Taffy said:
you won't be going 'up' to a 32mm big end - you have a 32mm big end. I use the prox stuff and while the quality is Ok I'm not sure you should go down the chinese route for yours.
Haha! What a mistake! Can't blaim the spell check for that!
Taffy said:
try alpha bearings in the UK, they have high quality stuff and use a silver coating which helps with lubrication and wear.
Thanks for the tip!
Taffy said:
the 35mm big end will handle everything better even though you lose 16cc. however the rod ratio is quite short on the Husaberg, not sure you've read up on it but the rods could have done with being longer. If I was starting again tomorrow I would take 2mm off the crown of the piston and add it to the rod centres. 137 or 138 something like that.
I agree. Increasing rod/stroke-ratio will reduce piston to cylinder wall contact force and allow higher piston speed, it will improve the force transferred to the crank and increase the degree around the crank revolution where you have effective force from the combustion. I believe the weight is the only bad thing connected to increasing the rod length.
Taffy said:
I put the 35mm big end in the old crank and made a 666, well two 666s and have heard nothing back at present. but as I say, get the rod length up 2mm if having them made and get the piston crown edge down from 14.4 to 12.8 or so.
666cc you say? With an offset 35mm pin and a 32mm rod, or how?
bushmechanic said:
I haven't seen a nice light piston over 100mm yet but Im sure you could knock one up
I firmly believe at this point the way to "cure" the main bearing issue is to prevent the crank spreading at all and use preloaded annular contact balls, you might need to lighten the crank though and that looks like a Pain in the rear on the 644. if you used the annular balls you could use a 32mm big end in a "stroked" 628 crank (82mm) then you keep the light rod, the long stroke and you can lighten the crank easily.
perhaps get in touch with Tom Miller he is very helpful and knows his stuff regarding the annular balls,
http://www.cut7.com/
Take a look at the 106 mm pistons "Pistal" is making for the 1198 Ducati! Very nice work! Unfortunately their minimum order for custom pistons is 10 pieces... Wössner has some nice forgings that a handy man can mill out.
In my case I think there will be a need for both reduce the crank flex, and use better main bearings. Angular contact bearings have been std in Ducatis for some time now. Put together with 0,15-0,25mm axial press fit for the crank. With alu temperature enlongation, I believe the will work at +/- 0,00 mm when in operating temperature. A friend, with a classic side car RR, has put those type bearings in his Weslake as a last resort.
This year I'll just put it together as it is, and use normal ball bearings, replacing them after 3-4 hours. A fun plan would be to:
-Use a 35 mm pin and 80 mm stroke
-Use a bigger steel liner (less blow-by) together with a 102-105 mm piston (654-693cc) with the piston pin located as far up as possible.
-Increase rod length to 137-138 mm (Carillio)
-Fit angular contact bearings
But keep it to yourselves! If the Mrs's find out I'll be in big trouble!