JBOT - none of those questions have anything to do with the ability of transfer flow, but I'm happy to answer. HPI inner rotor, 2.1mm BTDC. MLM BK100. 17x42. 2 rings on stock piston, so 1 dykes, 1 regular. I have ported the cylinder slightly and feel the transfers are "pushed back" as far as possible w/o welding the cased, I'm already getting into the bolts deeper in so anything more at the deck would just bell out at the top. I'll list the port numbers later.
Adam Smith - not talking max RPM before the engine scatters, talking about the ability of transfers to flow air.
Chöschi21 - I wonder what their porting looks like.
To add a little more to this here are the area numbers I came up with for certain things, I assume these would all be listed as millimeters squared
Carb and Intake manifold 452
Intake port 510
Exhaust port 600
I'm pretty simple minded when it comes to some of this but when you have a smaller port like the transfers the port velocity is higher than a larger port so depending on the size of the port vs port velocity you could have larger or smaller ports at different velocities that flow the same.
Port durations in degrees
Main transfers 130
Auxiliary transfer 118
Squish is at 1mm.
This is the same cylinder that hit 77.6mph in 2014 that has been massaged a bit. At that time I was only spinning it to 10,700 relying on the torque to pull the gear. Now I'm trying to get it to breath better in hopes of getting in the 80's. I'm kinda working against myself here because I have gotten more RPM out of it since before but haven't put a load on it with more gear to verify it pulls the gear to a higher RPM. I should do that to see if it breaks 80. But, for street use and everyday practicality it would be nice to spin 14k to have a wide power band/speed range. With 17x42 its in the low/mid 60's but 70 would be ideal. Still has great takeoff at that gearing.
This is getting long winded. I think I need to gear up and see how fast this thing goes then mess with RPM. I'm convinced the transfers are the issue but still appreciate any input. Talking gets the ideas flowing.
I'll post a picture of the transfer to cylinder from my phone, can't figure it out on the computer.