Skorpion data, esp. tightening torques

[nickst4]

Hi People,

Sorry if inevitably this has been asked before, but does this group have a file of basic data applicable to the Skorpions, Tours in particular? I'm looking for torque settings for cycle parts (spindles, brake calipers etc) and so far have turned-up odds and sods here, and a very motley selection of numbers from other MZ lists, with massive gaps in the figures and non-specific numbers with no definition of the units used. I assume there is still no workshop manual available in English? I have Bill's German table of torque values versus metric bolt size, so I guess I could just measure each fastener as I come to it, and check the tensile strength, then look in the table.

Any help appreciated,

Nick, UK

[Bill Jurgenson]

There are very few torques you need to know that cannot be gotten from that table. Or in some cases are better taken from that table since the factory values are out of range.
The only one that comes to my mind and I have had three Skorpions, rebuilt three more and serviced I don't know how many, is the rear axle: 110mkg.
You can add the various oldtimers and Yamahas to that list as well.
In actual practice, about the only bolts/nuts I religeously tighten with a torque wrench are the cylinder and cylinder head bolts. Even the nuts on the crank and the clutch center either side are just tightened up with an impact wrench. Rear axles as a matter of course with the impact wrench. Front axles I just snug up firmly. Anything more is technically nonsense since the thick end is clamped in the fork end anyway. Much more important is not tightening that M8 clamping bolt until you have forced the fork up and down several times after tightening up the axle itself. This is necessary to let the left fork end find its correct position so that the fork does not bind. Just as important is that wipe of good grease around the 25mm thick end every time you put the axle back in. Good oil will do, but not motor oil. Use a thin highest quality bicycle (sewing machine) oil. You ought to be able to get that in the quart/liter bottle from any larger bike shop if they have a shop and are not just resellers.
Be sure to use a good thread grease as otherwise using the torque wrench is at best only good for your peace of mind. Thread grease is something special that reduces the surface friction on the thread surfaces under pressure. It is not vaseline. More important, tho, the torque values given are for thread greased with it and are only valid under such conditions. Dry or improperly greased (vaseline), threads bind to such an extent that the bolt shaft flexes torsionally like a torsion bar. In some case actually deforming. Such deformation negates the tensional strength of the steel and can cause the bolt to break under stress.
Bottom line: do it right.
Where ever possible use "Schnorr" washers.

For lots of things like the clipons, I use aluminum bolts with Schorr washers and tighten them only enuf to keep them from moving on the staunchions. Same goes for the clutch and brake lever clamps on the clipons. Old, standard racing practice: when the bike does fall over (or crashes), the clipon just moves in and/or the brake lever down and nothing much is damaged. That is one of the things I meant above with not using the recommended torques.
OTOH hand, tho there is no such thing on the Skorpion, using the OEM specified torque for upside down fork triple trees is of the utmost importance. These torques are very low and nowhere near what the thread size would dictate. If the lower clamp is tightened more, the tube is pinched and can easily bind the staunchion. That is also the reason why such forks cannot be moved up and down in the clamps or only to the extent the clamping surfaces allow. It is also the reason for those extra wide CNC-milled lower clamps with 3 and 4 bolts on some USD forks;

CNC.jpg (69.06 KiB) Viewed 1641 times

Not just to look sexy but to offer more frictional clamping surface at low torque. These re my own one-offs for my racer.
here is the stock USD fork of an Aprilia Mille which I fit into a Yamaha SZR by making a new steering post and shrinking it into the lower clamp:

tuono.jpg (69.7 KiB) Viewed 1641 times

You can see how wide even these the lower clamps are and also the raised, turned surfaces for clamping.

Just an example. The RSU fork of the Skorpion is completely carefree in this respect. RSU forks do not need anything special.

[nickst4]

Thanks Bill. When do you get time to work on musical instruments?

Nick, UK