green river rc,

Many attribute "blow down" timing, the difference between intake and exhaust timing in the cylinder as the major factor in a 4-2 break. The best explanation I've found is in Bob Hunt's "Stunt Flyer Video Magazine". Vol1, No1 has an explanation by Dean Pappas (including a paper to be made into a timing wheel). He shows how to check YOUR engine timing. In Vol1, No3 he shows how to modify an engine for the correct blow down. The videos (or DVDs) can be ordered from Bob Hunt.

Caution: If you make a mistake, you will probably ruin your cylinder.

You might try adjusting head shims before drastic measures, though.


George