Chain link trauma
John Birchill had a nasty surprise when he checked out this Speed Triple’s chain
‘Repeated hits had caused the softer hollow pins to become brittle’
When a six-year-old Triumph Speed Triple came in for an MoT it looked pretty clean. But as soon as Stourbridge Motorcycle Centre boss John Birchill took a closer look, he realised there was no way he could pass the bike. John explains: “There are three designs of link to join two ends of a drive chain; small capacity bikes have a split link with a clip, then there are two types of riveted links for higher-performance bikes, with either solid, or hollow pins, also known as ‘hard’ and ‘soft’ respectively.”
Most chains use the hard link design where the ends of the pins are peened over to resemble a mushroom top and hold the sideplate in place. Ideally you would use a chain riveting tool, although you can get away with gentle and accurate strikes from a hammer with a heavier hammer pressed against the back of the link.
But the DID chain on the Triumph uses the hollow link system which needs a different procedure. In this case a chain breaking and riveting tool that’s like a centre punch. It locates on the hollow centre and is wound down so it splays each pin head out about 0.5mm all round.
“Once the tool is centred you only need to turn it a little. Even with all our experience we use a Vernier gauge to check it, because it’s easy to go too far and then you get problems such as stiff links. “But this rider had set about the link with a hammer, and applied the same force as for a solid pin. But because the hollow pins are softer, the repeated strikes had caused them to become brittle and start to peel. “When you think about the speed a chain runs at and all that horsepower going through it, the consequences of the link failing are scary. The broken chain could easily thrash around and hole the crankcases – or your leg.”