Nigusil Plating

Got the V50 top end stripped down as I had a couple of burnt out valves, turns out the rings are stuck as well (bikes been stored for a few years outside before I got it). Anyways looking at the bores how do I tell if the Mk3 Nigusil bore plating is in good condition? The bore isn’t smooth its got a few minor vertical lines in it but no deep ridges. Quite willing to have it replated but I don’t want to if I don’t need to.


On mine, I had occasion to lift a head at about 15k miles when I touched a valve (stuck down after a winter layup). Half way down the bore I found a patch of the plating – probably around the size of a half crown, was missing. The plating is quite thin of course – but it was quite bleeding obvious. I replaced with a brand new matched piston and barrel. I pulled the heads again at 48k miles to replace all four valves as they have a reputation for stretching and dropping the heads. All was fine. I pulled the heads and barrels at 55k miles to replace the piston rings – I was getting excessive oil blowing into the air filter. I inspected the plating quite carefully on both bores at this time. You could still see the cross hatching from the original hone (I guess). Pretty damned impressive I thought. So I’d expect you to find one of those two scenarios.