can anyone tell me how much clearance is needed between the pistons and cyclinder
 

need to know on a 1979 shovel bored .040 over

depends on the piston cast .0015 if ya cant break it in without hot rodding it .002 to .0025 --- forged depends on the type of aluminum and the cylinder .004 to .010

- http://www.dansmc.com/pistons.htm -- check that pic of the piston -- the wrong jet will fry a piston or 2 also ..

Edit

Check the S&S web tech site they have good down loads for this stuff

http://www.sscycle.com/instructions/...t.php?x_cat=12

TB S&S is a good place for info.. thing is he never stated what .40 o/s pistons he has -- 99% of all cast air cooled is .0015 -- lots of these guys bolt the stuff on an run the hell out of the bike-- stick the piston and come back screaming that someone told them this info -- i just wanted this person to SEE that piston --- and as you know it depends on the material the cylinder is made of and the piston as to what clearance is set to ..

I know , most generic shovel pistons are import anymore unless you drop the big bucks and have a decent shop do it right on the boring , unless I specify and supply the torque plates most places knock them out at .0035+ " on the cast ones .

Between you and me I spend probably 3-4 hours talking to a perspective owner and let them hang around a bit so I can get a feel for how they will handle a new engine and I'll build accordingly . Guy is particular & neat takes of business I'll set it up tight , the guy you know is gonna get 10 miles on it then light it up that motor is gonna be on the loose side out the door .

Dealt with too many not to know better .:D

kinda like when this happens --- buzzing on the interstate (I-10) and all i heard was the sound of pieces of metal going in every direction -- had the samething happen one night in 1970 on the way home from the french quarter -- had an old 39 knuck with 90 o/s jugs -- B0O0OM that one broke the rod off at the top of the flywheel and still ran on the front cylinder - enough to get me off the I-10 and coat everything with 70 wt oil..