1980 XJ650 top end overhaul

A couple of weeks ago a customer came to me and asked if I could balance and tune his carbs as his 1980 Yamaha XJ650 wasn’t running right,

As you can see in the vid I made for the customer the carbs are balanced perfectly on my digital balancer, so with this I investigated the running issue more and discovered the hea gasket and cylinder base gasket leaking oil everywhere, well this could well of been the issue so I ordered a new gasket striped the engine down and discovered an engine coked up and a piston with a broken ring.

today we have been re-seating the valves and cleaning the ignition chambers up.

This vehicle has valve buckets as shims and they need to be kept in order so iv used permanent pen and labelled them in/ex in-inlet ex-exhust

after this I removed them using a magnetic tool and placed them on clean paper keeping them

in sequence.

Using a valve spring compressor I removed all the valve from both inlet and exhaust side of the cylinder head Paying carful attention not to loose the collet (they are arse holes if dropped)

All my valves and shim buckets in order laid out ready for cleaning, the collets are in the magnet tray for safe keeping.

As you can see these valves are absolutely shitted up and need cleaning of, the cleaner the valve the better it will open and close, the less hot spots in the ignition chamber due to carbon buildup the better the motorcycle will run and the better performance and fuel economy will be.

I removed all the carbs deposit from the valve and the set to lapping them in, while lapping them i am looking for any putting in the inclusive angle or seated face of the valve.

As you can see on this valve it has serious pitting due to age most and water getting into the cylinder, this valve will need to be refaced by an engineering company, this needs to be done correctly so the angle of the mating face is not damaged. all this so far has taken 8 hours of meticulous work and before she is done is many more hours of meticulous work. thanks for reading

Chris Beeson


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