GPz1100 cylinder block

I am working on an 81 GPz1100 for my friend. He has owned the bike for about 1 year and told me he is noticing a loss in power. I did all the normal checks and found the valves were leaking.
I tore the top end down and while checking the pistons and cylinders I noticed at some point in the bikes past someone had installed an MTC big bore kit, score for my friend. While checking the cylinders I ran my finger down each cylinder I felt a small bump / buldge on the backside of each cylinder. The bumps are about 1 inch from the top on the intake side and are about 1 1 /2 inches wide. Each cylinder has this bump in the same spot, You can't see it but only feel it. It is not a ridge but rather a bump. I have never encountered this and was wondering if anyone else has. There wasn't a ridge on the top of cylinders that would indicate a high milage motor and I can see the cross hatch marks from a honing.

What is the piston / cylinder clearance, is it in spec.

Could the pistons skirt or ring area be rocking or slapping the cylinder wall? maybe a little too much clearance?

Is the bump the high spot with a low spot on either side of the bump? or the other way?

How big was the bore kit?
Maybe sleeves are too thin/junk.

maybe thin sleeves....... :huh: I've seen that when some one installs too big of a kit in stock sleeves....... :ohmy: over bores the sleeves :blink: the block casting will cause high spots from the heat cycles ... (liners too thin) :S ....I remember one where you could see a lot the fins in the sleeves..... :blink: junk

The pistons are 74mm so I believe it is the 1135 cc kit. The bump dip is on the top side, it is smooth coming up the cylinder then drops down toards the top. It very slight. I am going to put it back together and see what happens.
It might be the engine sat to long with the pistons settling in all at the same spot creating the bump from the rings sitting there erroding. When the cylinders were bored they were not bored out enough to take away those spots.