Speedo drives for the 750's

71Laverda750SF

71Laverda750SF

Hero member
Location
The Sunshine State
Reading, and re-reading, Ian's descriptions on each model change for the 750's I am a bit confused about the speedo drives for the Smiths instruments in general, and then the difference for the drive for the 220 Km/h and 240 Km/h speedo's. Are the drives at the wheel different, and if so, it would be a number of teeth issue so what would the numbers be for each. Also, I'm not really sure what drive I have now since my machine had ND's on it when I got it and it should have originally had Smiths. So is the Smiths drive for the 220 different than the ND drive?

Clay
 
Hi, Clay.
1.) Yes, drives for ND and Smiths are different.
2.) If you have an information with a 600 on the bottom of the Smiths clock face,
    you need a drive with 15/12 teeth.
3.) If it says 1000, you need the 22/11 drive.

hth,
Ernesto
 
Ernesto said:
Hi, Clay.
1.) Yes, drives for ND and Smiths are different.
2.) If you have an information with a 600 on the bottom of the Smiths clock face,
    you need a drive with 15/12 teeth.
3.) If it says 1000, you need the 22/11 drive.

hth,
Ernesto
Click to expand...

Interesting Ernesto! I have a speedo in miles, what sort of drive in your opinion?
 
MVma said:
Interesting Ernesto! I have a speedo in miles, what sort of drive in your opinion?
Click to expand...

Jean-Louis,

Don't think the drive will differ, usually only the dial faces of the instruments were swapped for KM/H or MPH.  At least that's how Smiths did it with their earlier chronometric instruments.

piet
 
Thanks Piet, but were there 2 different speedos in miles like the 190/240 kph? I ask because my speedo (newly restored) is totally wrong (and also the rev counter...).
 
120 miles so about 190 kph... Always seen 120 miles on any Smiths speedos but not 100% sure that there was only one model.
 
MVma said:
120 miles so about 190 kph... Always seen 120 miles on any Smiths speedos but not 100% sure that there was only one model.
Click to expand...

I can check tomorrow with a phone call. My speedometer repair folk have all the original Smiths documents.

In response to Clay(?)s Piet's post - just changing the face doesn't work 'cos the odometer is then wrong. But weirdly....I have one "Laverda" Smiths speedo with an odometer.....and one without !!

H.

 
Harry Lime said:
I can check tomorrow with a phone call. My speedometer repair folk have all the original Smiths documents.

In response to Clay(?)s Piet's post - just changing the face doesn't work 'cos the odometer is then wrong. But weirdly....I have one "Laverda" Smiths speedo with an odometer.....and one without !!

H.
Click to expand...

The odometer drive is taken off the speedo drive, also just a case of swapping a pair of cogs to suit. 

piet
 
MVma said:
Interesting Ernesto! I have a speedo in miles, what sort of drive in your opinion?
Click to expand...
Hi JLO -It sounds like you do not have the small SSM number at the bottom of the speedo. I bought a 750 which came with reconditioned smiths clocks. The speedo (miles) didn't have the small ssm number ending in either 600 or 1000 at the bottom. I think maybe someone had new faces made but wanted them to be usable for both types of smiths speedo hence leaving this detail off.
I wanted to buy gears for the front wheel but first needed to identify which speedo I had. My solution was to get a speedo from a 1970's Triumph (1.25-1 i.e. 15-12 ratio) and use a battery drill to drive it and observed what speed showed. I then put the drill onto the Laverda smiths speedo and noted that it showed the same speed.Thus I knew I had a speedo requiring the 15/12 gearset. I don't know if you could borrow a speedo from a 1970's Brit bike to do the same but if not some Harleys use a 2-1 ratio so you could use the same method to prove or disprove whether your speedo would use 22/11 gearset.
Laverda tachometers use a 3:1 ratio which is rare - lots of Brit bikes use 4:1 ratio so maybe someone has reconditioned one of these for Laverda?
 
Normski said:
Hi JLO -It sounds like you do not have the small SSM number at the bottom of the speedo. I bought a 750 which came with reconditioned smiths clocks. The speedo (miles) didn't have the small ssm number ending in either 600 or 1000 at the bottom. I think maybe someone had new faces made but wanted them to be usable for both types of smiths speedo hence leaving this detail off.
I wanted to buy gears for the front wheel but first needed to identify which speedo I had. My solution was to get a speedo from a 1970's Triumph (1.25-1 i.e. 15-12 ratio) and use a battery drill to drive it and observed what speed showed. I then put the drill onto the Laverda smiths speedo and noted that it showed the same speed.Thus I knew I had a speedo requiring the 15/12 gearset. I don't know if you could borrow a speedo from a 1970's Brit bike to do the same but if not some Harleys use a 2-1 ratio so you could use the same method to prove or disprove whether your speedo would use 22/11 gearset.
Laverda tachometers use a 3:1 ratio which is rare - lots of Brit bikes use 4:1 ratio so maybe someone has reconditioned one of these for Laverda?
Click to expand...

Hi Normski, many thanks for all that. Just checked the speedo, it has the SSM 1000 number. I checked also the old one, it had the same reference. I will see if I have the correct 22/11 drive.
Apart that, as long as I will be living around here in the islands, no way to find a Brit bike locally!!
Anyway, the speedo AND the tacho are wrong (speedo shows less, the tacho shows more)...
 

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Hi Ernesto, thanks for the offer, however I will stay with my speedo, just checking with Wolfgang what he has in stock for the drive that I have to replace anyway, maybe there are 2 different drives for the 120 mph Smiths speedo. Thanks once again!
 
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