Tuesday 17 October 2023

Finding Your Way Around OEM's Giving Up on Parts Support: Triumph 955i Fuel Injection Seals

With Triumph giving up on my Tiger before I'm prepared to, I'm going to document the research and give details on what works when you're trying to keep a Triumph 955i's fuel system working by replacing old o-rings.

This has involved a crash course in o-rings and engine operating temperatures. As I work out a fix here I'll post details on o-ring sizing, what type works and include data on measuring the intake manifold at temperature.

It's been all Concours for the past few weeks while the Tiger is laid up. I'm hoping to get the fuel system sorted before the snows fly and I have to wait for next year.

Here are the measurements for the upper and lower fuel injector seals. The classy move by Triumph would be to open source publish the technical details for all the parts they no longer support so that the rest of us can get on with keeping the history of the marquee alive. With that in mind, here are the deets for the upper and lower fuel injector o-rings:

The thick ones go on top where the fuel injector meets the rail. My best guess is 3mm thick by 1.5cm outer circumference.

The skinny ones go on the bottom where the fuel injector slides into the intake manifold.

My best guess there is 2mm wide by 1.4mm outer circumference. 

Unfortunately, buying off the shelf boxes of o-rings isn't likely to get you anything that fits. The two below from Amazon didn't. This thing looks handy: https://www.allorings.com/O-Ring-AS568-Standard-Size-Chart.

The Tiger is a metric bike, so I'll work in mm (if Triumph went imperial on o-ring, what the actual f***). The thicker o-ring is 1.5cm or 15mm outside diameter (OD) and (I think) about 3.5mm cross section (CS). Looking at that chart, the #203 is a 14.58mm outer diameter with a 3.53mm cross section. That makes it mighty close. What would be nicer would be if Triumph just came out and gave us the precise sizes for these parts it has discontinued. Triumph?

The thinner one is also a 1.5 (ish) mm outer diameter (15mm-ish), but the cross section is thinner - perhaps two and a bit mm, and they have a 2.62mm cross section standard o-ring size. You'd have to hope Triumph didn't make bespoke o-rings for their fuel injectors, right? For the skinny o-ring I think I'd take a swing at the 2.62mm cross section / 14.43mm (1.443cm) size.

The All O-Rings site also has a good description of the materials you want to get your o-rings in. Nitrile and Viton are what I went with in the pointless Amazon order, but those are the materials you want in a fuel heavy application like this.

That's the configurator (right) - pretty straightforward, but it sounds like they manufacture each order, which probably won't make this a viable solution for someone just trying to keep their old Triumph on the road.

If only there was some kind of network of retailers who supported Triumph motorcycles who could order this parts to help their customers keep their older Triumphs rolling... some kind of 'dealer' network who understand how parts work and how to order this sort of thing in large enough quantities to make a profit while offering customers what they need.


How hot motorcycle engines runs: https://blog.amsoil.com/extreme-heat-is-hard-on-your-motorcycle/

Buna (Nitrile or NBR) o-rings: https://sealingdevices.com/o-rings/buna-n-o-rings/

Viton vs. Nitrile o-rings: https://www.nes-ips.com/viton-vs-nitrile-o-rings/

All O-Rings https://www.allorings.com/

They have sizing tools! https://www.allorings.com/o-ring-kits-and-accessories/o-ring-sizing-tools

I'd prefer to use All O-Rings for the parts, but they might be a B2B type of thing, and I'm not a B.

Amazon's kits:

Turns out Amazon's shot-in-the-dark kits didn't work either. There's more to this o-ring sizing caper to come. I wish I could just 3d print the nitrile o-rings I was looking for (doesn't look like it's additive manufacturing friendly).