The entire engine is apart and available to inspection. The bore /stroke ratio is 1.41. This means there is quite a bit of force on that big piston area when the mixture lights off. The stroke is relatively short so the crank pins are not far from the crank centerline. This means the pressure exerted by the rods on the crank does not have a lot of leverage to turn the crank. This all adds up to some big pressures on the rod big and little ends.
One option I am looking at is having some titanium rods made. This material is more elastic than steel and it can absorb some shock to reduce bearing loads, like aluminum rods. Ti has good fatigue resistance properties. Aluminum does not.
The rod/stroke ratio is 1.79 and this is low. What this means is the rod is sorta vertical and in a position to produce a lot of downward force, with less sideways force, when the crank pin is close to TDC. Unfortunately, the crankpin is in a less than optimum position to turn the crank at this point. The rod is at a relatively large angle when the crankpin is at better position to turn the crank. All of this adds up to an engine that produces a lot of side loading on the pistons, wears the main journals on the sides, and is a bad actor under the demands of fuel combustion.
The plan is to have longer ti rods made and to install a plate between the engine and the cylinders to move the head up. The plate thickness is a multiple of the cam chain pitch so the valve timing is not made goofy. The cams, valves, and everything else need to be modeled in a much more powerful program than PipeMax to verify it will work. A rod/stroke ratio around or a bit more than 2.0 is what I need. The piston will linger a bit more at TDC to allow for better cylinder filling, too, and this is another big help. This is a long term plan and it hopefully will be in the 2017 motor. I cannot up the nitro content unless I address these structural issues.
As per the 2016 engine, the main journal clearances are .0016 to .0021 using the formula the expert gave me. The sloppiest shells I have are the white ones and they are a bit tight. The shells I am using are microbead blasted white shells. The bead impacts compress the soft coating on the inner faces and this increases the running clearance a smidgen. The blasted surface has texture and it holds oil better. The clearances are .0015 on all four journals. A bit tight, but the best I can do. This is not the first time I have done this little trick and it worked in the past.