engine seized up help kz750

Not sure where you live, jammor, but there's a guy selling a '77 750 twin engine for cheap in the Atlanta area.

atlanta.craigslist.org/mcy/1035288145.html

yes i agree at a minimum he should have mic'd the pistons and rings after he honed the cylinders to see if they fit properly. In his defense he never saw the whole engine as i just took him the cylinders to be honed...the only testing i did on the bottom end was to pull on the rods to see if there was any play. And there was no noticible play and the engine rotated freely. i would really like to disassemble this engine now that i have it down to the crankcase only but the rods are frozen tot he crank. do you think if i pull a side cover i can get to the rod nuts? I have split rod ends (not roller bearings)

yeah im gonna go look at it today- the one from craigs list

ok i bought the 77 kz 750 engine. The vlaves are rusted open. I see water in the engine case- I bought the whole engine for 75 bucks so i plan to tear it apart and see if any of it is still usable. the crank does turn! maybe i can make one good engine out of the two i have. Ill end this thread now and start another once i get into the new engine. Thanks for everyone's help
jim

Jim, When rods weld themselves to crank, the crank & rods are usually toast. "tis an excellent opportunity for education" since engine must come out any way, why not blow it apart and get familiar. at least you'll be able to classify spares. and in the event you do score a cheep eng/wrecker you have the opt of doing a fairly fresh rebuild for the cost of gaskets,seals & bearings using donor parts from "scab", If you go there pay close attention to oil pump and passages. useing stock cases elimiates the need to re-register/title etc.and may reveal shortcomings w/"new eng" before they become issues. luck G

Hi gane
thanks for the advice. i will completely tear the old engine down. I would like to see what seized, whcih journal, etc on the crank. Id like to compare that to my new bottom end (I bought a used 77 kz 750 engine today but judging by the condition of the top end-ruster- i am scared to death that this used engine bottom end is completly rusted- escept for the fact that then engine turns over.
so anyway---i have never disassembled one of these engines and taking apart my shot engine will be great experience. By chance I met another motorcylce mechanic tonight and he looked at the new (used0 engine and advised me not to take it apart but drain the oil, clean it as best i could, feel for play on the rods and just bolt my new top end on it.
I appreciate his advice but this engine has sat for !@ years and i see water in the crankcase. I want to make sure my engine is good from top to bottom so i will see how much effort it takes to disassemble the old engine and if not too much i would rather do what your are recommending (i think) and build it from the crank bearings up. I suppos the 78 has roller bearings and if it does i will not disassemble them. my bike has split bearings.
either way I think once i get into the crankcase i will feel more confident in either taking this task on or posting a great "prject bike" on kzrider.com!

jammor wrote:

Hi gane
thanks for the advice. i will completely tear the old engine down. I would like to see what seized, whcih journal, etc on the crank. Id like to compare that to my new bottom end (I bought a used 77 kz 750 engine today but judging by the condition of the top end-ruster- i am scared to death that this used engine bottom end is completly rusted- escept for the fact that then engine turns over.
so anyway---i have never disassembled one of these engines and taking apart my shot engine will be great experience. By chance I met another motorcylce mechanic tonight and he looked at the new (used0 engine and advised me not to take it apart but drain the oil, clean it as best i could, feel for play on the rods and just bolt my new top end on it.
I appreciate his advice but this engine has sat for !@ years and i see water in the crankcase. I want to make sure my engine is good from top to bottom so i will see how much effort it takes to disassemble the old engine and if not too much i would rather do what your are recommending (i think) and build it from the crank bearings up. I suppos the 78 has roller bearings and if it does i will not disassemble them. my bike has split bearings.
either way I think once i get into the crankcase i will feel more confident in either taking this task on or posting a great "prject bike" on kzrider.com!

I have the factory service manual. The bottom on the 750 twins is pretty complicated, due to the balancer assembly among other things. There are people here who probably could do it in their sleep, but you might want to get an FSM before you try it for the first time. It will alert you to the wierd stuff like having to install a 6mm screw somewhere to hold something in place and what not.

Yeh i have a service manual but it is on disk and I have not looked yet to see how hard this will be. I dont guess I can hurt the seized engine much so i'll practice on that one first