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BTH Magneto pinion

redbloke1956

Well Known and Active Forum Website User
Non-VOC Member
Hi all, I have just purchased a BTH magneto for the Comet, can anyone tell me if I need to buy a new pinion for the BTH or can I somehow remove (I assume by removing rivets?)the ATD and use the existing pinion.
Thanks
Kevin
p.s. can anyone tell me where to get the oil seals that are in the timing chest (the ones that make contact with the oil carrying spindles)
I cannot find them in the Parts Lists
 

john998

Well Known and Active Forum Website User
VOC Member
Hello,
I would buy a new pinion, and keep the ATD as a spare.
The oil seals are ET183 drawing OM32 and should be available from the spares company.
Would love to visit OZ again, so please try to get the value of you currency down for me.
Regards John.
 

Howard

Well Known and Active Forum Website User
VOC Member
I agree with John, but I have seen one with the weights and springs removed and the inner and outer moving bits tack welded together - bit of a bodge, but a quick fix.

H
 

Simon Dinsdale

VOC Machine Registrar
VOC Member
VOC Forum Website Moderator
From listening to conversations at a recent rally, the best thing would be to get the original Lucas professionally rebuilt, and fit a new ATD from Roy Price, or fit coil ignition with series D type distributor. Will be more reliable than a new BTH of which several people have had fail.
 

davidd

Well Known and Active Forum Website User
VOC Member
I think it is worth the effort to build up a new pinion for the BTH you have just purchased. I have been running one for several years. Here is a photo of the items you may need. I have written in the numbers for the ring with no dog for the tach and Russel at VinParts has one listed with a /1 on the end. I do not know what it is, but I noted it just in case. So, you need the back and front of the mounting (that traps the self extracting nut), the self extracting nut and the hardware to hold it together.

TachDriveInfo0001.jpg


David
 

A-BCD

Well Known and Active Forum Website User
VOC Member
I didn't want to disturb the timing cover, so I removed the ATD springs and made a simple plate to lock it in the full advance position. Then you can fit and time the BT-H, job done. The ATD can always be used if you switch back to a Lucas mag.
Easy peasy !!
atdplate.jpg
 

davidd

Well Known and Active Forum Website User
VOC Member
I take the timing cover off so often I made a tool to pop it off so I do not have to whack it! Yes, it uses the Vincent taper.

I would also note that on mine timing it acurately is a little tricky. I assumed the spark occurred when the 6mm rod could be inserted through the armature, but by marking my engine pully and strobing it I found it was five degrees away from the number I set it to. I found that there is about 5 degrees of rock on either side when the rod is inserted. It turned out that the spark happens when the backlash is taken out rotating the rear wheel in the direction of travel. So I now set it at 24 degrees and when the play is taken up it is firing at 19 where I want it, as an example. I do not know if this is unique to mine.

David
 

BigEd

Well Known and Active Forum Website User
VOC Member
VOC Forum Website Moderator
David has raised some good points here. The BT-H peg locks the magneto shaft in the firing position when the pinion is pushed onto the taper. With any train of gears/sprockets you will get backlash so this needs to be taken up in the appropriate direction. Checking by a strobe is usually problematic on a Vincent but probably the best way to check your real ignition timing whatever ignition system you use. The new BT-H does have slotted holes so that you can experiment a little with the timing by slacking the fixings a little and rotating the mag. Easier than breaking the taper and starting again.:) With the engine running I rotate the mag till the strobe shows the timing I want.

The VOC Spares Company list a magneto pinion kit for the BT-H magneto. That is what I have fitted to my Rapide. The kit doesn't contain the bits to drive a rev-counter if you want to fit one so you need to source those parts separately.

u have on fitted so
I take the timing cover off so often I made a tool to pop it off so I do not have to whack it! Yes, it uses the Vincent taper.

I would also note that on mine timing it acurately is a little tricky. I assumed the spark occurred when the 6mm rod could be inserted through the armature, but by marking my engine pully and strobing it I found it was five degrees away from the number I set it to. I found that there is about 5 degrees of rock on either side when the rod is inserted. It turned out that the spark happens when the backlash is taken out rotating the rear wheel in the direction of travel. So I now set it at 24 degrees and when the play is taken up it is firing at 19 where I want it, as an example. I do not know if this is unique to mine.

David
 
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