80-81 1196 Big Bore piston kit

[ViperRon]

Questions 1196cc big bore kit

First who has done the kit and hows things going?



Second I know several of you can answer but I need to know for sure if the clymer manual is correct on the piston side clearance being 0.0016-0.0018 Just me thinking but with this being aircooled I'd expect more like 0.004 as 0.0016 is very tight. I have a machine shop ready to do a cylinder set I got that was a good candidate as it had bad wear, looks like rings broke.

My measurements from the 1196 overbore pstons are 2.9331in which translate to 74.5 mm. Add to it 0.0016 and 2.9347 is what I come up with as bore for cylinders. Need you guys to verify this as I do not want to seize a set of pistons. I will still have to clay the head make sure of valve clearance.

I do plan on folowing a break in procedure when its all done.

[CaptonZap]

I can't give you an answer, but I have a thought to ponder.
All aluminum is not the same. Different alloys have different rates of expansion. The factory used a certain alloy with a certain rate of expansion and sized it to fit the application. If you know for certain that the replacement pistons are made of the same alloy as the OEM, then the OEM clearance would be a safe bet. Usually the piston manufacturer will tell you what clearance to run. Lacking that information, my rule of thumb has been .001 per inch of diameter of the bore. YMMV (Your measurement may vary)

CZ

[TomB]

I bored old Triumph engines with 2 thou piston/bore clearance with cast iron jugs, never had any problems.

I would think 0.0016 - 0.0016 sounds right for a more modern engine. The XS1100 bore wear limit is 0.004 so be careful you don't bore it that big its worn out before you start.

And you should always take your pistons along to a machine shop who are doing the boring work for them to bore the jugs to.

[trbig]

I can't vouch for this kit, but I know the Wiseco pistons had a .002 clearance. This was from the 1179 pistons, but the 1196 pistons were the same.