But in my personal attempts I am not going over 860cc for the very reason you mentioned. Why try to feed a 88mm bore with small transfer ports.
I am going to do some work on a tpe cyl with 84.5 mm bore and 8mm stroker and i will post the results.
My approach maybe different then others. I want more efficient eng not the biggest eng on the market.
I will not build a 62t based motor bigger then 880cc regardless of the customers request.
But watercraft biggest nemisis is pipe design and exhaust design. No other two stroke uses the exhaust manifold designs that watercraft engines do, am watercraft make the lowest hp to CC of most 2stroke race engines.
Why??
.
900 is the sweet spot,the more time goes by and the more that is experimented on and created the more this becomes apparent. Using asymmetrical transfer sizes and shapes on the outside ports,does really help get the flow moving in a larger smoother arc,But original casts in the 85 mm bore size leave alot more room for nicer arcs on inside ports. Not to mention 85 mm pistons are much lighter,rev faster, a 8 to 10 mill long rod lightweight crank and gobs of extra torque, a triple exh port,appropriate roof angles on all ports and a pipe with a properly timed wave with water injection to keep the low rpm fuel charge from dumping and now your talkin my kinda motor.anything around 900 cc in direct drive and its all about flow with 62t,you can keep throwing larger cc pistons to the moon and not do any better than a 900 thats flowing like butter on the right pipe setup. Good bit of work being done right now with just that. Im interested to see how this project turns out for you as well.
Looking at low end hit vs top end hit from a rpm stand point is more technical than most care about. a motor that responds at the immediate same level the throttle is pulled and hits hard is "response" as well as linear . A motor that feels like it is ramping up in power a bit behind the rate the throttle is pulled and then pulls to the moon,is not a linear power curve, its a weak motor not making enough torque and power to feel nasty off idle. Most all would consider low end hit being the time it takes to pull the throttle and have the ski jump out of the water and struggle to keep pump in water,vs top end being the ski takes off smoothly and hits decent from idle then about 5 to 10 yrds outa the hole the pipe starts working and pulls your arms off all the way to the moon..rode my share of these.The freeride bpipe setups do sign off pretty quick,,but I guarantee you most all the freeriders would prefer the hit now,vs pull to the moon, now the demand for the pfp and other larger pipes is greater that many guys are building combo surf/flatwater skis and water injecting them the way the bbipe is done for easy tuning. Demand has changed tremendously.
