So, I've done some more research, and measuring on my sets of sleeve, piston and ring. What I have found out is that HPI's stuff are way off on what seems to be considered normal measurements on piston play, piston ring gap etc.
I also noticed heavy scratching in my first sleeve, mainly located directly above the exhaust ports, see photo below. Unfortunately i didn't check for burrs before I honed. But I have now checked the second sleeve, and it does have burring on the inside edge of the exhaust port.
I also took a picture showing the piston ring gap. Or perhaps I should say the piston ring barn door opening... Normal gap for a cylinder like this is 0,1mm, I measured mine to 0,35.
These issues could be the result of a sleeve with a too large inner diameter, it will give to much piston play and to big piston ring gap. Burring on the ports is another issue with the sleeve. Clearly, HPI are having quality issues here. In my opinion they now owe me two sets of piston, sleeve and ring. But they just turn me their back. Which is why the two new cars I bought the other day were not HPI-made.
In any case, I honed the original, first, sleeve, with which the car basically won't start at all any longer, at best ignite once or twice, with basically no compression at all. Having honed it so all scratches have disappeared or at least cannot be felt/get stuck in with your nail. One big can still be remotely felt but not get you stuck. It widened the inner diameter some 0,05-0,1mm, unfotunately also increasing the piston ring gap somewhat. Which made me realise that it may not run at all, just because of that.
In any case, in it went, the honed sleeve with the old piston and ring. Choke on, ignition on, a couple of pulls and it ignites once. Choke off and more pulls. Nothing, nothing, nothing. Out with the spark plug. All wet. in with another one, dry, with quite a big gap. Second pull and the car starts and runs for 5 seconds. WHAT? That's a BREAKTHROUGH! A few more pulls and the car starts again, manually increase the throttle a bit to keep it running, and it keeps running. after 30 seconds or so I release the throttle to idle, and then it dies within a second or so. Conclusion: the honing has made a tremendous difference, despite the larger piston ring gap. The engine needs to be broken in "again", and then we will see if I can get some decent power out of it this time. Unfortunately I am not too hopeful. A new piston ring with a tighter gap would be a good thing. But I guess HPI doesn't sell piston rings to be manually tuned to the optimal gap?
Of course the piston ring has some damages to, as a result of the burrs. But I didn't see any way to fix those, other than to make sure there were no protruding burrs or similar.
