need to order sprockets for k1 1972 st70 with st50 engine

i have a k1 st70 on a st50 engine, what's the sprocket tooth size front and back for this engine, and also is it 17mm shaft size? before you ask, it came with no sprockets or chain, no retainers or rear sprocket spacer. hence why i am trying to find these now. (EDIT: I found the rear sprocket, it has 42 teeth).

i was thinking of going 15t at the front, just want to keep them standard, how many chain links would i need to have on the chain and how many teeth at the back?

FRONT SPROCKET: i was looking at a 15t one of these with 17mm shaft size:

http://www.ooracing.com/store/index.php ... oductId=13

FRONT SPROCKET RETAINING KIT:

http://www.ooracing.com/store/index.php ... roductId=4
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would i need a REAR SPROCKET SPACER, if so would this do:
6mm bolts fits the Honda type range and 17mm spline

http://www.ooracing.com/store/index.php ... uctId=1769

also, can anyone find a chain for me that would do the job, what pitch would i need for the chain and how many links for the average sprocket 15t front Xt rear combination? (X being the unknown quantity for rear sprocket teeth, if you have a 15t front sprocket, could you count the number of rear teeth and chain links for me? thanks.
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i just want standard but there's ratios here for increasing top speed/acceleration/power etc with front and rear sprocket teeth combinations:

http://www.ooracing.com/store/index.php ... oductId=18

here's a picture, how is the front and rear sprocket held on, will look for parts diagrams in the meantime:

The original ratio was mostly 15-38 on a standard ST50 dax.
However, it could range from 13-15 / 35-42.

Nearly all chains will have to be shortened to the correct length. DID, Iris,... have good chains for our bikes.

You don't need to offset the sprockets.
The other parts look good.

cheers for that waynus. will get the standard ratio you describe. out of interest, does that standard ratio differ for a st70 engine or is it the same as the st50?