DKW NZ 350

hi guys, does anyone know the piston to cylinder clearance size. need to find out for the machine shop to rebore. also the ring gap when inside the cylinder. thanks in advance, andy

Hi Andy,

I had this question also for a time ago;
Here the answer from Frank;

Its normally the manufacturer of the piston who tells the tolerance between piston and cylinder, depending on the materials and manufacturing methods used.

Those tolerances stated in the DKW wartime workshops manuals are for the original DKW pistons and they are not valid if you use a modern repro piston.

Normally the cylinder is grinded to exact measures, for example 72.50mm, 73.00mm, 73,50mm and the manufacturer of the piston has took care of the tolerance when manufactured the pistons.

Normally the tolerance is stamped on the piston dome, for example 72.85mm, when cylinder then is grinded to 73.00mm, the tolerance is 0.15mm.

//Frank

hi martin
there is no markings on the piston size wise. i suppose i will just have to take it down to the borers and tell them the tolerances of the wartime ones and then see what they say. i have looked up an old post on here and it says that .17 is the clearance but modern pistons it can be .05 according to the guy i got the piston of its a nos izh one made in the 70's so do the wartime tolerances apply ? on the good news front i have sorted out the damaged fins on the cylinder you sold me. i took them to a professional welder to do and guess what ! as soon as i got it back and started to clean it up the repairs broke. so i did the welding myself, put it in the oven at 250 degrees to see if the welds would crack and they didn't. so a self taught welder like myself is better than a qualified welder. quite pleased with myself. cost me 45 pounds tho in his charges. posted a picture on here for you to see the cylinder. cheers, andy

Here the cilinder from Andy.
I let weld several cilinders, never had a crack again.