I bought my 7 year old son a DS90 last year. He has been wearing it out with no problems for the past year. In the last few weeks it seems as the clutch is slipping, slow to get going until warmed up, slows down up hill. I went by the local dealer to see about getting it serviced but his young mechanic knew less than i did about it. Is there any type of adjustment for the clutch or do you replace it when this starts? Thanks for any help.