I'd "like" to replace the factory case bolts (NOT the 10 big "main bolts" or any of the rod bolts.... ONLY the smaller bolts that are external) with stainless, however I'd want to first confirm what the factory bolts were (strength wise). I'm not about to go replace a hardened alloy bolt with a stainless bolt.

Metric grades are usually X.X (ex: 8.8) if anything (no marking = standard low carbon), however the factory bolts have this funny mark on the top of them (kind of looks like a squished 8 with a line under it). It's not like any grade marking I have ever come across before.

 

I don't think you will have any problems with replacing them with Stainless. The hardened ones are usually dark brown/black like the main bearing caps or connecting rod caps. The external ones that you see for holding covers and things like that are standard ones. The standard bolts that don't have a mark are in strength class 5.8.

 

Thanks. Pro-bolts (who I would be getting the stainless bolts from) says their stainless is 316 which they list at somewhere between a 8.8 and 10.x. Guess I have some bolts to order.

 

Just bear in mind that at least in 125cc engines, specially in my old NS12R the casings are silumine or some other mixed alloy, and stainless bolts have super sharp threads. Corked a few when tried to use stainless ones on that to prevent corrosion...

 

anti-seize is the key... I use it or ARP molly lube on everything...

 

Yup, Copper or tar spray here. Was young and dumb then. Now just dumb...

Propably overtightened them too...