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September 2007

Throttle Cables

This was a strange one ? my brother came round and took the car for a drive, but after about 2 minutes rang me and told me that the throttles had jammed wide open and I needed to recover the car!!!

When I got to the car I fairly soon figured what the problem was and fixed it enough to get it back to the house where the pondering started... The tiger is fitted with a pair of twin Dellorto carburettors which have a dual throttle cable linkage fitted to them as well. This linkage requires the cables to exit straight back from the carbs i.e. into the rocker cover. To account for this the cables then bend over the rocker cover and down towards the pedal box. What had happened was one of the cable outers had moved slightly and the inner cable had been rubbing on the cable guide. The cable had worn a slot into the guide and then chosen this afternoon to get jammed in there locking the throttle open. So I needed a repair fast.

It was apparent that the cables themselves would need replacing and as they are bicycle brake cables (honestly check if you don't believe me) a quick trip to Halfords was in order (as the only bike shop open on a Sunday for miles). Whilst there I was also looking at the bikes themselves and noticed on the V brake system the use of a metal tube to bring the brake cables into the arms at the correct angle. This is basically a short length of tubing with a plastic insert that allows a cable to bend 135 degrees ? an idea was born. So I bought 2 of the tubes, a pair of inner and a pair of outer cable along with the proper finishers for the outer cable.

Once home a bit of careful bending reduced the tubing from 135 degrees to 90 degrees, the outer cables were cut long enough to go down the engine bay around the nose of the engine and return to the carbs where they were inserted into the tubing and then into the control linkage for the cabling.

The result is the a pair of cables that are directly routed around the engine with no sharp bends and should work perfectly in all conditions although at the time of writing it hasn't been tested on the road as yet there is no reason why it should have any difficulties (famous last words).

View of carbs Detail of cable runs