Got a KH125. Occasionally in 4th, but mainly in 5th, when I get to 6000 revs it takes a while to get to 7000 revs. Sometimes it will hold the revs and increase bit by bit and sometimes it will increase, then cut out for a moment then increase then cut out for a moment and it can do this over the course of about 30 seconds. Also gets to 7000 revs then drops back down to 6 and the cycle starts again. Any ideas?