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Design improvements for the BT-H?

minivin

Well Known and Active Forum Website User
VOC Member
Morning Gents and Ladies,

I have been thinking on a few problems on the BT-H over the past few weeks and now I have solved the problem of starting the bike, I thought I would note some issues I have come across and wondered whether anyone else has found any undesirable design issues?

First problem I had with the twin spark variant for a Comet was that the extension for the coil mountings, meant that the outer ignition coil was fitted "through" the magneto cowl. Picture of mounting tab below:



I then cut-down the tab to that which I believe is the standard size for a single spark model and refitted the inner coil and confirmed the magneto cowl now fitted:



Using some stainless sheet I have in the workshop, I made an "L" tab of 3/4" x 3/4" (or there abouts, I didn't make any notes) and fitted the second coil to the front of the BT-H and this now allowed the magneto cowl to fit:



I did have to extend the wires to the second coil, I also had to fit flag terminals to the wires to prevent the wires chaffing the spring and mechanism of the prop stands.
 
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minivin

Well Known and Active Forum Website User
VOC Member
Another problem I am not happy about, is that the mounting flange is much thicker than the mounting studs allow. The nuts and studs not being in "safety" (which in general in aerospace terms is "one and a half" threads protruding through the nut) is unacceptable. Either longer studs should be supplied, or the flange reducing in thickness to allow the nuts to be in safety. I used Loctite 270 to help guarantee the fasteners staying tight, but anyone else who does not do this could have their magneto fall off:




Finally for me, I am not happy with how the wiring loom exits the body of the magneto. It exits against one of the crankcase mounting stud bosses which over time runs the risk of the loom chaffing through and shorting-out:



I believe the exit hole needs moving to the bottom of the body (for moisture reasons this would also be a wise solution.


Does anyone else have any issues before I contact BT-H?
 

greg brillus

Well Known and Active Forum Website User
VOC Member
I believe the case and cover should have "O" ring grooves installed to help seal the unit from moisture ingress, after all there is no points assembly and so on, so why should the unit have to "Breath" as it were. It has been an issue with some of these mags that are used by owners who ride in all types of weather, and upon cooling down, draw in moisture which starts the internals to corrode away nicely causing isses......there have been problems with the HT coils to, but they may have addressed that one. Also I think the mounting strap could be a bit better, as most who have installed these units know...there isn't much room to keep it all behind the cowl, and also keep it clear of the prop stand springs.....the plastic insullated HT lead melts upon contact with the barrel/ head fins, a silicone type outer insulation would help here......should I stop now....!! Generally I have found them to be a good unit.....but some have had issues....Greg.
 

vibrac

Well Known and Active Forum Website User
VOC Member
Wow! some one who puts BTH coils under the cowl. up, up, find a corner in the space under the tank.
 

1660bob

Well Known and Active Forum Website User
VOC Member
Yes I too had to do some final fitting to accomodate the BTH and coils. I think its fair to say that offering up the unit to an engine is really only the start point.All crankcases will differ in generosity of casting to some degree, and mine was a good example. I found that to get the BTH to sit down PROPERLY on its mount/sealing face took some careful work with a file/torchlight etc.I had to relieve the corner of the nearside crankcase half at the joint line as it protruded forward a lot here as compared to the other case half. I then found that the BTH itself had signs of metal removal at the back (from new), where they are closest to(interfering with ?) the engine cases. I found it necessary to remove more to ensure comfortable clearence at the back.I then found that the rear, lower "point" on the BTH triangular mounting flange was also too generous, and overshot the machined flat on the engine case,preventing it from sitting down and necessitating considerable metal removal with a file (on the BTH) This done, I satisfied myself that the unit was fully sat down, flange to case AND with sufficient clearence to allow full "swiwel" on the timing adjustment slots.Time and care is needed, much peering underneath with that torch to achieve a proper result. I suspect many could be badly fitted and whacked up tight on the nuts causing stress/misalignment/oil weeps etc etc.
Its also worth noting that the supplied long "screwdriver" type allen key really, in my opinion needs to be ground right down along its shaft,rounding off the hexagon profile and reducing the overall dia., so that it fits easily behind the unit when tightening the bolts- and the corners of the said hexagon shaft , once removed, do not damage the wires where they emerge from the unit, which is pretty much in line with where the allen key needs to be! Yes ,I agree, a wiring exit at the bottom would be much better.

Moving on to the coils, again, work is likely needed to mount them as each owner prefers- its more of a personal preference thing here, space is tight, and all needs to be kept well tucked in away from the stand springs etc.I modded my bracket to pull everything in tight and "point" the coil lead ports towards the cowling exit nicely. I had to cut and extend the LT vin bth mag inst. 002.jpgvin bth mag inst. 006.jpgvin bth mag inst. 003.jpgvin bth mag inst. 004.jpgvin bth mag inst. 005.jpgwires, and I also found that "flag" type connectors are better here for neatness and clearence-here`s my effort, all fits nicely under the cowl with no rubbing /clearence issues. Regards,Bob.
 

BigEd

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VOC Member
VOC Forum Website Moderator
A few observations regarding fitting the new BT-H to a Vincent.

  1. Some engines had very "full" castings and required a bit of judicious easing.
  2. The stainless bracket for the coils allowed the owner/mechanic to twist, bend, cut, etc to get the fit he or she required. On virtually every Vincent installation I've seen they have been a little different. (We Vincent owners like to put our own little touches on a bike.;-))
  3. Not sure about the thickness of the flange. The studs on mine, I agree, are barely long enough but it it hasn't come loose in the 4 or 5 years and thousands of miles of use and abuse since I fitted it.
  4. To keep costs down one casting was used to fit as many different makes as possible. The shape does allow the use of the long nut rear nut on a Vincent without producing a different casting and the related extra production cost. The Allen head bolt and long Allen key supplied allows the same casting to fit a Vincent. Design is sometimes a compromise between ideal and affordable. (Having said that there may be something new on the horizon that visitors may see at the Stafford Show later this month.)
  5. The way the wires exit the body is not ideal but it is workable. The reason is probably as per "4."
  6. The routing of any wires should be checked before bolting on the cowl. Also see note on BT-H website here. http://www.bt-h.biz/coil_clearance.htm
  7. I use the standard supplied HT leads and have never had anything melt.

As always your experience may differ.:)
 
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Vincent Brake

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VOC Member
The only improvment i made was put on a Pazon, it works like a marvle. (and spare battery of course, nowadays Lithium are light weight)

Been out yesterday
 

BigEd

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VOC Member
VOC Forum Website Moderator
My battery died yesterday :( but fortunately the magneto is not reliant on a battery.

If you choose to use a fully electronic system I am told that the Pazon battery powered system is not so susceptible to low battery voltage as the Boyer system where low battery can result in a spark without automatic retard for starting.
 

Howard

Well Known and Active Forum Website User
VOC Member
If you choose to use a fully electronic system I am told that the Pazon battery powered system is not so susceptible to low battery voltage as the Boyer system where low battery can result in a spark without automatic retard for starting.[/QUOTE]

This is the Norton Commando owner's favourite, and the problem will probably be relevant to Vin owners with electric start. Apparently, pressing the start button can create a big battery voltage drop which sets the ignition to fully advanced, the kick back then damages the starter motor. H
 
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