I had same problem but the sounds of things, rough taking off at lights and no power on accleration, this was when i first got my ke70, i noticed that the throttle pump on the carby was missing its clip, this sorted the problem, i put a new clip on and i was running better, altough not too great, i advanced timing a bit, fiddled round with mixture. another problem it could be is possibly a manifold gasket leak, pretty common on these as exhaust mani is steel and inlet it alloy and heat up and different temps and expand, hope this helps