Tee Bee,

When you remove the contra, clean it with soap and water using "Scotch Brite" or equivalent scouring pad. Same for upper cylinder. Be sure to use something non-abrasive so you don't damage the parts.

Many contra pistons are a bit tight...better tight than loose. When you insert the contra, give it a twist in case it or the cylinder is slightly out-of-round. Sometimes there is a tight spot or a loose spot (although there should not be).

Diesel fuel: I think Eric Clutton only sells in Gallons, which is a HUGE amount for a 2cc diesel. Davis or Carlson have it available in quarts. You may also find it on some other online Hobby shops (assuming your LHS does not have it).

You need fuel tubing other than silicone. Diesel fuel causes silicone to swell.

Unless absolutely necessary, I would suggest you use commercial fuel. Mixing your own is great but you are learning to run a diesel. Having doubts about your fuel mix is an unnecessary factor.

George