Originally Posted by Torque Monster Ask Carrillo if they have the KTM 530 rod in the system, only difference as you know is the wrist pin size. May speed up getting something made for you if they did. |
Sure did ask them mate, they weren't sure about the big end 0.D. they told me that a hardened sleeve was needed and concerned that the material left was near or less than .200". But it's cool Travis from thumper racing hooked me up with a aftermarket rod kit, the bike is back together and I just enjoy riding it when I can and looking at it when I can't ride it
So my theory in regards to the big end roller track flaking out at the top side has a fair bit to do with the work of Mr Irving and his incredibly informative publication "Tuning for speed". In there he explains that the big end roller assembly is the most heavily stressed component, due to dealing with acceleration deceleration and the change rotaional direction of the big end relative to the crank pin as the rod accelerates up from bdc and then decelerates through the tdc dwell, then acceleration away from tdc in the opposite relative direction.
This becomes a real issue if the roller cage I allows to rub on either the crank pin or in this instance the roller track of the big end as the soft material I the cage will wear the pin or big end faster than if being rubbed by material of the same hardness. It makes sense to me as I had galling all round the o.d. of the roller cage ( didn't photograph the cage

please if you have a blown up 70 degree bearing cage post up a photo please !) and in my work as a diamond driller I use soft compound drilling tools for rock formations of a high hardness and vice versa.
There is witness of the cage rubbing the pin in the photos on the last page, the damage to all 3 70 degree rod I have seen are in that area where the swing of the rod changes direction and so the rollers and cage must as well, if the inertia is greater than the friction between the rollers and track then there will be sliding or skidding at that point as well just to complicate things.
How to fix ? A cage of slightly smaller od with hard chrome plating on the bars of the cage to resist the rubbing action I would suppose.