interesting for sure...... roberts engine moved right along.......
....nothin wrong with that....the aqua engine will gain way more punch with a standard back plate.. the pto pin would need to be machined or ground off,,, the cvrm back plate will fit the aqua if the o.d of the back plate is turned down a bit..... its actully upsetting to see manufacturers move away from a design,, just to try another... instead they should make what exists better be refining the design... i was sad to see the aqua go.. cause with the right work they really do rip... ive found the crank end of the rod to be the culprit in 80% of the rod and crank breakage issues ive seen..... the one mistake i found in the aqua rod is the oil hole......its all wrong imho... the hole is drilled in the bottom of the rod in a vertical position to the crank....seems well and fine,, but do you think there is a puddle of fuel in the case at high rpm... im thinkin no.... lack of oil to the crank pin,,heat happens,, the bushing in the rod swells,,puts a ton of friction to the point of binding and badda boom........the rod siezes to the pin and swings the piston like a hammer and breaks the rod or crank...
the answer to this is cross drilling a hole into the rod at an angle,,from the top of the big end into the center of the bushing,.. install the rod with the hole you drilled facing the window of the crank... now it has no choice to be well lubricated as the fuel passing through the crank window splashes into that hole on every revolution... it also doesnt hurt to clearance them a couple tenths of thousands....
the rear transfer passage in the case needs to be opened up..the cases were machined short of going all the way through... that passage is near blocked off with the sleeve in the case.... back plate can be ramped in that area also..
ive done alot of testing with these engines along with bill,,, and with the right prop,,and pipe they are fast for rtr's