I figured out that i would just end up putting this engine in a streetbike. Turns out i was a bit sloppy measuring the piston to cylinder, i figured it was just worn rings. i had a 1.2mm gap in the rings and too much side to side clearance. got myself a "new" 550 cylinder, figured thicker sleeves is always good and cyl-booring might be cheaper since there is less bore to do.
Been trying to do some research about the pistons. im 99% sure they are modified 650 pistons, they questions im trying to figure out is how they would affect the engine. As far as clearance goes, they seem fine with a standard 650 gasket and the cam i got. piston is acctually slightly lower on the edge, about .4mm than a standard 500.
i tried to do some measurments of my topend, resulted in 11cc (i need a smaller incrimented syringe, and give it another go) my inletvalve goes "above" the gasketarea so i couldnt put a acrylic on there like everyone seems to do. Is this normal for +1 size valves or have mine been cut?
i filled the valve cutouts to the flat portion of the piston, ~.6 ml/cc. Then i tried to calculate the dome of the piston, alot of geomery there so i figured i would just press the dome into clay and measure that by filling it up to the edge. ~3.2ml/cc. the piston is .5mm below the edge of the cylinder wall while at tdc. This gave me ~1.4ml/cc. Didnt find any good compressed gasket charts, not sure if the numbers for ex dynoman gives of their gasket is their actual compressed? if i take one of their mls gaskets in their "middle" range of .004inches (1,016mm) that would give me ~2.82cc
11+0,6 -3,2 + 1,4 + 2,82 = 12.62cc of compressed volume. so my CR would be (142,11 + 12.62) /12.62= 12.25:1 Seems to be a bit high CR, does this sound like a unexpected value? Its a bit high since i would like to be sure i would not get any pinging on normal 95 or 98 RON. Hopefully my measurments are a bit off, hopefully. I can only speculate on that bit until i get the new syringe. As for taking hondas numbers: (498/4 + x) / x = 9:1 gives x = 15.562cc of compressed volume on an original 500 (not sure how well this match acctual measurments) just for some baselines. Perhaps i should calculate with a flat piston.
As for piston design:
You can see that the modified pistons edge is acctually lower (but on par with a cb550 piston). What about the piston design? Not sure how much material is left in the valvepockets? I have not yet measured the Squishband clearance, on my to do list. Would the design restrict flow and such? this is where im pretty clueless, the only referece i have is my -75 yoshimura catalouge where they talk about high domes disrupting the flow. "piston interference caused by a high dome configuration will result in disruption and lessening of the volume of compustible mixtre during this most critical stage of the combustion process. it will seriously impar tubulence and greatly reduce the cooling accomplished by the incoming charge" also alot of talk about getting the most amount of combustible mixture into the engine and properly burning it. The Yoshimura pistons i had in my other engine was rather flat, with some deeper valvecut out and a flat dome, i guess to compensate to the lost cr. Not sure if this is a bad idea altogether, but would be fun to get this working. I've got some Cnc friends that could help me make a blueprint to share.
What are your opinions to all of the above?
