Hi. I need help with my 84 Honda xr250r. Broke off an intake valve so I bought a used head. Timed it with the cam lobes facing down, the timing marks level with the head at tdc on the flywheel. My issue is that when I put the valve head/cover on there's no compression (very easy to push the kickstart) but if the valve head/cover is off then the compression is normal ( meaning it's hard to push the kickstart). What would cause this?