5-6 k rpm is nothin to some setups, Most high rpm pipe set ups (any other pipe then circuit, estroil or stock) need 8k+ rpm.
Stock hp cylinder or feeblely/poorly tuned kits need near stock 1,700-1,900 rpm engagement RPM to takeoff.
The only problem is with that low of a engagement speed you will stall on a big hill and you'll have to pedal up the hill instead of the clutch slipping you into powerband powering you up the hill.
I did pretty much every puch kit under the sun with every pipe available and with a stock OEM clutch (2or 3 shoe) kickstart springs 3-3 1/2 turns in from flush were the least I could use for Best engagement rpm. Most cases especially for higher RPM pipes kickstart Springs along weren't enough I needed to lighten the clutch shoes and or use a brace.
You must be doing something wrong, using aftermarket clutch or shoes, or be using lightened clutch shoes for kickstart springs to be too much for you.