TOPIC:

Miller bored out his Honda/Davidson CB 750 to 1015' The barrels were so thin he had to have them built up so they wouldn't weep. That Chopper thing would walk from my Z1b1000 until I got some cams, then it was rider against rider.
Question is how much do you want to spend when you can always get a bigger bike?
Steve

Here is a brief explanation of modern skirt design including skirt cam. The skirt area is not perfectly round, is not the same diameter from top to bottom, and varies in thickness. The skirt is crucial to piston performance, and is a fairly complex bit to design and manufacture. I bet even that old Indian would have gone faster with a carefully designed and manufactured set of pistons.

blog.jepistons.com/maximizing-horsepower...piston-skirt-shaping

SWest wrote: ..................Question is how much do you want to spend when you can always get a bigger bike?
Steve

Excellent question! For example, given enough funds one could use (make) a 750 turbo engine and with appropriate mods turn it into a monster such as one in the link below. Ed

www.750turbo.com/forum/viewtopic.php?f=9...f51c1956060ca2366de2

daveyg wrote: Not sure what cam in the skirt you’re referring to though.

Pistons are not round.

If you want to build a head turning motor to prove your talents as a fabricator why not just
do something like this ????
Dave

FRIGHTENING
Steve

650ed wrote:

SWest wrote: ..................Question is how much do you want to spend when you can always get a bigger bike?
Steve

Excellent question! For example, given enough funds one could use (make) a 750 turbo engine and with appropriate mods turn it into a monster such as one in the link below. Ed

www.750turbo.com/forum/viewtopic.php?f=9...f51c1956060ca2366de2

Then boys across the pond making big hp.

Had some free time today on my day off so started messing with the CAD work on the new piston. It should get me a tiny boost in compression (added .020” to the highest point of the dome) the new sleeves should be here tomorrow! I’m going to hard anodize the piston from the oil ring groove up, and will cerakote the skirts with microslick low drag coating. The first few pics are the ‘blank’ from which I will create the custom castings, the last 2 pics are once I finish the machining work on the piston.

Down the road I may go the Allen Millyard direction eventually, or maybe even the Ian Drysdale direction. But I think I’ll cut my teeth on this project, exactly as I’ve described. Keep stock stroke, stock crank, stock rods, and just ridiculous bore haha. Maybe I can get some good RPM out of it if I can blend the head runners well enough to get some decent flow characteristics.

As for the ‘not roundness’ of the piston, it’s actually more like conical, tapered, and only by about .015” diametrically at the bottom of the skirt, so I will just cut my casting on the lathe, and give it about 1 degree of taper. Plus the cerakote will add about .0015” to the skirts as well. The rest will be fixed by my changes to the piston shape itself, to get it more modern, eliminate all the excess piston drag. We’ve come to the point with modern pistons that we have learned that there’s no need for a skirt under the wrist pin, aside from sufficient material to allow proper strength when ‘pulling’ in intake mixture.

If the results of my 932cc super big bore are not sufficient for my fun, I may try supercharging it. I’ve played with turbos a few times, and turbos plus carburetors usually don’t play well, and I don’t like fuel injection enough yet to build my own from scratch a la megasquirt so if I get to that point I will hunt down a small (Aisin or the like) supercharger instead and run that with a huge (for a bike) draw thru carb feeding into it.

Well my donor jugs arrived today and unfortunately in my excitement and haste, I broke one of the sleeves pressing them out. Good thing I can get 4 more for about $40 hahahaha. Anyway, here’s the requisite comparison photos. The factory 750 liner actually fits INSIDE the new liner. The new liners are 81mm outside diameter, so they’ll actually be ever so slightly touching once installed at the 750 bore spacing hahaha! This is gonna be great!