Saturday 27 February 2016

Why TR1s always blow their headgaskets (and what to do against it)

I currently own two TR1s. One is the Turbo Bike and the other is my slightly more conventional everyday ride.

Now truth be told, a stock TR1 is a pretty rubbish bike. Firstly it is relatively slow for a 1000cc v-twin and secondly it is pretty unreliable by Japanese bike standards.

The first thing you have to be aware of with a stock TR1 is that they have a really weird headgasket, made from a pressed asbestos ring, which sits neatly in a groove. It wasn't exactly the world's worst idea, but on Mk.1 TR1s (the ones marked with 5A8) there was no separator between the groove for the headgasket and the rubber seal of the camchain tunnel.

It's a pretty rubbish design

Luckily later XV1000s and XV1100s sport a conventional style fibre or multi-layer metal headgasket. The 1100s even sport the same bore, but it's not that easy. If you want to go for the full monty, you have to go for an 1100 crank and pistons as well. 

But you don't necessarily have to go for a later cylinder, there's two alternatives for you to modify the stock cylinder, yet both involve a bit of machine-work. Number one is to have the gap between the headgasket groove and the camchain-seal welded up and then machine it back the correct height. This is the bolts 'n' braces way to do it and exactly what Yamaha offered to upset customers in 1981 and 1982 and made stock for the Mk.2 TR1s (marked 19T). A more simple way is to cut a very thin slot with a 1mm-disc on your angle grinder into the space between the headgasket groove and the seal and then stick in a bit of stainless steel sheetmetal.

Bit hard to see, but this one doesn't have a groove

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