Fitting BT-H Magneto

[redbloke1956]

Hi Kevin,
I haven’t taken much notice of this thread, because I know nowt about BT-H. I’ve just had a quick scan, so I may be going over old ground, but have you checked the diameter of the tapers. A small difference in diameter will make a relatively big difference to the position along the shaft.
I know it’s a pain in the bum, but If I’d spent that much on new parts, I wouldn’t be settling for incorrect meshing pinions!

H

G'day Howard, I understand your reasoning and the concept is perfect except that I would need a datum as a starting size to enable me to tell if one is too large or one is too small (with respect to the datum).
Thanks for the input mate. (you wouldn't have a datum in your box of bits would you?)

Kevin

 

[BigEd]

Dear Kevin,
Just a thought. When I looked back through your earlier posts you said:
"One interesting point though...I have noticed that the original ATD has had the taper resleeved at some point....there is no (or little) internal taper"
I wonder why this was done? Could it have been done to correct an assembly mistake?

Is it too daft a question to ask or is it possible that the train of gears was incorrectly shimmed out too far?

 

[nkt267]

Time to jump in with both big feet.
Could it be possible that the Spares co may have been supplied with the wrong parts?. If the same mag fits a Velo( I suspect it is the same physically), could the taper boss be the incorrect one? Try to get the spares Co to take photo's of another fitting kit to see if it is the same as yours or Email BTH for some dimensions of the adapters, if they supply them..John

 

[Howard]

G'day Howard, I understand your reasoning and the concept is perfect except that I would need a datum as a starting size to enable me to tell if one is too large or one is too small (with respect to the datum).
Thanks for the input mate. (you wouldn't have a datum in your box of bits would you?)

Kevin

G'day Kevin.
From the wide and various selection of ignition parts in my spares cupboard (actually worn out but I don't like throwing things away).

The shaft taper is 11 mm minimum diameter (yes it really does seem to be in mm) and 13 mm max diameter NB at 11 mm from the minimum diameter end. Mag shafts seem to have a longer taper than my coil ignition setup, but they all seem to got from 11 to 13 over an 11 mm length. The 11 mm dia is 14.2 mm from the face of the mounting flange (not the spigot). the spigot is 2.7 mm thick, so the 11 mm dia is 11.5 mm from the spigot face.

The max bore on the ATD is 13 mm - I can't measure the min dia, or length of taper, but since its a snug fit on the shaft it should be the same dimensions.

When the ATDs fitted the distance between the mounting flange and the pinion face is 14.2 mm.

Hope that makes sense. Good luck.

H

ps it's not easy to measure a diameter on a taper with my measuring kit, so my measurements are only for starters.

 

[b'knighted]

Now you've let me down Howard. I expected you say that you hadn't got a datum but had got a calendar.

 

[Howard]

Now you've let me down Howard. I expected you say that you hadn't got a datum but had got a calendar.

Sorry I'd just got home from a club run, when I follow Richard Kettle on his favourite roads, I have to leave my brain in the toolbox!!

Anyway,............. shouldn't that be Calendum?

H

 

[redbloke1956]

Time to jump in with both big feet.
Could it be possible that the Spares co may have been supplied with the wrong parts?. If the same mag fits a Velo( I suspect it is the same physically), could the taper boss be the incorrect one? Try to get the spares Co to take photo's of another fitting kit to see if it is the same as yours or Email BTH for some dimensions of the adapters, if they supply them..John

Thanks John, that is exactly what I am thinking....no reply over a few weeks from BTH though

 

[redbloke1956]

G'day Kevin.
From the wide and various selection of ignition parts in my spares cupboard (actually worn out but I don't like throwing things away).

The shaft taper is 11 mm minimum diameter (yes it really does seem to be in mm) and 13 mm max diameter NB at 11 mm from the minimum diameter end. Mag shafts seem to have a longer taper than my coil ignition setup, but they all seem to got from 11 to 13 over an 11 mm length. The 11 mm dia is 14.2 mm from the face of the mounting flange (not the spigot). the spigot is 2.7 mm thick, so the 11 mm dia is 11.5 mm from the spigot face.

The max bore on the ATD is 13 mm - I can't measure the min dia, or length of taper, but since its a snug fit on the shaft it should be the same dimensions.

When the ATDs fitted the distance between the mounting flange and the pinion face is 14.2 mm.

Hope that makes sense. Good luck.

H

ps it's not easy to measure a diameter on a taper with my measuring kit, so my measurements are only for starters.

Thanks Howard, sorry your kit is only for starters mate, they do get bigger as you get older though
Thanks though mate, that is what I was after, I will do some serious measuring with MY KIT tomorrow and let you know how it goes.
Kevin

 

[redbloke1956]

Dear Kevin,
Just a thought. When I looked back through your earlier posts you said:
"One interesting point though...I have noticed that the original ATD has had the taper resleeved at some point....there is no (or little) internal taper"
I wonder why this was done? Could it have been done to correct an assembly mistake?

Is it too daft a question to ask or is it possible that the train of gears was incorrectly shimmed out too far?

Thanks Eddy, I am a little confused myself here mate because in one of the pics I took of the timing case (pre disassembly), the mag pinion is in perfect mesh, I have since made sure all spindles are the correct height etc, and can't replicate the mesh?
regards from the confused
Kevin