Craig,</p><p></p><p>After discussions with the original owner of BTH (now under new ownership) he said that the only common component to both cylinders is the rotational drive and the internal generator. The two cylinders have seperate pickups and electronics.</p><p></p><p>Now at work I have the capability of measuring high voltage pulses. I looked at the output of both coils at 200rpm shaft speed which is the equivalent of 400 rpm crank speed which is approx what the kickstart speed is. At this speed there was no output at the coils. Had to spin the BTH at 500 rpm to get a output that would break down a spark plug. That is 1000 rpm crank speed. Way to high for kickstart and was confirmed by the bike would only start when bumpstarting. Tried this with the spare coils I had and got the same result, so it was not the coils as sugested at the time. </p><p></p><p>Now this is a unit that when I first got it would start the bike with the slightest of kicks, and as the failure was occuring on both cylinders the conclusion was the failure must be in the only common part of the BTH to both cylinders - the internal generator. Now I don't know how the internal generator works as I have not dismantled the unit that far. When I discussed this with Tony at BTH he sort of agreeded with my conclusion but would want to look at the unit (at a cost). I have got to admit with the bike running great on std coil ignition, the BTH unit has been put in the back of the garage and not looked at since. To me reliability is everything as I do travel a lot on the bike and so even if it was fixed I don't think I could trust it again.</p><p></p><p>Just realised Craig yours is a Comet. So you won't be able to use the conclusion of "the only common part of the BTH to both cylinders". Now if I had seen a difference between the outputs of both coils (was a unit for a Rapide) I would have concluded that a electronic CDI unit for that faulty cylinder was the problem after eliminating the coil and HT leads etc.</p></blockquote><p></p>
[QUOTE="Simon Dinsdale, post: 35613, member: 58"] Hi Craig, After discussions with the original owner of BTH (now under new ownership) he said that the only common component to both cylinders is the rotational drive and the internal generator. The two cylinders have seperate pickups and electronics. Now at work I have the capability of measuring high voltage pulses. I looked at the output of both coils at 200rpm shaft speed which is the equivalent of 400 rpm crank speed which is approx what the kickstart speed is. At this speed there was no output at the coils. Had to spin the BTH at 500 rpm to get a output that would break down a spark plug. That is 1000 rpm crank speed. Way to high for kickstart and was confirmed by the bike would only start when bumpstarting. Tried this with the spare coils I had and got the same result, so it was not the coils as sugested at the time. Now this is a unit that when I first got it would start the bike with the slightest of kicks, and as the failure was occuring on both cylinders the conclusion was the failure must be in the only common part of the BTH to both cylinders - the internal generator. Now I don't know how the internal generator works as I have not dismantled the unit that far. When I discussed this with Tony at BTH he sort of agreeded with my conclusion but would want to look at the unit (at a cost). I have got to admit with the bike running great on std coil ignition, the BTH unit has been put in the back of the garage and not looked at since. To me reliability is everything as I do travel a lot on the bike and so even if it was fixed I don't think I could trust it again. Just realised Craig yours is a Comet. So you won't be able to use the conclusion of "the only common part of the BTH to both cylinders". Now if I had seen a difference between the outputs of both coils (was a unit for a Rapide) I would have concluded that a electronic CDI unit for that faulty cylinder was the problem after eliminating the coil and HT leads etc. [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
New style BT-H mag
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