‘Four valves needed replacing – it wasn’t going to be cheap’
Bodged valve job leads to costly repair
Modern engines are precisely engineered marvels of science and technology, so having your unqualified mate attempt to alter your valve shim height with a bit of sandpaper is probably not the brightest idea.
Nonetheless, when spannering surgeon Daniel Wadsworth came across this Yamaha YZ250F, that’s exactly what had happened.
The story goes that after buying the crosser secondhand, the owner had managed just one ride before it cut out and stubbornly refused to restart. After the owner had the bike recovered to the workshop, Daniel got to work.
“Initially, I performed a compression test which showed zero psi,” he said. “Then after removing the head and checking the valves,
I found there was no clearance on any of them.”
After his foray with the feeler gauges, Daniel set about investigating the bike’s former life, discovering that its past owner had let his mate have a crack at bodging the valve shims.
The Yamaha already had the smallest size shims fitted, but rather than replacing the worn-out valves as was needed, the havea-go hero had tried, and failed, to create even more clearance by sanding down both shims on the inlet side.
With all four valves in a bad state and needing replacing, it wasn’t going to be a cheap fix. Daniel said: “They were £126 each, so after labour the total cost came to £750.”
After lapping the new valves to match them with their seats, Daniel reassembled the motor, dropped it back into the frame and with that, the crosser was back up and running.
Owner of DSW Servicing