A flat spot at 4500rpm

[mark_m]

I recently cleaned my carbs and got a nice improvement in the engine's running. The only problem I have now is as she goes over 4000 RPM the engine loses power slightly and then kicks in again. It's not very abrupt, but enough to make me very careful about accelerating as I corner. 

Any theories would be very helpful!

Thanks.

Mark.

[ProfessorRex]

Vision Stumble! Welcome friend!  Have you tuned the carbs? Have you sync'd them? if not, DO SO! That should fix the stumble!

[mark_m]

I've synced them. What other tuning can I do? I guess I'll work through the reasons for vision stumble on lucky's site.

[Superfly]

Fuel/Air mixture screws.  It takes some getting used to, but after a while, you can hear when she is in her "sweet spot".  Did you remove those screws when you cleaned your carbs? (if unsure, see Luckys site, it can explain it better.)

[mark_m]

Yup, I removed them. Thanks, I'll check them first. From lucky's site: "Adjust pilot screws to approx 2.5 front, 4.25 rear from lightly seated". I think right now I'm about 5 on both screws.

Mark.

[Lucky]

Those settings are a starting point, if they are way off then the bike can be hard or impossable to start.  how they are finally set varies greatly bike to bike. a stumble when everything else is set correctly, indicates that the screws are slightly out too far.