Adding a tacho to a 1949 A7 long stroke with SRM oil pump

[pdg]

Hi,
I'm planning to change the oil pump on my 1949 A7 long stroke to an SRM item (http://shop.srmclassicbikes.com/a7-a10-oil-pump-srm-billet-high-delivery-improved). The new oil pump comes with a tach drive capability. If I drill a hole through the inner timing cover, does anyone know if there's a cable adaptor that would fit onto the inner timing cover? It's the angle I'm most concerned about, because the axis of the tach drive on the oil pump isn't at 90 deg to the face of the timing cover.

Many thanks, Peter.

[WozzA]

  I dont think it's just a case of drilling a hole in the inner timing cover...
you'll need one like this.. 

[muskrat]

G'day Peter.
The long and short stroke's inner timing covers are different. So it would be a cut and shut job. Cutting out that section off a late A7/10 inner and welding it into the long stroke cover.
Cheers

[pdg]

Many thanks for your replies. I'm thinking of making a wedge with 2 holes that I can then bolt through with the drive attachment to give the same effect. I'll also need to make a paper gasket to go between the timing cover and the wedge, but hopefully that should work?

I then guess it will be a 1:1 drive and I'll have to look for either an anti-clockwise or clockwise tacho when I see which way it rotates - RC1307/01 or RC1309/00?

Regards, Peter.

[muskrat]

Why not find an electronic tach that takes a pulse from a spark plug lead.
http://www.amazon.co.uk/Spark-Engine-Digital-Tachometer-Motorcycle/dp/B009Z7RE1W
Cheers

[pdg]

Many thanks for your suggestion. I've looked at various options including http://puca.co/index.html and I'm still trying to work out which way to go - electronic or mechanical.

The electronic option requires a 12V supply which can be done with DC-DC converter, but clearly involves some wiring and hiding the converter. The bigger issue is that in using the pick-up from the HT lead to drive the electronic tacho suppressed spark plug caps must be used. I understand that suppressed caps are not recommended for use with a magneto.

The mechanical option is not without its difficulties, but I've got a spare inner timing cover and access to machining facilities to make the wedge shaped spacer that would be needed.

Jury's still out. Any advice about the use of suppressed caps with a magneto would be useful.

[muskrat]

The one I gave link to is self powered and cheap. Not mentioned is thje need for suppressed caps.
Cheers

[chaterlea25]

Hi Peter,
The oil pump runs at 1/3rd engine speed,
The rev counter needed is the RGS or late SR , RC 1303/03     
It also runs reversev cable direction to "normal"
These are very sought after so very expensive?

Would it be worth considering a drive from the magneto pinion as on Road Rocket or single cylinder models?
Expensive again though

Have you looked at these electronic rev counters housed in a very original looking casing?
http://www.beckelektronika.nl/
They also supply a 6-12v converter if needed

HTH
John

[pdg]

Hi John,

Many thanks for your really helpful message.

I've looked into the Dutch option, but it needs an HT ignition system, & at this stage I didn't really want to swap over from a standard magneto.

http://puca.co/index.html also do a good alternative, using a sensor on the plug lead, but it requires suppressed caps and I've been given conflicting opinions about whether or not it's ok to use supressed caps with a magneto - your thoughts on this would be welcome.

Hence looking at making use of the SRM oil pump upgrade.

Regards, Peter.

[chaterlea25]

HI Peter,
I replied to your PM, same as your post here but I dont have the reply saved?
Could you post the reply here?
John

[pdg]

Hi Peter,
I thought the dutch one used a pickup on the HT cable like a strobe light one or similar ??Its been a long time since I looked at their stuff???
If your old oil pump is ok then a later cable drive piece could be fitted to it???
That said I have only good things to say about the SRM pump, and fit them to all my rebuilds
I sold all the old pumps at autojumbles so dont have a drive for you to try 
One of the forum members runs a UK business and has modified the standard inner cases to take the cable drive
Have you found this topic? http://www.a7a10.net/forum/index.php?topic=4557.0

[pdg]

Hi John,

Many thanks for your reply (which I've posted above). I've been told about Bob Wardley, so will get in touch with him.

My immediate problem is understanding how to set the timing - I've listed a new posting on this.

Regards, Peter.