uncles sams 700 vs 750

hey guy , so i came up on a free 84 KZ700A engine that i will be using at a donor for my current kz750E. My plan is to fully build the kz700 (as a 810cc) that way my bike wont be out of commission for any real period of time . im looking for any major differences between the 84 kz700 and 81 kz750E beside the cylinder bores and cylinder head? and can the kz700 be bored to fit 810 big bore kit or is it recommended to start with the 750 jugs? i will be replacing the cylinder head with the a 750 head for obvious reason.

my goals for the build is to starting with the bottom end is:
~ to do a 6 speed trans mission swap as DaftRusty did complete with zr7 secondary shaft,starter clutch, oil pump, with oil pan and cooler.
~ i will be running an 810cc big bore kit
~kz750 head with milled .010" with mild port , built with new guides and valves
~83-85 GPZ cams that have a .5mm more lift and slotted cam gears

i would appreciate any other information regarding the differences between the two engines or any foreseeable problems i may run into.

thanks guys.

~Eric

The 700 engine case is set up for rubber mounted engine mounts. I bought a set of the mounts with thoughts of converting those on my 750 but never did the mod out of laziness. PM me if you want to acquire a set of mounts for cheap.

I don't know if the 700 cylinder liners can be bored to 69mm.

ya i received almost a full bike. unfortunately most the parts where in buckets and the buckets were filled with water. so i pull the engine and scrapped just about everything else. the motor mounts are the only other thing i kept haha, i thought they looked like great mounts, unfortunately it looks like only the right one will work. my frame is from a kz750h and the left side of the frame has a weldment.

Anyone else know any major differences with these two engines?

Bore is different. 700 has higher compression. Check part numbers if you want to see what's the same and what's different.
www.partzilla.com/

I learned. 810 is max for 750 when its comes to working for long time....

So if the linners thinkness is the same on 750 and 700, will guess the linners will be to thinn...?

But if the whole for the liners is the same, then you have higher margin to borr out?

Hi Kidd. I’ve done the 810 kit in a 700 with a GPZ intake cam. I have about 5k miles on it and it seems to work well. I didn’t measure the sleeve thickness so I can’t speak to whether or not the 700 just has more material in the sleeve than the 750 or if it is smaller all around.

The 6 speed trans swap is a really cool mod. I’m wanting to do the same and have been collecting parts but just haven’t torn the bottom end apart to do it.

ya i two have been collecting parts hoping to do the full build at once. good to know you are running 810 in your 700. are your still running a 700 cylinder head? and is there a reason you are only running a gpz intake cam instead of both?

Its been a while since I've been on.

I'm still running the 700 head. Used a dermal to clean up the casting marks in the ports a little but no real porting done.

From what I've read, GPZ cams shift the power band higher in the rev range. I typically just ride around town and don't really run high RPM, which is where I'd notice the difference with the GPZ cams. I set the bike up more for torque rather than high hp which is the reasoning behind the 810 high compression kit. I can't find the links but I'v heard it discussed that adding just the intake cam will provide a little bump in the mid range while the stock exhaust cam would help keep exhaust velocity high. Not sure there is a any data to back that up but its been pondered in a few conversations. Figured it wouldn't hurt to test it out. Also the cams I found were in fair condition and one of the exhaust cam lobes were questionable. Rather than wait to get it reground or resurfaced, I just used the intake.

When I had the cylinders bored, the machinist didn't bevel the bottom of the sleeves and it was a pain to get the head down over the pistons. I'm afraid I damaged a ring when installing it. He was worried wall thickness and cracking. I've since had the cylinder off a couple times for other reasons and it appears to be fine. About replace them and have the cylinders resurfaced as it appears the ring gaps have aligned in one of the cylinders and a raised area in the gap has formed