gpz750 engine rebuild issues

ok so i originally used the blue color code bearings in the engine. the crank was alittle tight but spun. so i ran the engine and let it cool down. and it got to the point where the starter would not turn over the engine. so i stripped the engine back down. i just got in the black color code today and installed them on the engine. i have approximately 1.3 thousandths of clearance on the crank. the connecting rods have approximately 2 thousandths of clearance and the plugs are out of the motor as the top end is still together. i used assembly lube. (that really thick lucas stuff that works great on everyting else.) bolted the case halves together and still really tight. now i know that the max clearance allowed is 4 thousandths on the mains. heres the thing though. the brown size bearing is only approximately 2 ten thousandths thinner than the black. and im having a hard time believing that 1.5 thousandths would make much more difference than 1.3. should i use different lube? also i need to use a rubber oil filter wrench to break the crank free on the rotor and then it gets much easier to spin but not enough to spin by hand.... any ideas on what i should do. its really pissing me off lol.

Are you sure the engine tightness is due to the bearings? Did you pull off the cam chain tensioner cap/spring/wedge before installing the valve cover? Failing to do so will result in over tensioning the cam chain. And what about a ring? Could you have pinched one?

Regarding the bearings I'd use plastigauge or mic all the parts. As long as you have the factory level of clearance you should be fine.

it is definetly the main bearings. everything else was perfect. i actually started thinking that since i replaced the bottom half of the case that maybe it is binding up because of that. so im taking the other engine completely apart to use both original halves. maybe that is the issue everything else is completely in spec. everything has been plasti gauged. that i can think of and mic'd. pluse and looking at the wear patterns from the old bearings im thinking thts it. but i will let you know when i solve it.

MetalMechanic92 wrote: i actually started thinking that since i replaced the bottom half of the case that maybe it is binding up because of that.

Bingo!

The cases are line bored as a set when they are manufactured. I've heard of people mixing and matching case halfs on roller bearing KZ and GS cases, but the plain bearing cases are a different animal. You need perfect roundness.