I just put a new throttle cable on my mower and when it is at full throttle the cable keeps creeping to back to about half. I tried to tighten the cable clamp as tight as I could get it and it still creeps back. I took the clamp off and straightened it out put it back on tight but it still creeps back. I don't think I could get it any tighter without crushing the coiled jacket, but it's tight enough to hold it in place. Any ideas?