[0U812]

 Ok   I' looking to use a 1956, 500cc singal frame, and bolt in a 1956 twin 700+?? cc moter. into the frame.  Problem is the frame with the 700cc+ is in has been modfied.... and I would like to use a front forks more like when it was made.  I do not want to modify the 500cc single ftame.  Will the 700cc+  moter swap in into a 500cc frame??

[DNash]

It should pretty much drop in. You may need to use the head steady for the twin (they had a significantly beefier head steady, I think), but I'm pretty sure the base frame itself is pretty similar between the Bullets (350cc or 500cc single), 500 Twins, and Meteors (700cc twin) of 1956. I think some of the later twins also had a big alloy casting that bolted to the gearbox and the frame to make the whole affair more solid, and I gather that's a pretty desirable (albeit hard-to-find) part for those frames.