tach drive

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sean

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hi
I am missing the tach drive on the outside of the timing cover reading a previous thread it seems there are different ratios between years my engine number is 20 M 3 / 127073 I am assuming this is the stock 1969 engine as the frame numbers match up but how do I figure out which tach drive I need ?
Thanks
Sean
 
sean said:
hi
I am missing the tach drive on the outside of the timing cover reading a previous thread it seems there are different ratios between years my engine number is 20 M 3 / 127073 I am assuming this is the stock 1969 engine as the frame numbers match up but how do I figure out which tach drive I need ?
Thanks
Sean
Click to expand...


With that engine number, and the tach drive coming out of the timing side cover, I think you have a 1968. 1969 models started with #131180, making yours one of the first 1000 produced. I have a #127129 and it is a 1968. The plastic Norton discs recessed in the tank and tailpiece are also 1968. Do you have a distributor behind the cylinders?
The Atlas tach drive looks the same and fits, but it would be the wrong ratio. NOS are available, but $$$$$.
Also if you have an original frame, it may need to be strengthened. Read this thread, check out the photos of the frames. They can be repaired.

1969-fastback-rebuild-t9542.html

Mick
 
The tach drive you are looking for would have the numbers '1508/06' on the lip of the mounting flange which is a 2:1 drive. These are pretty much just for the Commando, and were only put on a few thousand bikes, as the change to points on the end of the cam came during the 1970 model year.

There is and identical-looking tach drive, marked,'1508/00', '1508/04' or '1508/05', which was used on a bunch of different bikes in the '60s, including every Norton with a tach, a few BSAs, and most Matchless and AJSs .
This drive is 1:1, which means your tach would read double the actual RPM unless you changed to a 2:1 tach from the stock 4:1

There is also a drive, '1508/01' which is a 2:1 drive like you need, which was used in Royal Enfield twins such as the Constellation and Interceptor.

There's a reproduction made, which I believe runs around $260.
 
commando6868 said:
sean said:
hi
I am missing the tach drive on the outside of the timing cover reading a previous thread it seems there are different ratios between years my engine number is 20 M 3 / 127073 I am assuming this is the stock 1969 engine as the frame numbers match up but how do I figure out which tach drive I need ?
Thanks
Sean
Click to expand...


With that engine number, and the tach drive coming out of the timing side cover, I think you have a 1968. 1969 models started with #131180, making yours one of the first 1000 produced. I have a #127129 and it is a 1968. The plastic Norton discs recessed in the tank and tailpiece are also 1968. Do you have a distributor behind the cylinders?
The Atlas tach drive looks the same and fits, but it would be the wrong ratio. NOS are available, but $$$$$.
Also if you have an original frame, it may need to be strengthened. Read this thread, check out the photos of the frames. They can be repaired.

1969-fastback-rebuild-t9542.html

Mick
Click to expand...
hi
yes looks like it was a left over 68 registered in 69 .....I thought there was a recall on defective frames ...yes distributor behind the cylinder ......the indentations are in the tank for the Norton discs but there are none ....I dont know any details on the bike as I bought it in an estate sale its been sitting in a garage since 1979 ......great job you did on yours
 
BillT said:
The tach drive you are looking for would have the numbers '1508/06' on the lip of the mounting flange which is a 2:1 drive. These are pretty much just for the Commando, and were only put on a few thousand bikes, as the change to points on the end of the cam came during the 1970 model year.

There is and identical-looking tach drive, marked,'1508/00', '1508/04' or '1508/05', which was used on a bunch of different bikes in the '60s, including every Norton with a tach, a few BSAs, and most Matchless and AJSs .
This drive is 1:1, which means your tach would read double the actual RPM unless you changed to a 2:1 tach from the stock 4:1

There is also a drive, '1508/01' which is a 2:1 drive like you need, which was used in Royal Enfield twins such as the Constellation and Interceptor.

There's a reproduction made, which I believe runs around $260.
Click to expand...

thanks for the help at least I know what to look for now ....we have a big vintage swap meet coming up in a couple of months so I will keep my eyes out for these part numbers
 
Your frame probably has the VIN # stamped into the headstock as opposed to having it on plate attached to the headstock. If you add a section of tubing to strengthen the stock frame, you will have to go with an aftermarket head steady and probably change the coil mounts.
Not many stock 1968 Commandos around.
The photo I have on here is of my 1975 with Craven bags and other stuff added.

Good luck with it.

MF
 
JohnTy said:
Hi Sean
RGM http://www.rgmmotors.co.uk/home.htm have the drives listed (under levers/controls/pedal section?) they are £99 ($140 ish) not cheap, but if your stuck!

Hope this helps
JohnT
Click to expand...
thanks I have a brother in England so I could save on the shipping as he visits a few times I am in the teardown stage at the moment and just making a list of things I am going to need
Sean
 
sean said:
JohnTy said:
Hi Sean
RGM http://www.rgmmotors.co.uk/home.htm have the drives listed (under levers/controls/pedal section?) they are £99 ($140 ish) not cheap, but if your stuck!

Hope this helps
JohnT
Click to expand...
thanks I have a brother in England so I could save on the shipping as he visits a few times I am in the teardown stage at the moment and just making a list of things I am going to need
Sean
Click to expand...
Probably cheaper to have it posted or your brother in the uk will end up paying our vat tax @ 20%, am sure postage would be considerably less than this. It is a grand thing this European market :shock:
you can't beat paying through the nose for nothing!
JohnT
 
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