- Mon Dec 04, 2017 11:44 am
#72645
Well, it looks to me like there is an excessive amount of free play on the throttle cable. Can be due to one of two problems.
1) Lack of adjustment, there is an adjuster screw with a locknut on top of the carburettor which should be adjusted so there is only a small amount of slack with the throttle fully closed.
2) Throttle valve not returning to fully closed position. Several possible causes, the most likely of which is that the throttle cable is poorly routed or pinched between the tank and frame (this is very easy to do). It can also be the throttle valve itself sticking in the carb body.
If you listen carefully to the carburettor as you close the throttle (engine off), you should be able to hear the throttle valve hit the idle stop with a "clunk" when it reaches fully closed. If you can keep closing off the throttle from here, the cable needs adjusting. If you don't get that clunk and that free play you're getting on the cable apears, the cable is sticking.
If the cable is sticking, you'd probably get a very fast or intermittantly fast idle when the engine is run.
For a sticking cable, first thing I'd do, after optimistically wiggling either end, is whip the tank off and make sure it's free to move along the frame and where it runs in through the casquette with a minimum of sharp turns. It generally wants to be going vertically into the carb, there isn't a lot of room under thew tank to achieve this. Once you're happy with it, then put the tank back on taking care how it's routed under the tank and checking it's still free to move at each stage.
I usually have to have a couple of attempts to get the cable well routed and not sticking.
I suppose something else to mention is some cables come either overly long or sticky from the get-go (even ones from reputable suppliers). I usually land up making my own.
