Motorbike stuttering under hard accelaration

[Baj]

I've just had my bike back from service and noticed it still has an issue where (once the engine has warmed up enough) accelerating anything more than gently results in the engine stuttering, a little bit like its misfiring.

Is this dirty carbs?

Ive ordered some Seafoam from ebay in the hope this will clear it out, but should I just send it to the garage and ask them to do it?

Anything else it might be?

[OVER THE HILL]

If it's just been serviced .I assume the plugs have been changed ,you could have a faulty spark plug.

 

What bike is it ?

[Baj]

Surely it can't be exactly the same problem with new parts?

Its a Fazer FZS 600 '02

[Handyman]

A sharp stuttering sounds more like an ignition fault to me. Carb faults give different results. Years of experience have taught me how to instinctively recognise the difference, but I'm confounded at the moment as to how to describe the differences on here. I have known faults to be caused by "servicing". One thing comes to mind. If this happens under hard acceleration then it could quite possibly be an HT leak to earth which may not occur under more moderate throttle openings. Replacing the plugs on the service could have disturbed the HT leads and perhaps allowed one or other of them to short out somewhere on the engine. It is more difficult for the plug to fire under more extreme conditions so there is a greater tendency for the HT to short through a dodgy, weak, or corroded connection, not to mention dampness. So you see that if the ignition system is a bit below par, all sorts of firing problems can occur. If the ignition system appears to be basically sound, then another thing to check would be the coil output. This can be suspect because the coil demand rises with the pressure rise in the engine, again due to the afore mentioned extreme conditions in the cylinders. More voltage is required to fire the plugs and sometimes the demand rises above the coil output. This often happens with old plugs, garages change them and temporarily cure the "fault" (as new plugs have a lower voltage demand in all conditions) only for it to come back again later, because in fact it was a coil fault all of the time. Sorry if this post seems a bit disjointed, but I am thinking on my feet about knowledge that I haven't had to use in a long time. I hope that it is helpful.

[Baj]

Thanks for such a thorough post Handyman, really explains better a few things I have read. I feel guilty after you going to so much effort for saying that, thankfully, a good hard ride for the last hour seems to have resolved it

[Handyman]

Thanks for such a thorough post Handyman, really explains better a few things I have read. I feel guilty after you going to so much effort for saying that, thankfully, a good hard ride for the last hour seems to have resolved it

 

You are very welcome Sir.

 

I did think about about potential carb faults after posting, but seemingly you don't need anymore help in that direction.