Motorcycle Repair: 1st gear slipping?, yamaha xs650, wet clutch

Question
Michael,

My son has a 1980 yamaha xs650 and after a very short warm up period, starting off in 1st gear it will slip and engine will rev up and then catch back... go a little bit and then slip again with engine rev... doesn't do it in any other gear, just 1st...

Any suggestions as to the problem and how to fix it?

Thanks ,,, Dad of Nick

Steve

Answer
Steve, dad of Nick,

The first thing I would reccomend is to make sure the gearbox is filled to the correct level w/ the proper oil (typically straight 30 wieght).  This is a "wet clutch" and requires the proper amount of oil to operate correctly.  Also make sure the clutch cable is adjusted correctly, left w/ a little bit of free play.  It's tough to say w/o experiencing it 1st hand however, if the clutch checks out you may be dealing with broken transmission component, most likely a shifting cam or it's spring.  Most bikes have these inside the gear box but some have them outside, between the case and the clutch cover.  Remove the clutch cover to investigate what is accessible.  If your experiencing a definite sudden loss of gear engaugement accompanied by a clunk and not a "slipping" or more smooth loss of power you may indeed have to split the case to solve the problem. Any clutch problem can be remedied easily by replacing the worn components.

Hope this helps,
Mike