MZ125 SM worn shims - watch out!

[crocodilemick]

Hey guys

As an experienced mechanic I was disappointed to find I had an MZ125 sm with one shim worn down by at least half a mm, and the cam lobe has also worn - worse yet the shim cracked. I thought I'd got a "bad one" with a blocked oil feed to that cam. However, I was lucky enough to find a second engine relatively cheap, I've put that in, only to discover another worn shim (not as badly this time, but it's going that way, and the cam is worn too).

This leads me to conclude that the engine has a design flaw, put it down to poor materials on the cam/shim or overall engine design (oil ways or valve spring pressure). Either way, I've got two engines that are eating shims and cams. In real terms, this isn't the end of the world, both manifolds have two valves so if I have to shave a few tens of microns off the cam lobe to get it flat again (so it doesn't ruin the next shim), that's ok.

Thought it was worth mentioning for other owners though - also, when I change the oil, I'm going take the cam cover off and drizzle a bit of oil over each cam/valve bucket, hopefully this topping up will help reduce wear.

Cheers, Mike

[DAVID THOMPSON]

i use shell rotella t 20w50
i will have a look at mine this fall and see how its doing

at 21,000 miles

and i do not run mine WFO so that may help..
dave