I have removed the oil pump and reservoir from my bike and at the same time installed an inline fuel filter and cleaned the carbs all after doing a topend rebuild.

The bike will not rev under load now. During idle it sounds crisp and responds great and will rev but under load it struggles to rev past 4k RPM.

I did a bit of searching on the forum and could only find that an old battery may be the culprit so changed that for a new one with no change to the revving problem. After that a changed to fresh plugs just in case but this also did not fix the problem.

Does anyone have any ideas what it might be, before I strip the whole thing down again?