Motorcycle Repair: Yamaha 79 XS750SF Special, yamaha xs750, valve clearances

Question
Hey,
I've got a loud banging noise coming from what seems like one of the three cylinders when I start up my '79 Yamaha XS750.  This noise first appeared the last time I had it out at the end of '03.  I obviously didn't ride it around in this condition, but now that the weather is breaking I'd like to fix it so I can get it on the road. It doesn't seem to lose any acceleration or power when it stays running. However it tends to stall out after a bit and won't start up again until several minutes later when I guess the engine has cooled enough to turn over again. The frequency of the loud banging speeds up as you engage the throttle.  I've had several suggestions that the timing might be off, and one suggestion that the valves may need adjusted but these are coming from people who aren't experts.  I'd like to get your thoughts on what it might be, what it might cost to repair, and if it is even worth it.

Thanks

Answer
Hi Josh,

Valves normally make a tapping or ticking sound with excessive valve clearances.

A tech should hear the sounds and verify the source. There may be con rod or crank problems. The sound also may be detonation. Dunno for sure without hearing it. Too difficult to diagnose sounds on the internet.

Respectfully,
Mark Shively