550, 650, 750 share a bottom end?

I'm thinking one of these is a factory big bore. Example: maybe the 750 has a 650 bottom end and bigger cylinders? Or the 650 is a 550 bottom end with bigger cylinders?

I'm curious which has the best power/weight ratio.

or (shudder) perhaps the 550 and 650 have the same bottom end as a 750 but smaller cyls?

550 is different. The 650 and 750 are similar, All three do share some case covers though.

None of the above, sorta, kinda :laugh:

550 is not related to the 650 or 750, so you can ignore it.

76-81 KZ650 is almost like the 80-83 750, except the 750 does not have a kick starter and does have HyVo style cam chain instead of the roller cam chain of the 76-81 650's.

82 and newer 650's are identical to 80-83 KZ750's with the exception of smaller bore, cams, and I think carbs. GPz750 is a little more complicated, and the 750 Turbo is in a class of it's own.

80-83 KZ750 cylinder block and head will work on all 650's, but you have to use the cam sprockets and sliders off the 650 on the 76-81 650's.

I believe that all the KZ's use the same transmission cover. I know 550/650/750/750 twin all use the same cover, and I think the others do also.

So it sounds like the 650 and 750 engines are about the same size and weight, yes? Then the entire 550 engine is a little smaller and lighter than the other 2. correct?

Yes, for the most part, the 650 and 750-fours are interchangeable and are basically the same size (but I'm not sure how much weight difference there is, if any). As the years get farther apart, and the gpz line comes into play, the motor mounts will have some variations (some converted to rubber-dampened, some added or deleted (I think)), but the lumps are basically still interchangeable with very minor changes.

Also, there is a tariff bike. The 700 is basically the same as the 750 but was only made a couple years to pass under a displacement limit for tariffs.

Yes, the 550 is significantly smaller, even though it shares the ignition cover, trans cover, and breather cover, along with some transmission parts compatibility. A 650/700/750 motor will not just bolt into the 550 frame without cutting and welding. The 750 frame is bigger, but probably only a little heavier than the 550.

Now that I think about it, I wonder if it's paossible to change out the 6-speed trans on the 550 and put in a 5-speed trans from a 650 with the kicker. It would be the only 550 ever to have a kick.

I have a 550 and a 750 engine, both currently out of frames, in my garage. If I can find a way to weigh them, without breaking my back, I will post the difference.

.

What's all the fuzz with the Hy-vo chain lately ?

I mean why getting a hy-vo chain for the cams instead than a roller ones ?

regards,
laurent

It's not a case of swapping out a roller chain for the HyVo style (link plate chain), it's a case of HyVo being stock on 750 fours and 82 and up 650's.

That's what the "fuzz" is.

thanks all. That makes me wanna buy a 750!

and just FYI - I've owned a 550 and 750 many yrs ago. I currently have a 1000 and a ZR-7S (modern KZ750).

I'm trying to pick a bike for a project I have in mind and I think the kz750 has the power to weight(size) ratio I'm looking for. thanks for the info.