PUMP IT UP
Jonathan Holmes makes his own aluminium tanks and suggests a leak-testing method I could have used to check my Norvin tank when I was struggling with it. He fits the cap and tapes over the breather hole, then lightly pumps in compressed air through the tap, shutting it smartly before all the air can escape, then immerses it in a dustbin of water, seeking giveaway bubbles. Thanks, John, but I’m not so sure that would have worked for me in
this case. My leak was only really apparent with a full tank; it was fine with half a gallon, so it was more a seep.
I have used the bubble test to repair a Scott radiator; it was great for locating original leaks. After soldering I blocked off all outlets and blew through the radiator breather pipe – no sign of bubbles. But on the first ride, it leaked again. The heat seemed to find leaks the air missed. Air seems to take longer to escape than hot or volatile fluids, so I’m a bit wary but thanks anyway! .
Nigel Landon had a problem with his 1970 Triumph Bonneville jumping out of gear – any gear, any time – making the bike almost unrideable. New selector springs didn’t help, but dismantling further he found wear on the selector camplate. Ordering a replacement, he was surprised to find it was significantly different, with no notches in between gears as on his old one. “Are these older, pre-unit gearbox parts?” he asks. “Are they interchangeable and if it’s a complete early gearbox, will that cause further problems?” My own ’68 TR6 has an earlier gearbox because it has internal speedo drive gears, used prior to 1966 when the drive moved to the rear wheel – but that aside I wasn’t sure about parts interchange, so I spoke to Arthur at Triumph specialists Rockerbox in Farnham, Surrey (01252 722973). Arthur said that four-speed unit and pre-unit gearboxes are interchangeable, but it’s best not to mix parts as there are slight variations over the years. Arthur also pointed out that 1970 was the year of the short-lived camplate leaf spring instead of the more familiar detent plunger; many owners have bored out the gearbox shell to fit a sprung plunger and problems arise if it hasn’t been done accurately.
Nigel’s problem turned out to be simple – his bike just predates the leaf spring, the camplate he ordered is for the leaf-type, so his notched original is correct for his bike although the two plates are interchangeable. The bike wouldn’t stay in gear because the detent plunger spring was about ½in too short; fitting a longer one sorted it. As he said “All that time and expense just for a $1.50 spring!” We’ve all been there, Nigel…
You’ve got to be careful when ordering Bonneville camplates