The throttle started sticking open a while ago, so I’ve a) put a Buttys throttle linkage on, b) replaced the cable, c) replaced carb springs and d) made sure everything is all nice and tight along the full length. But.... ITS STILL *****ING STICKING OPEN?!?! Any more than 1/2 throttle and the engine just screams. Peddle returns to top and a few taps of it seem to free something up and it settles back down. Any thoughts on what else could cause it to massively over rev?
Think you may have answered your own question in the post ....a few taps and it seems to free something up... something is sticking/ catching ...check and check again. With all the things that you have changed, only seems to leave the cable conduit .....rust or a kink somewhere perhaps?
Almost certainly . I’ve just spotted that I’d run the cable over a pipe at the back of the engine bay rather than under it so have rerouted that and am about to take it out for a run. Thinking that it was being pulled up and backwards so may have been catching on the edge of the hole rather than being pulled clean through it. Failing that, I’m gonna run new copper conduit from front to back alongside the current one.
Disconnect the cable from the carb. Does it still stick? Your answer will determine whether the problem is the linkage or the carb.
How old is the carburettor ? A well worn Solex can easily hang up the butterfly plate in wear grooves so it locks open. A new throttle cable wont stick internally, but people have had trouble with the flexible outer section above the gearbox not being pushed in properly in the gearbox support frame and causing fast running ( because it effectively shortens the throttle cable) and stickiness.. If the carburettor throttle spindle has any side to side slop then this is likely to cause the plate to jam. Stamping on the throttle makes it bang shut. If you have this problem, rebushing kits are available for 34PICT-3 , and for the creatively desperate you can always buy 8x6mm Oilite bushings for a few pounds, and drill out the carburettor body to acommodate them with a pillar drill. I had to do my progressive carburettor as the junk EMPI linkage I used at first pulls hard sideways on the spindle as you try to haul in the last possible 5 percent of throttle opening ..which still is not wide open throttle Adding more springs and fiddling around may just make it worse as the springs increase wear by pulling sideways when installed too 'creatively' such that they increase sideways force required to open the throttle. I have also had a problem where the choke stepped cam would jam but that did not clear up after stamping on the pedal.
