Cut the end off a 1/2" drive socket, a 16mm wrench (a 5/8" might also work), and weld them together. You'll probably have to grind the wrench down a little to fit. Use a 12 point wrench as it provides more options on alignment. It gets tight around the frame, especially near the battery tray.

When you get to torquing the heads on a roundcase, you're going to find that you can't get a socket on there. A crow's foot might work, or you can make up one of these. Keep in mind that when you use this, it will change the torque arm on the wrench so you have to compensate for that. Rather than try to explain it, I'll repost a note sent to the bevelhead's list a while back. Author is Luca Guala.

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Heads,

I have encountered five different methods to torque a hidden bolt such as those on a Ducati twin's heads. All these methods work and all have their church and adepts who will swear for one and curse the others.

Method one to three require that you make yourself an extension spanner by welding an appropriate socket along the handle of a flat "star" spanner at a sufficient distance to clear the obstruction above the bolt/nut. You can also buy the appropriate Ducati tool: saves you time, lightens your wallet.

Method one, for the mathematically inclined: fit the dyno wrench aligned with the extension spanner, try to assess the centre of application of the force of your hand (which falls roughly under your middle finger, my dyno wrench has an arrow that marks this rather approximate point, by gentle concession of USAG toolmakers), measure the length of the extension and apply the following formula:

Dyno wrench torque setting = Torque required at the nut X length of dyno wrench arm / total length of dyno wrench arm + extension spanner

Method two, for the mathematically impaired: fit the dyno wrench at right angle with the extension. Now the real torque arm will be the hypotenuse of a right triangle. If the extension is much smaller than the dyno wrench arm, the difference with the "ideal" torque arm will be negligible so no calculation will be needed to obtain a reasonable approximation of the correct torque. the length of the torque arm of my dyno wrench is about 6 times the lenght of extension that I made myself. In this case the error would be around 8% in excess. A variation of this method is to fit the dyno wrench at a slightly acute angle, so as to approximate an isosceles triangle in which the distance between your hand and the bolt is the same as the length of the dyno wrench arm.

Method three: fit an universal joint extension between the extension spanner and the dyno wrench. this way you cannot tighten the bolt unless you push on the head of the dyno wrench (the opposite side from the handle) with the precise force needed to keep the universal joint upright. This force will produce a torque on the bolt exactly identical and opposite to the excess torque generated by the extension. You must take care not to grab the dyno wrench but just push on it. It works. It's not magic. It's mechanics. No calculations required.

Method four: buy the "C" shaped new Ducati tool or have one made and forget about the above.

Method five: repeat the mantra "the important thing is that all nuts be equally tightened" and tighten them with a normal spanner and all your sensibility.

I repeat: all methods work

ciao

Luca