This what works for mine: from Amazon

https://a.co/d/iK5TI93

 

These show to be 1.905 mm thick- if Triumphs are 3 mm that is significant especially if the 2mm gave @Tyrannosaur trouble. Next stop at the dealer I think I will grab a few just to have on hand.

 

It's not essential to replace a drain plug washer every time you change the oil, in my view. If you have a spare one, fine. Otherwise, just make sure everything is clean. You can always put a smear of gasket compound on the surfaces or, if it's a copper one anneal it by heating to red hot in a flame.

 

......or, if it's a copper one anneal it by heating to red hot in a flame and quenching it in cold water.

There, finished that off for you.

 

Sometimes the dealer includes the washer and charges you for it.

It is a common 14mm ID aluminum drain plug washer available at almost every auto parts store.

 

I actually had a problem with the standard crush washers from the auto parts store on my 2016 R. The threads on the drain bolt didn't go all the way to the flange, so when I tightened the bolt, it was running out of threads before it got really solid contact with the crush washer. The torque on that oil drain bolt is only 25Nm, and I think I was reaching that value with the threads just ending, not with the flange of the bolt really contacting the washer very well. It looked OK, but it very slowly dripped oil. Like one drop every day or two. Who knows whether I lost any while riding, but the oil was never low, just an annoying oil spot on the garage floor.

The genuine Triumph washer is 3mm thick, vs. 2mm for the generic ones that I had, and that solved the problem. I've always wondered whether that was deliberate engineering on Triumph's part, to force me to buy their genuine Triumph crush washer, or just a manufacturing tolerance issue on the bolt on my bike.

 

The Triumph washer is 14.4mm ID and 3mm thick and so are the quality washers, like Doorman, at the auto parts stores.

The cheapest washers seem to be exactly 14mm ID and thinner. That's the difference.