13-03-12, 11:37 AM
I've found valve clearances on the FZS600 to be amazingly stable. Check them by all means, but don't be surprised if they're in spec... mine still were at three times that mileage.
Nor would I expect low compression to result in those symptoms: reduced power especially at lower revs, difficulty in starting, backfiring (or even backfiring through the carb in the case of inlet valve leakage) would be more likely. If your tester has a valveless adaptor to get it to suit the small plug holes on bike engines then it will give a low reading... they're more useful for picking up on differences rather than absolute measurements.
A new set of plug caps may help, some NGK ones cleared an intermittent misfire for me, but it sounds more like the problem may be the carb slides no longer moving smoothly due to wear. My current set are giving similar results: a massive flat spot with plenty of power available again once you've coaxed it through. It's easiest to provoke by snapping the throttle fully open from cruising at 70-80mph, the sudden difference in pressure jams the slide against the grooves in the carb body and the diaphragm doesn't develop enough force to overcome the friction. Dri-Slide or even applying an 8B pencil to the grooves will relieve the problem for a while, long enough to prove the theory anyway.
Nor would I expect low compression to result in those symptoms: reduced power especially at lower revs, difficulty in starting, backfiring (or even backfiring through the carb in the case of inlet valve leakage) would be more likely. If your tester has a valveless adaptor to get it to suit the small plug holes on bike engines then it will give a low reading... they're more useful for picking up on differences rather than absolute measurements.
A new set of plug caps may help, some NGK ones cleared an intermittent misfire for me, but it sounds more like the problem may be the carb slides no longer moving smoothly due to wear. My current set are giving similar results: a massive flat spot with plenty of power available again once you've coaxed it through. It's easiest to provoke by snapping the throttle fully open from cruising at 70-80mph, the sudden difference in pressure jams the slide against the grooves in the carb body and the diaphragm doesn't develop enough force to overcome the friction. Dri-Slide or even applying an 8B pencil to the grooves will relieve the problem for a while, long enough to prove the theory anyway.