:doh: wow vary informative

:doh: wow vary informative


Just try to keep up!

You need to read between the

OK - I think the bot probably meant to link to this video....

IqM1_p9Q6nM

I can't believe Kawa has moved up to a 400. I bet they will start making 1000's and 1400's soon.

It's clearly a homage to the greatest bike ever made, the EX500 Ninja. Too bad they skimped on the engine size.

Makes no sense:

"Engineers were able to cut the weight of the pistons by placing oil jets that spray the underside of each piston as it travels up and down."

Understandably, writer was probably rushing against deadline to make his $38 in profits while wrangling with his diarrhea kid.

Sure it makes sense. Cooling pistons by oil jet is quite common. A lighter piston needs it, because there isn't as much metal there to use as a heat sink. Flip that around: if you design the oil system to spray the underside of the pistons so as to cool them, then you can make lighter pistons. Therefore less reciprocating mass, therefore higher rpm and faster acceleration, etc.

From https://en.wikipedia.org/wiki/Internal_combustion_engine_cooling


Only the fixed parts of the engine, such as the block and head, are cooled directly by the main coolant system. Moving parts such as the pistons, and to a lesser extent the crank and rods, must rely on the lubrication oil as a coolant, or to a very limited amount of conduction into the block and thence the main coolant. High performance engines frequently have additional oil, beyond the amount needed for lubrication, sprayed upwards onto the bottom of the piston just for extra cooling. Air-cooled motorcycles often rely heavily on oil-cooling in addition to air-cooling of the cylinder barrels.

No no no... that oil spray is for additional thrust upwards. It... uhhh... increases the speed of the compression stroke! yeahhh that's it.

Sure it makes sense. Cooling pistons by oil jet is quite common. A lighter piston needs it, because there isn't as much metal there to use as a heat sink. Flip that around: if you design the oil system to spray the underside of the pistons so as to cool them, then you can make lighter pistons. Therefore less reciprocating mass, therefore higher rpm and faster acceleration, etc.

From https://en.wikipedia.org/wiki/Internal_combustion_engine_cooling

Yeah, I've always notched the con-rod to squirt oil under pistons. Just never used it as method to lighten a piston. I wonder what the 400 piston weighs... or what it's made of... cast? Forged? Hypereutectic?

https://www.thesamba.com/vw/gallery/pix/1318823.jpg

Okay, so I know you're kidding but to be clear... spraying oil doesn't cut the weight of the pistons (duh). It allows the engineers to use lighter pistons in the first place by improving cooling.

Yeah, haven't been able to find a single forged lightweight piston for 250 engine that's lighter than stock that requires oil-squirting. JE, Wiseco are cast & machined with excess edges and heavier than stock. Wossner, Arias, Arrow or Mahle can get me desired piston, but at $1600-2500/pr...