99 fzs600 lumpy idle, lumpy low speed

[unfazed]

Thank you for helpful replies:) Based in North Devon. I'll double check the chain but within tolerance last time I checked..

Changed my sparks today....this was no 3 spark!!!!!



The coolant manifold is DIRECTLY above no 3 spark. Wondering if I have a small leak that's allowing the coolant to pool. I'm hoping that piston isn't shot to hell!!!!

It is not coolant, the issue is caused by a blocked drain hole for plugs 3 and 4. when you removed the plug the the rust laden water wet the plug as it was being unscrewed. The build up of water is causing the plug cap to to arc the giving the rough running.
It happens when the bike is left on the sidestand in the rain and rubbish gets in there and blocks the hole.
You will see the hole on the centre of the side of the head. There is one on both sides.
Number 3 is more prone especially if left for long periods on the side stand outdoors uncovered in all weathers.
The hole extends from the side of the head to plug 4 and the three is drained past 4.
Poke it out or try a blast from a power hose once it is clear wash out the area.
Might want to remove the plug cap and clean it out if it is still slightly rough change the plug caps.

[Gabrael72]

Completely agree with the post above, I took on my Fazer a few years ago and decided to service it (not having much history with it) and number 3 plug sheared off in the head, turns out the previous owner never changed it (only the others) because it had rusted in there due to the drain being blocked, ended up having the head off and drilled out then helicoiled (£450 later,) a good piece of advice would be to take them out and put some antiseize on the plug threads (not too much towards the nut end of the thread) just to help prevent this possibility in the future, also make sure the drain hole is clear too!