Tag Archives: bronze head

Triumph head news

I got the invoice from SRM today to say that the work to re-commission the Triumph Tiger 100 bronze head has been finished. It’s all money of course but if they’ve done a decent job I’ll be so happy. It’s twenty five years since I took that head off to get fixed and there’s a lot of water under the bridge since then. I like a bit of continuity.
I spent most of my School lunchtimes at Owen Greenwood’s motorcycle shop in Loughborough in 1987/88. I had my first road bikes from him. First a Simpson 50cc and then an MZ ETZ 125. I have no idea how many times I fell off them but he did call me ‘crasher’ Moss at one point. When he had the Triumph bronze head valves seats built up for me and my Dad, after my first season of racing with the VMCC, I doubt he considered that it would take this long to get the rest of the work done. He’d have called me a ‘messer’ without a doubt, but I know he’d be pleased that I was eventually getting back to it. RIP Owen Greenwood.

I’ve got to get barrels bored but I’m sure I’ve got a reasonable pair of pistons somewhere. It won’t be phenomenal but it should be somewhere in the mix in the 500 class. I don’t think the short stroke Manx Nortons need worry though…

The other main thing the Triumph needs is some attention on the breathing, I’ve looked into non return valves in the past but never got it completely sorted. It always did cover the rear tyre with a fine mist of castrol R. Nothing to the rear of the engine will ever rust on this bike. I’m sure a concerted effort will bring success, although I have seen that from 2016 all road competition bikes (two strokes too?) will have to have a complete catch tank under the engine. I think a scraper on the sidewall of the rear tyre into a dangling bucket might work better. It’s no fun hitting oil though, so I’ll do everything I can to get it under control.

The head question

I’ve been trying to work out what to do regarding the Triumph cylinder head. I’ve not built this engine up as a 500 for years and it’s not really a ‘bolt together’ job as it is.
I started racing it in 1988 and at that point it had the bronze head. It was the first geared bike I’d ever ridden and the first time I rode it was at a Cadwell park practice day. I remember seeing these RC30s screaming by me at every corner of the track. It was dangerous of course as novices (and especially ones that can only just ride a bike) are completely unpredictable. I survived though.
After my first season, we stripped it and realised that the valve seats were quite sunken by many years of use (no seats.. straight on the bronze)IMAG0522 so we asked Owen Greenwood in Loughborough to have the bronze head seats built up ready for re-working and in the meantime I ported an iron head for that season. I obviously enjoyed using the air grinder as I definitely took enough metal out(!). In one place the seat is thin enough that I worried about overheating. No multi angles, no finesse! IMAG0516 We ran that head for another season or two and then it didn’t get run again until I rebuilt it to take to the Beezumph in 2001. I should have left it alone but I was obviously seized by the desire to improve it. This seemed to involve skimming 0.080″ of the head and the barrel spigot in order to increase the compression ratio.Doing this causes all kinds of issues as you have to deal with the sealing of the pushrod tubes and the lengths of the pushrods. IMAG0517It was misplaced endeavour, but it probably was fun at the time. Unfortunately There wasn’t enough clearance and the substantial 1.5″ inlet valves (Norton Atlas if you’re interested) contacted the pistons. It didn’t result in carnage, but we knew that it wasn’t really running right so I only did a couple of sessions.
I didn’t start racing with the VMCC again until around 2008-ish, twenty years after I first raced with the club, and this time it was with the Scott, but the following year we rebuilt the Triumph with the big motor (680cc) so the 500 has lain unused and unresolved.
I think considering that if I had no other options I’d be justified in re-working the skimmed head, but I think I’d keep my life as easy as I can. It’s not like I have a lot of time, so I think I’ll stick to either re-doing the bronze head or an iron one. Time to get some prices for hemisphere recutting!

Roger on the Triumph  with 680cc motor in mid 1970's rounding Mansfield corner at Cadwell Park
Roger on the Triumph with 680cc motor in mid 1970’s rounding Mansfield corner at Cadwell Park

Richard at the September Cadwell meeting in 2008 (or 2009?) on the Triumph. 680cc motor fitted.
Richard at the September Cadwell meeting in 2008 (or 2009?) on the Triumph. 680cc motor fitted.