RICK’S FIXES
Rick’s refusing to shrink from his ongoing quest to seal his Triumph oil pressure relief valve...
A rod for Rick’s own back
IN THE FEBRUARY FIXES, I wrote about sealing Triumph oil pressure relief valves, having found a source of thin-wall silicone rubber to replace the original (split and perished) internal tubing. After all, silicone gasket is both oil and heat resistant – just what you need in a valve working with engine-temperature lubricant.
Or is it? Rowland Kanner emailed me from the States to say: ‘Rick, being employed in the medical device industry, where proper material choices are critical, your recommendation to use a common silicone elastomer for a seal against hot motor oil hit me wrong’.
Admittedly, the valve I’d refurbished still seems to
Rick Parkington has been riding and fixing classic bikes for decades. He lives and fettles in a fully tooled up shed in his back garden. leak, so I read on, hoping to find something more suitable (better would do). Rowland directed me to a website: customadvanced.com/ chemical-resistance-chart. Type in a chemical – ‘lubricating oils (petroleum)’ – and the material – ‘rubber’ – and a suitability list appears. In this particular instance, silicone came out as ‘not recommended’, with the suggested options (predictably) being Viton and Nitrile rubber. I had looked for these originally, but couldn’t find anything in the crucial 4mm bore/6mm OD size; so back to square one.
Looking at my leaky valve, the tube was tight in the body but not on the spring retaining ‘nut’; it needed a tiny pipe clip, but even then you couldn’t fit it because the spring’s in the way.
The best I could come up with was a band of heatshrink – heating it through the spring made it shrink to grip the pipe. It seems to be working so far, although I’m sure Raymond is right – only time will tell if I get away with it or not...
‘IN THIS PARTICULAR INSTANCE, SILICONE CAME OUT AS ‘NOT RECOMMENDED’’