I have had to sort out so many bikes with fueling issues in the past. Sorry not sure your spec for needle height, BUT the needles are mainly midrange and cruising. Stock needles often dont have adjustability or washers, just a nylon spacer or something like that that sets the needle height. Maybe its a jet kit??
Heres my test for a topend running issue:
1. Change spark plugs no matter how good they look unless they are <6months old.
2. Check coil leads are connected, pull off and push on a few times.
3. Check charge system of bike - start and put on high beams, blinkers etc and none should really dip in brightness. Get a volt meter and test battery charge while engine running - should be 13-14V. This should not really affect your topend but can point to something more serious before playing around with fuelling.
4. Remove the washers and your jetting should be leaner in the mid-range. Worst case they will make the engine run flat then you will get a good surge of power as the main fully kicks in - Normal.
If the engine starts to sputter, bog down with no power & spurt out brown exhaust smoke - your main jet is likely to rich or its an ignition issue (coils).
Remove airbox lid and make sure air filter is clean - ride and see if its better - if no change its not fuelling issue and must be ignition related (coils or leads), or possibly (but very much doubt it) a CDI issue.
Coil troubles are funny because they get worse with heat as your engine warms (just like jetting) and at all kinds of revs, so can replicate fuelling issues.
Float height can cause some troubles but rarely at top end, more so cruising at 2.5-4k rpm. Pilot jets are idle and up to 3.5k rpm cruising, Needles are 3.5k-6k rpm, mains affect all throttle openings but usually >6k rpm
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