Q. I've just got a very keenly priced ZXR750 dating from the early ’90s but the handling seems very choppy no matter what I do to the rear suspension.
I didn't get much paperwork with it, but it seems pretty clean, if cruddy in places under the bodywork.
Andy Waterfall, email
A. No service history and a cruddy frame could mean that the suspension needs an overhaul, specifically the rear suspension linkage.
If you're lucky there will be grease nipples fitted to the linkage, most bikes from that era don't have them. The linkage bolts all run in bearings within the linkage arm and they are hung out to get every bit of road crud going.
It's essential they are serviced regularly and regreased, or they'll wear rapidly and eventually seize up.
You need to support the rear end of the bike with a strap around the swingarm and frame, and remove each nut and bolt carefully, noting which hole they need to be returned too.
If you're lucky the bearings won't be worn and you can clean the linkage up and regrease them. Check by trying to rock the bearing collar back and forth – if it rocks at all the bearings need replacing.
When you clean up the linkage, don't use any petrol-based cleaners as that could damage the bearings' protective rubber collars.