I have a Vespa Ciao that has a little trouble when any gas is given. It tends to rev quite a bit unless I slowly give it gas up to full throttle--very finicky. It runs well besides the reving. Could the clutch be slipping? Would new clutch springs help out? They seem to be a tad bit rusty and lacking a little spring action. The shoes have plenty of pad left to them...I roughed them up with a little emery paper, but still no luck. Any ideas? Thanks.