Two months ago I've ordered Top Performaces TP 80cc cast 50mm bore/std stroke, this is the kit I wanted in the first place, but it was out of stock and I somehow ended up with Stage6 instead. Finish quality is quite better than Stage6 and all ports are factory chamfered!! Due to very little spare time I didn't have time to play with port maps, etc. but official timings are published as 186°/126°, which is very similar to Stage 6 Street Race 77cc.
TP single piston ring came in un-sealed plastic bag, don't know for sure if that means ring gap was pre-adjusted in factory but I've checked it and it was just right. I didn't care about ring gap with previous kit, which I've later found as mistake (btw Stage6 instructions don't mention ring gap at all). And their rings came in sealed bag from piston manufacturer, so they definitely weren't adjusted.
Checked squish gap and it was little over factory claimed 0.9mm. Interesting, Stage 6 has even much lower squish than claimed 0.8mm and you can feel the difference between two by turning kick starter. Now I assume that big compression of Stage 6 in combination with too tight (or none) ring gap caused that excessive wear marks around cylinder ports.
TP on the other hand has a little less power at low (around 5000) rpm, Stage 6 was almost brutal, but it runs more smoothly through entire rev range and revs higher. Honestly, to get most of it I should use at least 21 carb. I've made some 250km with TP, checked cylinder recently with borescope and it is in a TOP shape:)
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