donaldremnant

i have a yamaha 1979 rs200 that refuses to run on its right hand cylinder. two sets of new points have been fitted with condensers. timing checked, new plugs, head & cylinder removed, good rings, good barrel, gaskets renewed, good spark, only single carb, no reeds, left cyl runs fine. i am at a lost to what can be the problem & the cure, HELP, HELP. DON REMNANT.