The Honda GB500 TT (“Tourist Trophy”) was inspired by the Isle of Man TT racers of the 1960s, bikes like the Manx Norton and BSA Gold Star. Then, as now, TT riders braved the 37-mile Snaefell Mountain Course, blasting through tiny villages and between stone walls at unbelievable speed. Like those old trophy racers, the GB500 is an air-cooled single, and even fresh from the showroom floor, the bike offered a slew of cafe racer design cues: clip-ons, wire wheels, solo seat, and tank with knee grips. Though not the most powerful or sophisticated machine, the bike garnered a cult following, and many owners got hold of their bikes via the gray market.
Steve Jones, the owner of this beautiful GB, has invested in a number of tasteful modifications that retain the original identity of this rare machine while improving the performance, looks, and handling. We will let him give you the full scoop.
Custom GB500 TT: In the Builder’s Words
The bike was in need of much TLC when I purchased it privately from a Velocette enthusiast; he had used this machine as a general runabout and neglected the maintenance. Despite this I paid over the odds for it because it was a very rare bike here in the UK; they were never officially sold here by Honda.
The first thing I did was completely strip it so I could repaint the frame and soda-blast the years of grime on the engine. While this was being done I sent the tank, side panels and front fender off to the paint shop to have it repainted in the original Honda Black/Green with Gold pin striping and new graphics.
After reading a few articles about the California models having the anti-smog pump and very restrictive exhaust system, I decided to remove it all. I sourced a custom-made Jack Batson stainless steel exhaust system, which is considered by fellow GB owners to be the best money can buy.
The removal of the anti-smog pump is very easy, but you need to blank off the front of the engine and fit rubber caps on the vacant nipples left on the Keihin Carb.
I decided that I wanted to café race the appearance to my own personal taste, but did not want to take away its original identity. I obtained some classic shrouded Hagon shocks to give it the more 60s classic look. The fairing is a universal Ducati 900ss style, but I had to make the cradle and mounting brackets.
The standard clip-ons were not suitable with this fairing and the only way around the problem was to purchase a set of Tommaselli fully adjustable clip-ons. Then, because of the extreme angle of the bars, I had to fit a remote master cylinder with reservoir. The fairing also went to the paint shop to be colour-matched.
The Rearsets are from an XBR500 and were a perfect fit, although my very old aching knees are finding them a little too extreme. The seat is a standard GB item but I got it reupholstered in calf skin and faux suede, just to be different.
The engine is standard although it spent five hours on a race Dyno trying suitable jets for the carb. It is now pulling about 45bhp at the back wheel.
She is a fabulous machine to ride and is completely at home on the fast twisty roads, with a top speed of 110mph which isn’t bad for a 500 thumper and considering that awful thing from India only puts out 27bhp.
Love the mods on your GB. I have an 1989 & 1999 models. Both are stock with low miles. I may convert the 1989 to a trackbike. The stock styling is so spot on to the clubman bikes of past.
I am interested in the modifications you made to the carburettor jet and needle settings. I did install a 52 slow jet and 158 main jet. Also a slightly shorter needle came with the Keyster kit from the US.
Also, what gain did you get from the different exhaust system which you did install.
Thanks and regards.