Requesting Engine Rebuild Advice Please

Hi.

A while back I got hold of a free parts bike to go along with my 1980 KZ750 LTD.
It's a KZ750 E, of indeterminate provenance, but it was cheap at the price and the odo read a scant 8,000 miles.

The motor on my regular old daily is oldish - at least 45,000 miles - and not necessarily well looked after. Basically every gasket possible leaks, it won't stay in second gear and has developed an orchestra of odd sounds. I plan to keep riding it until it stops, but in the meantime I want to get this other motor into a condition to just pop into the bike and go.

I took the first step in seeing what was wrong with the donor motor yesterday, and now I'd like to ask the wise folks here for advice and opinion.

Inspecting the outside, there was some weird grainy oily gunk in #1 intake runner
Upon removal of the cam cover, everything looked pretty good with almost no wear marks and a nice tight camchain. everything turned clockwise freely using the 17mm nut at the points end of the crank

The head came off easily to reveal more gunk in the #1 combustion chamber.

I removed the jugs too, to have a look at the pistons and further in...
The iron sleeves inside the jugs are loose, and come out freely by hand - is this normal? photos attached.





to discover that the rings on #1 piston appear to have seized in a compressed state inside the piston - photo attached.







My assumption is that this caused the bike to be retired - it wouldn't work properly if the rings aren't sealing at all right?

So at this point to get the motor back together it needs the obvious like gaskets and o-rings. It will also need new rings - a new set for each piston seems wise, if expensive. Is it unwise to re-use the piston with new rings? if i need to get new pistons, then should i get the big bore kit and go crazy?

Is it a dumb idea to disassemble the motor further? I'm not afraid of the work, but I always prefer to do as little as possible, including spend money.

any thoughts about what else i ought to do?

thanks

I don't have tons of experience with KZ engines but I'd say the liners pulling out like that is not normal. Very strange. They are normally installed with a light press fit. As for the rings, it's not unusual for the rings to stick on a bike that has sat for a decade or two. Soaking the piston, up side down, in something like Berrymans carb dip will soften any carbon and/varnish which is holding the rings. Most likely the pistons can be salvaged...assuming the cylinder block is okay. Hopefully someone here will chime in with more advice in that regard.

If reusing the pistons always use a ring groove cleaner, Loose jugs is weird. Wonder if there was a serious overheat. Then again it may not be a big deal. they're not going anywhere with the head on.

Have seen sleeves loose like that on a number of bikes over the years. They will work , but a tight press fit is better for proper heat transfer to aluminum casting . Its worked this long so dont over think it.
Clean every thing to like new condition .
I would install all new rings and do a light hone to the cylinders and call it good.
New pistons and overbore are nice but not needed.
Dave

Pics of the bores? I've seen them loose like that. Shouldn't be a problem.
Steve

Loose sleeves is a common "problem" on the old ZEDs .but not a reason to re-use. the cylinder.
If the bores have an undamaged surface.., a light hone and a set of new piston rings are necessary for a good compression.
Clean the combustion cambers, lapping the valve seats an valves.
A set of new viton valve stem seals is the best you can buy for a longer riding fun.
Use plastic tubes to prevent damaging the sealing lip during the installation by the valve stem key groove

hey thanks a bunch to everyone who chimed in here. If it all works out, I should end up with new(ish) motor for a pretty low cost. That's great news in these uncertain economic times.

loose sleeves should be reset what i do is push sleeves out bead blast inside of cylinder block then blast out side of sleeves heat cylinder block and press sleeves back in, I would not put it back together with sleeves loose!