Ducati Owners Club of Victoria

Twist Grips and Throttle Cables

After persevering with the three cable throttle system on my 750 GT for years, I finally changed over to a twin cable set up. The only reason I put off this modification for so long, is that the switchgear is incorporated with the twist grip and the clutch lever. This meant that not only did I need to purchase a twin cable grip and cables, but also a plain clutch lever and a new left hand switch block assembly.

Two things finally prompted me to act. The first was a broken main cable which happens every now and then, due to the main cable taking the load of both carby springs, and secondly Steve Ekes book on Ducati tuning states that "if the bikes true potential is to be achieved, then the standard three cable set up should be discarded". Apparently the three cable set up will not open the carby slides fully in some cases and the added cable and junction box makes for increased friction and more trouble trying to balance the carbys'.

I wasn't expecting any startling results, just lower maintenance and easier adjustment, but the new set up seems to have given the bike an extra 10 HP. Most of this is just the easier throttle action, but the bike seems to run much smoother at all speeds.

Another problem associated with carby adjustment, is the wide variety of throttle cables available for Ducatis'. Once again I came across a cable that didn't have enough bare wire exposed which meant that even with the carby adjuster screwed fully down, there was no slack in the cable. It is imperative that at least 2 to 3 mm of slack exists on both throttle cables or you will never be able to tune the carbys' properly.

I have seen people trying to adjust their carbys' with vacuum gauges and they can't seem to get the two needles to read the same at idle. This is due to the cable stopping the slide from dropping onto the idle adjustment screw, so that no amount of turning this screw, will change the throttle speed. If you come across a cable like this, then you will have to shorten the outer cover.

Carefully remove the chromed cap from the cable and using a triangular file, remove one or two turns of the outer cable being careful not to mark the inner cable during this process. Replace the cap and make sure it seats down hard on the outer cable, some trimming of the plastic covering may be required.

The length of the outer cable seems to vary also and as it is important that the cables are not strained even at full steering lock, you may find a new cable too short to fit where your old one went. Route cables along the easiest path with the minimum number of bends, and don't tie them together or to the frame as this will restrict their movement.

After fitting new cables you will find that you may have to re-adjust the carbys' several times as the new cables bed in. As the two cables are different lengths, they tend to stretch unevenly throwing the carbys' out of balance. If you are changing from 32 to 40 mm carbys' you will need two new cables and you may also have to change the throttle grip as some cannot be adjusted to pull the extra 11 mm of cable, and will not allow the slides to open fully.

Sample cable lengths are shown below (note...free length of inner measured between nipple & end cap. Values approximate only.)

3 cable set up GT, GTS, 30 & 32 mm carbys'.

Main Cable...Inner 77 mm, outer 610 mm.

Short Cable...Inner 94 mm, outer 182 mm.

Long Cable...Inner 94 mm, outer 580 mm.

2 cable set up 30 & 32 mm carbys'.

Short Cable...Inner 106 mm, outer 600 mm.

Long Cable...Inner 106 mm, outer 990 mm.

2 cable set up 40 mm carbys'.

Short Cable...Inner 117 mm, outer 600 mm.

Long Cable...Inner 117 mm, outer 990 mm.

With regular lubrication the twin cables will last for many years It is cheap insurance to always carry spare replacement cables for both throttle and clutch. These can be coiled up and tied to the frame under the seat until needed.

Original article by Peter Shearman, February 1988