hornet 99 running issue

[steven_191]

So here's the full story.

Did a partial strip down at 15k miles for a service. Changed the oil and filter, checked air filter but was clean (k&n), checked plugs and posted here which were all fine (I have new ones but not installed yet). I checked valve clearances but following the manual which told me to loosen the chain cause the cams to slip so I had to reset and check the timing which is fine now.

I had an issue after first starting up. If I open the throttle it bogs down and dies. If I get it in gear and start rolling to stop the engine from cutting out, after ~4k revs its fine. You can open the throttle in neutral and it does t bog.
Because of this I starting stripping the carbs. Got carbs 3 and 4 apart and they looked brand new (on the inside).
Put then all back together and did a rudimentary balance which did make it run normally again.

So the issue really I have found is that after a bit of warming up and rolling about it sounded like there was more rumble from the engine that before and sort of like it was firing extra ignition? Then after a while it was ok. Once warmed up properly it doesn't bog down but if your in neutral and you open the throttle it'll rev quickly to about 6k, slow down, then rev quickly above that. So is that a dead spot?
It has the k&n filter and an acropovic can but I don't know if its ever been tuned. I Intended to get it tuned at the very least to make sure its set up, not for power gains.

What do you think about the odd rumbling which then went away or the dead spot around 6k if that's what it is. I must admit I have never sat on the bike and whacked the throttle open before the service so can't really compare. Cheers.