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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
BTH magnetos
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<blockquote data-quote="peterg" data-source="post: 12152" data-attributes="member: 446"><p>Howdy Sir,</p><p> </p><p>Yes it likely does and probably explains no response to this post. The absense of any "confusion" surrounding a BTH install occassionally afflicting other retrofits wherein the successful few toss out regular/glowing praise to encourage others encountering problems mid-project to soldier on, results in little fanfare with these, defensive or otherwise. They just plain work, no generator/alternator required.</p><p> </p><p>In my case, A BTH was at the head of the short list of tasks on the Red Rap in preparation for the VOC NA Rally in 2 weeks. I fitted this one last night. Why would one replace a perfectly good rebuilt Lucas and ATD after only 5k miles? When measured against the 1,200 miles aboard my Shadow after fitting a BTH in 1/09 it was a no brainer. The shortcomings of the Lucas mag design are well documented, innacurate cam ring machining requiring splitting advance between pots, etc.. so won't dwell on that. But, will say I'll take CD ignition any time available when a reliable spark is required in an overly fuel rich environment as typically seen with our Vin's and as Porsche discovered in 1968 with the fitment of Bosch MFI. The U.S. sourced Permatune CD box was the only solution, and a variation remained available pretty much up until the 964.</p><p> </p><p>But, the real culprit here in seemless performance and even a predictable idle is the ATD. Like Vin shocks, a laudible exercise into the unknown then for which substantial evolution has only made its shortcomings more apparent now. Whereas most advance mechanisms must only adjust the mass of a short distributor shaft back/forth, this device must overcome the sustained load of a generator and control the mass of the armature on overun, with minimal leverage and small springs. Unless absolutely perfect, one can feel stepped feeding of advance on steady acceleration, and a blip of the throttle can be required to sling the weights so a little more momentary spring tension can snap the device back to retard. Speaking of springs, like /2 BMW's one has no idea what the advance curve has become between full retard and full advance settings when fitting non-original springs. As a BTH actually is set at full advance, and pulls timing out the lower the rev's , I have no idea if that analog map is ideal at every rpm setting but it is academic anyway - too many compression ratio's, cams, carb options for BTH to possible address for an over the counter solution - but what's delivered here is smooth and perfectly repeatable every time/over time. </p><p> </p><p>I have no idea what fails on a BTH, a stockist here has spare coils, but short of ruining them with a torrent of water spray off the front wheel or suppressing them with too much resistance, don't know that they'd even be regarded as a noteworthy liability. Even if they only lasted 10k miles, it wouldn't be a problem, the blissfull 9,999 in between would have certainly cemented most one's affections for this device.</p></blockquote><p></p>
[QUOTE="peterg, post: 12152, member: 446"] Howdy Sir, Yes it likely does and probably explains no response to this post. The absense of any "confusion" surrounding a BTH install occassionally afflicting other retrofits wherein the successful few toss out regular/glowing praise to encourage others encountering problems mid-project to soldier on, results in little fanfare with these, defensive or otherwise. They just plain work, no generator/alternator required. In my case, A BTH was at the head of the short list of tasks on the Red Rap in preparation for the VOC NA Rally in 2 weeks. I fitted this one last night. Why would one replace a perfectly good rebuilt Lucas and ATD after only 5k miles? When measured against the 1,200 miles aboard my Shadow after fitting a BTH in 1/09 it was a no brainer. The shortcomings of the Lucas mag design are well documented, innacurate cam ring machining requiring splitting advance between pots, etc.. so won't dwell on that. But, will say I'll take CD ignition any time available when a reliable spark is required in an overly fuel rich environment as typically seen with our Vin's and as Porsche discovered in 1968 with the fitment of Bosch MFI. The U.S. sourced Permatune CD box was the only solution, and a variation remained available pretty much up until the 964. But, the real culprit here in seemless performance and even a predictable idle is the ATD. Like Vin shocks, a laudible exercise into the unknown then for which substantial evolution has only made its shortcomings more apparent now. Whereas most advance mechanisms must only adjust the mass of a short distributor shaft back/forth, this device must overcome the sustained load of a generator and control the mass of the armature on overun, with minimal leverage and small springs. Unless absolutely perfect, one can feel stepped feeding of advance on steady acceleration, and a blip of the throttle can be required to sling the weights so a little more momentary spring tension can snap the device back to retard. Speaking of springs, like /2 BMW's one has no idea what the advance curve has become between full retard and full advance settings when fitting non-original springs. As a BTH actually is set at full advance, and pulls timing out the lower the rev's , I have no idea if that analog map is ideal at every rpm setting but it is academic anyway - too many compression ratio's, cams, carb options for BTH to possible address for an over the counter solution - but what's delivered here is smooth and perfectly repeatable every time/over time. I have no idea what fails on a BTH, a stockist here has spare coils, but short of ruining them with a torrent of water spray off the front wheel or suppressing them with too much resistance, don't know that they'd even be regarded as a noteworthy liability. Even if they only lasted 10k miles, it wouldn't be a problem, the blissfull 9,999 in between would have certainly cemented most one's affections for this device. [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
BTH magnetos
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