Have a vfr 400 nc30 racebike, was running great up to yesterday, it has gas flowed and ported heads, new valves and 3 angle cut seats, skimmed heads, full race system and carbs tuned, running total loss, ngk er9eh plugs, engine only fully rebuilt. Up to now it was starting and driving perfect all the way up through the rev range. Used the choke a few times on start up and it reved up as normal. The last few spins felt like it was slightly down on power and then yesterday shite. Still starting, but when the choke is on it wont rev past 2k no matter how much the choke is open or closed, blip the throttle and it dies and settles again. Sounds ok idling away though. Put it into gear and try to take off and it cuts out. Have to give it throttle up to 4k to get it to move and then its very sluggish up through the revs. Its not spluttering or anything, just no power what so ever, it wont pass 8k on full throttle. Battery is fully charged, checked on a battery analyzer after charging it and its full. Removed spark plugs and they looked ok, slightly damp and electrode gap was normal. Removed the carbs but didnt go near them yet. Any suggestions?

Welcome chap

What goes on with the airbox and all that jazz? Assuming it is some open?

Will it sit at idle all day long? Sounds OK?

if you roll on throttle very slowly does it pickup?

Damp plugs - get them cleaned and the tips on a gas stove to burn off the shit/

Sounds like it is being flooded...

+1 on the flooding. Double check the choke circuit as well to make sure it isn't sticking on a tad.

Hey , would like to know if you got this problem sorted , i basically have the same problem. feels dead and wont rev past 8k?

Insufficient fuel flow? Blocked breather or fuel tap issue.