No need for race springs in a stocker.
Fresh +0.25mm pistons will run better with a fresh head.
Check if valves wobble sideway in guides when wiggle it with fingers holding the "disc", lift ca 10 -15mm.
You should not feel a lash, a softness ok.
Exhaust guides will go bad first.
A high power engine can run very smooth if carbs and ignition are tuned OK.
Both my bikes have Dyna-S ignition and advancer springs shortened.
I had points on my K6, but dyno graaf looked not good at higher revs.
K6 970cc - 107.5Whp (done twice on dyno 2 weeks between runs),
K2 748cc (+0.50) - 58Whp.
If you want more power, higher compression pistons with deeper valve pocket is a must. Then ready for higher lifting cam.
Or cheap pistons from Cruzinimage for a little bit more compression only. 836cc or later K7 (392) pistons in an earlier engine. My K2 has +0.50mm CI K7 pistons only. 58+Whp on dyno. But still rather tame, it take time between gear shifts during WOT.
An 836 with ported head, bigger in valves and modest cam still using stock carbs is a huge difference.
Better pistons and hotter cam will bring ported head since the old head might have worn valve guides, exhaust especially. If engine has done over 50- 60.000 km, very likely.
Restore a stock head replacing guides, valves and cut all seats is one big step needed anyway.
A port job at the same time will help.
If you plan to use cam with higher lift, the guides must be replaced with new that is sunken deeper in the head.
Either stock guides with a new cut stop groove for lower placement or CycleX shorter iron guides.
If not, engine will drink lots of oil when valve keeper groove will enter the guide seal sealing lip.
Foto of an oil drinker with stock modified guides below.
9.6mm between seal and groove. It was sunken but not enough. (Measured an old stock head, ca 9.2mm)
It need running lash + at least 0.5mm, my head >11.3mm
My cam lift IN ca 9.8mm at running lash.
At higher revs valve can go a little deeper.
This was found rather soon so the shop could remove guides and install them even deeper and back in again. Guides marked so they went back in exact as they sat.
Improve power need more engine jobs.
Maybe a complete restore of the engine is needed? Total teardown, check all chains, tensioners probably in need of replacement. New clutch etc. Rebore with new pistons, cheap Cruzinimage or better.
Forummember Don R has recently got a set of NOS 812cc pistons he might sell?
Find another old stock cylinder and bore it to 64mm.
Photo of the oil drinking seals when keeper grooves enter the lip.
Aftermarket "race" valves should have a shorter groove. -1.5mm would help.