holed piston/seizure

[camel]

now i know the obvious but im a bit stuck on this one
engine spec
r.s stage 4 200
rs clubman
std delly 22 with a 118 main jet and std airbox
timing at 18 degrees
my friends bike has holed a piston once
ive rebuilt it with a new piston profiled to ralphs orig spec,now after doing quit a few miles he,s nipped it up,its running but lost power so ive had the top end off and its got the usual signs,but its starting to hole the piston again,i did suggest going to an indian main jet of 123...but he said it ran very lumpy with this fitted
im going to rebuild the bike again but obviously without adjustments its going to happen again
i hate std carbs.....any suggestions on wot to adjust

[alcoholic maniacs sc]

i ran the same set up and found that i needed to take out the airfilter but leave the box. (dont forget to put a little oil in the bottom of the air box to catch dust/s**t) a 122 main jet, before all this lean running mugello nonsense you went up on jetting as high as poss and put a fast flow fuel tap on the tank or it will be starved on the motorway if you crack on a bit. a 118 is too low im sure but you may also have a leaking head gasket??!1 if its a little warped the tiny amount of air bleeding in will do this. rub it down on glass with 1500 grade til youre sure its flat and fit a thicker head gasket if you have only a thin one on for safety.

[camel]

ok thanx for the reply...suppose it stands to reason with the 122 main..more fuel more air...shall give it a whirl

[rog60]

Hi I'm running a very similar set up. Using a Camlam 'fast flow' washable filter through airbox with 123 main and 48 idle and an AF standard inlet manifold which they've reamed out to 26mm.
Hope that may be of some use to you.