Gearbox pre-unit - Triumph Forum: Triumph Rat Motorcycle Forums
Classic, Vintage & Veteran For Coventry and Meriden Models. Anything pre-Hinckley goes.

 
LinkBack Thread Tools Display Modes
post #1 of 5 (permalink) Old 04-24-2010, 02:42 PM Thread Starter
New Member
Minitwins
Main Motorcycle: Triumph Pre-Unit
 
KB6552's Avatar
 
Join Date: Mar 2010
Location: B.C. Canada
Posts: 17
Gearbox pre-unit

I have noticed that some pre-unit gearboxes have a cable underneath the front running forward
The box I have does not have this

Is this a Speedo cable...?

What years did this cable begin to appear or maybe what year did they remove it?
KB
KB6552 is offline  
Sponsored Links
Advertisement
 
post #2 of 5 (permalink) Old 04-25-2010, 01:48 PM
Senior Member
SuperSport
Main Motorcycle: 1959 Triumph Bonneville
 
pre unit Thruxton's Avatar
 
Join Date: May 2006
Location: Rotorua, New Zealand
Posts: 1,306
Other Motorcycle: 2nd 1959 Triumph Bonne
Extra Motorcycle: 1982 R100RS BMW
Send a message via Skype™ to pre unit Thruxton
Post some photos please.
pre unit Thruxton is online now  
post #3 of 5 (permalink) Old 04-25-2010, 08:03 PM
Senior Member
Supersport 600
Main Motorcycle: the ones that run
 
Join Date: Jan 2010
Location: Land of Enchantment
Posts: 177
Other Motorcycle: The ones that don't run
Extra Motorcycle: Lots
All pre-unit gearboxes on bikes equipped with nacelles ("49 and later) had a cable coming out of the speedo drive on the right side. Earlier boxes do not have this cable. When the rigid box changed to the swing arm type the cable remained. It was finally changed to the rear wheel with the advent of unit engines. the speedo drive is a seperate unit on pre-nacelle models.
Robbie
Rubone is offline  
post #4 of 5 (permalink) Old 04-25-2010, 09:21 PM Thread Starter
New Member
Minitwins
Main Motorcycle: Triumph Pre-Unit
 
KB6552's Avatar
 
Join Date: Mar 2010
Location: B.C. Canada
Posts: 17
Thanks for the info.....

Here is a pic of one with cable...and the Box I have without


KB6552 is offline  
post #5 of 5 (permalink) Old 04-26-2010, 10:11 PM
Senior Member
SuperSport
Main Motorcycle: 1966 Thunderbird
 
Join Date: Feb 2010
Location: Atlanta, GA, USA
Posts: 1,149
Other Motorcycle: 1996 Trophy
Quote:
Originally Posted by Rubone View Post
It was finally changed to the rear wheel with the advent of unit engines.
Even unit 650 engines ran this up until about 1965.

The problem was that when you changed rear drive sprocket teeth, your speedo pickup error. Moving the drive to the rear wheel gave accurate readings regardless of gearing.


The GABMA newsletter. What's on the back of your toilet?

http://www.gabma.us/
GABMA is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Triumph Forum: Triumph Rat Motorcycle Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter your valid email address, that can receive an automated confirmation message. Otherwise, you won't be able to gain full access.

Email Address:
OR

Log-in









Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Similar Threads
Thread Thread Starter Forum Replies Last Post
Gearbox oils for unit construction Triumph engines? johnquinnell Classic, Vintage & Veteran 6 01-15-2010 09:09 PM
5TA Unit Gearbox Advice Twit Classic, Vintage & Veteran 6 11-05-2009 05:23 AM
English 101 DVD - unit & pre unit Triumph & unit BSA Motorcycle Maintenance DVD lowbrowcustoms Maintenance & Workshop Talk 2 08-23-2009 02:48 AM
Pre Unit 650 Gearbox Bad Oil Leak 1942u Classic, Vintage & Veteran 4 07-10-2009 09:54 PM

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome