Throttle cables for twin carbs on a G12 CSR

Information relating to the Matchless G12 or AJS Model 31 650cc twin
Member
Posts: 95
Joined: Thu Jul 09, 2009 8:10 pm
Location: South Gloucestershire UK

Throttle cables for twin carbs on a G12 CSR

Postby CAB » Tue Jun 26, 2018 9:31 pm

Hello
I'm putting a 1961 G12 CSR back together and it is fitted with twin "Speed Kit" carbs and manifolds but I don't have any cables. I'm going to make some but before I do it would be handy to know the approximate lengths of the cables between the slides and 2:1 junction boxes and the twist grip/air lever and if any in-line adjusters are fitted. Does anyone have a set that they can measure or photograph?
Thanks in advance
CAB

Member
User avatar
Posts: 820
Joined: Fri Dec 09, 2011 5:33 pm
Location: Gauteng SOUTH AFRICA

Re: Throttle cables for twin carbs on a G12 CSR

Postby robcurrie » Wed Jun 27, 2018 2:57 am

I have a 62 CSR with Speed Kit that I can measure and photograph for you. I removed the chokes from the carbs, but left the cables in place.

Rob C

Member
User avatar
Posts: 820
Joined: Fri Dec 09, 2011 5:33 pm
Location: Gauteng SOUTH AFRICA

Re: Throttle cables for twin carbs on a G12 CSR

Postby robcurrie » Wed Jun 27, 2018 6:31 am

Here are photos of the cables, the length from the twistgrip to the adjuster is 150mm, from here to the splitter (seen above the rocker cover) is 400mm, from splitter to carbs is 275mm. The first length from the twistgrip has been shortened twice when doing roadside repairs due to the cable breaking at the nipple (make sure the drum in the twistgrip has a nice smooth transition to the exit point). The choke cable length to the splitter is 620mm and then they should be a similar length as the throttle cable to the carbs (mine are missing). As can be seen in the photos, the choke cable adjusters are soldered closed to prevent air leaks. The throttle cable is not routed along the handlebars so that it has a nice free loop to prevent unintended opening of throttle when turning; this loop should not be too big as to be a danger of snagging.

Rob C
You do not have the required permissions to view the files attached to this post.

Member
User avatar
Posts: 820
Joined: Fri Dec 09, 2011 5:33 pm
Location: Gauteng SOUTH AFRICA

Re: Throttle cables for twin carbs on a G12 CSR

Postby robcurrie » Wed Jun 27, 2018 6:36 am

Photo showing splitter and choke cable adjuster that is soldered closed. Ignore ignition coil behind the splitter - yours will not have this ... yet ;-)

Rob C
You do not have the required permissions to view the files attached to this post.

Member
Posts: 95
Joined: Thu Jul 09, 2009 8:10 pm
Location: South Gloucestershire UK

Re: Throttle cables for twin carbs on a G12 CSR

Postby CAB » Tue Jul 03, 2018 8:41 pm

Hello Rob

Many thanks for the photos and measurements. What was the reason for removing the air-slides? My bike came with electronic ignition (Boyer 6v I think it was) housed in a replacement body for the mag but I replaced it with a newly rebuilt mag after dad left the ignition switched on which fried the coil.... I recently stripped it to cure a load of oil leaks and blowing head gaskets; the sump plug had been welded up and re-tapped but the heat locally distorted the cases creating a gap. I've also had an O'ring groove machined around the filter tunnel and decided to fit the speed-kit kit manifolds and carbs instead of the single carb. I've had the heads rebuilt and ported by The Cylinder Head Shop and it's also got new speed-kit cams and followers and re-ground rockers. I've also got a set of Thunder Engineering rods to go in it when the new crank turns up.... I've decided to put it back together with the standard crank and rods (bottom end has about 3000 miles on it) rather than wait any longer - I expect it will turn up next week now that I'm ready to drop it in the frame.

Thanks again

CAB

Member
User avatar
Posts: 820
Joined: Fri Dec 09, 2011 5:33 pm
Location: Gauteng SOUTH AFRICA

Re: Throttle cables for twin carbs on a G12 CSR

Postby robcurrie » Wed Jul 04, 2018 4:16 am

Sounds like it's going to be a beast! Mine has the 10.5:1 pistons and composite gaskets don't last long; I made some copper gaskets after measuring up the head and barrel interface to make sure oil channel and pushrod tunnels lined up. In the composite gaskets, the pushrod holes were in the wrong position and would have rubbed on the pushrods.

Regarding the air slides (I call them chokes), they are not needed in my area as the tickler provides enough richness for cold starting and I can't have a problem with them coming on unintentionally.

Rob C

Return to G12 / AJS Model 31

Who is online

Users browsing this forum: No registered users and 6 guests