Saturday October 18th 2025
Saturday October 18th 2025.
It was a busy workshop session with lots going on…
Yamaha TX500…
For those of you that don’t know much about the TX500 my friend
Copilot has put together the following…
Yamaha TX500: A Forgotten Pioneer of Four-Stroke
Innovation
In the early 1970s, Yamaha made a bold move to expand beyond
its two-stroke legacy with the introduction of the TX500. Launched in 1973,
this motorcycle was a technical marvel for its time, featuring a 498cc DOHC
8-valve parallel twin engine. Yamaha’s goal was clear: to challenge the
dominance of British and European four-stroke twins with a machine that
combined performance, refinement, and modern engineering.
The TX500 boasted a counterbalancer system to tame
vibration, a five-speed gearbox, and a top speed nearing 110 mph. Riders
appreciated its fuel economy, which hovered between 40 and 55 mpg, and its
sporty character. However, the bike’s promise was undermined by reliability
issues, particularly overheating and valve train wear, which plagued early
models and dented its reputation.
In 1976, Yamaha rebranded the TX500 as the XS500,
incorporating mechanical improvements to address its flaws. Despite these
efforts, the bike never achieved widespread acclaim and quietly faded from the
spotlight.
Today, the TX500 is remembered as an ambitious but troubled
step in Yamaha’s evolution. While not a commercial success, it laid the
groundwork for future four-stroke models and remains a cult favorite among
enthusiasts who admire its engineering daring and unique place in motorcycle
history.
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| A TX500 as it looked back in the day. |
On this particular Saturday Phil R, Dave and AJ worked to continue rebuilding the engine. They assembled the cam chain drive gears in their correct positions, and then went to fit the cylinder head. Phil noticed that one of the Dowels was missing. For those not familiar with dowels my mate Copilot tells us…
In this particular instance the dowels are hollow and fit around the cylinder head studs. AJ intended to machine up a new dowel so that the cylinder head could be refitted at a future session. At this stage we were still facing the issue of the awkwardly cut cam chain. Replacement chains were extremely rare (Even rarer than Dragon’s poo!) and very expensive. Would we find a replacement – our search continued.
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| The team at work. |
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| TX500 Barrels back on. |
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| A little induction induced heat sometimes works wonders |
Honda CBR1000F…
When the bike was taking outside to start it up and warm it
up another fault reared its ugly head.
When Chris attached the temporary fuel tank fuel began dripping off the
righthand (No 4) carburettor. Once again hands were flung in the air. As the
leak was relatively slow Graham decided to at least start and warm up the
engine. Having fathomed out what needed
to be pressed or joined back up again and what needed to be pulled in, the starter motor whirred into life and the
engine started. At first the exhaust was
a little smokey but as the engine ran and warmed up it cleared up. Concerns over other issues in the
carburettors evaporated when the engine started to get hot and Graham found opening
the throttle wide in an instant at tickover didn’t have any ill effect. The engine cleanly and very quickly picked
up speed sending the rev counter needle towards the end of the dial. With the
engine off, it was time to take a closer look at the source of the leak. Shining a torch between number 3 and number 4
carburettors revealed that the leak appeared to be coming from where the fuel
feed fitted between them. As soon as the
fuel tap was turned on, out came the fuel.
As soon as it was turned off the leak stopped. Was it a hole in the fuel pipe? By now Chris was well versed in removing the
bike’s carburettors. With a little help
from Graham to get the various cables detached the carbs were soon on the workbench.
As Graham had to leave early Chris
worked to try and cure the leak. But replacing the wire clip securing the pipe
to the tee-piece with a jubilee clip did not resolve the problem. Could it be
that the O-rings on either end of the tee-piece had shrunk or failed, we would
have to find out.
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| What would it take to overcome the fuel leak? |
Honda 650 Vigor…
Mal and Dan worked on the bike. The front wheel complete with its new tyre and
inner tube was refitted. They had a go at rerouting the troublesome throttle
return cable and when last seen were still puzzling as to why it didn’t want to
fit? Mal tried cleaning off the corrosion on the bulb housings on the rear
indicators. However because they were cheap
aftermarket ones and in very poor condition Mal decided to order a new pair
which was probably going to be a better long term solution. They were just waiting for the correct rear
brake disc to arrive and then it would be time for an oil change and tweak of the
tappets and the carburettor adjustment ready for an MOT. Just in time for the winter, oh well at least
it would be running for those drier winter days.
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| Front wheel back in the 650 Vigor complete with new tyre and tube. |
In other news…
Seimon and Ian returned to capture more images and footage
for the promotional video they are working on as a way of promoting the good work
the club does. Ian told us that he had done his own research and that West
Wales Motorcycle Club was the only club of its type he had found in the UK, with
just one other similar club in America. It
was a reminder of just how unique and how important the club it for its
membership and their mental health in general.
The reason that I had to leave early on this particular
Saturday was that I wished to see the ‘mobile museum’ that Seimon had developed. Harry and I went along to Cefneithin near Cross Hands to take a look at
it. It was hoped that with a little
help from our members we could create an oldy weldy workshop tableau to help
promote the work we were doing. More of
that in future blogs.
As can be seen below Andy continuous his festidious work to restore the good looks of our Z250 tail piece.
Finally, does anyone have the slightest idea what club member Heinz was trying to achieve here?
