I'm lucky enough to be the custodian of several old motorcycles and this 1927 Triumph is a firm favourite. Bought some eleven years ago at auction, it started up willingly in the car park after I had paid up for it, and has been a reliable friend since.
The '27 Triumph really is one of the easiest flat tank bikes to live with, performance is fair and parts are available. It has that wonderful twenties long and spindly look but is combined with the advances of the latter part of the decade - wired on tyres and decent brakes. My example has been slightly blighted with a tendency to nip up when pushed along, I've always felt that more should be available from it and that it should have the ability to get thrashed a bit harder and take it.
So, some much needed care and attention for the Model N. The plan of action was to take the top end off and check for any possible air leaks, check the ring gap, lap the valves and give it a hone and hope that this multi-pronged approach would sort it out.
The first problem that sprung to light on disassembly was that the seals on the valve cap 'fir cones' were poor and possibly air was getting in. This would have to be sorted on re-assembly. Off came the exhaust and carb and next the barrel itself. Clearance was a lot tighter and the job was considerably fiddlier than I had expected for a bike that would have had to come apart regularly back in the day to de-coke and grind in the valves.
The ring gaps were already very generous, so no problems there. The valves were not seating nicely so out came the grinding paste and lapping tool. The bore was ever so slightly glazed so I got busy with the honing tool (just an attachment for my power drill). Whilst everything was apart the barrel and exhaust got the wire brush treatment followed by a couple of coats of high temp satin black paint.
Everything went back together the same way it came apart, the barrel was equally fiddly to get on as it was to get off. Just half an inch of extra clearance and it would be a cinch... Test ride time and it started and ran fine. Out on the road we took it steady to start with and progressively opened up more and more and all remained good with no sign of tightening up. Can't really say what was the single cause of the problem, perhaps it was multitudinous. So, ready for next season to ride with confidence in unleashing all those Triumph horses.