Motorcycle Questions? Ask a Mechanic.
this sounds like a lack of fuel to me
This could be a lack of fuel pressure from the electrical pump at the tank.If the connections to this are corroded or damaged then the pump could stop at any time or could not be running at full speed. Check that its relay switches in and out and the relay contacts are clean and bright – replace the relay if in any doubt and do the same for the fuse,Ideally measure the pressure at the inlet to the carbs and if this is low check the pump as described and also consider changing the fuel filter as if this partially blocked this too will reduce pressure.
Fair enough my information is obviously incorrect
I'll opt out and get another expert involved