Topic: lightened pistons etc

[kaceyf2]

Hya there folks,looking through old posts and spot mikes mention of reciprocating weight and more importantly, "the loss of" being good.....just wondered if anyone had used any form of "slipper" pistons OR even cut down their own ( and then weighed them against each other of course on a set of decent scales) SOMEONE must have had the stones to? NOw that I finally got some cash IN (instead of pissing OUT me pockets to the governments many devious ways of having it off me) I have finally got back to rebuilding me bike! The porting has now been finished,and looks sweet as.That got me to thinking big-bore etc.........
whats your thoughts guys?

[supersport_CB400F]

Roll another fat one 

[scondon]

     Glad to see ya back on the forums, kaceyf2. Now there's at least TWO guys who see engine bits in their sleep and obsess over every detail

    I don't know anything about cutting pistons or using "slippers. I've been pretty happy with the 836's "as is". Mrieck says he can lighten and polish the stock rods, and you can also get lightened rocker arms. These mods may help with those pesky "reciprocating weights".

[MRieck]

Trying to lighten pistons is tough. You can have a pile of aluminum sitting there and only lose 3 or 4 grams off a piston. Light pins are nice. Yoshimura used to supply nice, light tapered pins with their kits- good stuff. Slipper pistons relly don't save weight...they cut down on friction. Unfortunately they don't control oil well which causes detonation and smoking. Detonation can be controlled by using designer fuels but oil consumption remains a problem. Significantly lighter rods are nice too and are easier on bearings but you are talking Ti which is expensive or aluminum which is not as durable.

[Big Jay]

It would be very tough to get any weight out of oem pistons. The little you could get would be of no benefit.

Jay

[kaceyf2]

thought it would be That way! ha, Oh yes, while I remember just seen an add in Classic bike mag in UK for 5mm valve conversions for cb750, that means lighter springs which gotta be good especially on my ridiculousely heavily oversprung sohc f2. You wanna see the dints in them valves heads...craters....D,degans (dresda) was featured in a recent article next to pics of his 4mm valves, and the springs you could coil-bind with no effort with your pinkys..and regularly revs up to 14 thou on the track!...gotta see if the "elephants foot" rocker tip that he deseigned to eliminate incorrectly struck valves ( and there fore vibro stressed valves) could be got in metric sizes!
getting rid of what adds up to thousends of pounds of  (excess)   reciprocating weight out of my valve train would suit me sir.....PLEASE!

[MRieck]

thought it would be That way! ha, Oh yes, while I remember just seen an add in Classic bike mag in UK for 5mm valve conversions for cb750, that means lighter springs which gotta be good especially on my ridiculousely heavily oversprung sohc f2. You wanna see the dints in them valves heads...craters....D,degans (dresda) was featured in a recent article next to pics of his 4mm valves, and the springs you could coil-bind with no effort with your pinkys..and regularly revs up to 14 thou on the track!...gotta see if the "elephants foot" rocker tip that he deseigned to eliminate incorrectly struck valves ( and there fore vibro stressed valves) could be got in metric sizes!
getting rid of what adds up to thousends of pounds of  (excess)   reciprocating weight out of my valve train would suit me sir.....PLEASE!

I have the Kibblewhite 5mm conversion kit in my bike. I was one of the first...if not the first,,,,to run it on the street.

[crazypj]

I have a brand new old stock CB 750 piston in front of me (0.75mm OS). Its difficult to get any significant weight reduction but it is worhwhile to do some mods to cut down friction. You will need a lathe for the main mod and a lot of patience to carry out the reprofiling inside the skirt.
Unless your going to be vintage racing and need the edge, it isnt worth the effort.
PJ