1983 kz750n compatibility

I have a 1983 kz750 n Spectre. What are the differences between my motor and a kz550 thats also a shaft drive? Is the only difference the bore size? Or would a kz550 motor be totally useless to me for spare parts?

I think the 550 engine is probably completely different, with the engine itself being smaller (and not simply having a smaller cylinder bore & pistons).

The drive shaft stuff may swap. In the diagrams depending upon which 550/750 models you compare, the 550 & 750 have the same final gear assy & some of the other stuff is the same. The part numbers may be different depending upon whether or not the part is silver, but they are probably interchangeable. The Spectres are black, whereas the Ltds are silver (the 84 550-F2 is listed as an Ltd in the diagrams, but it is a Spectre).

There may be the odd item that interchanges but for the most part, the motors are very very different.

Thanks so much for your expertise. Would any KZ 750 4 cyl motor be compatible with mine? or a 650 or only the 3 year span that they made the kz750n?

Here are the 700/750 shaft drive models (USA) --- the engines are probably a direct swap.
82-83 KZ750-N1/N2 Spectre
83 KZ750-F1 Ltd Shaft
84-85 ZN700-A1/A2 Ltd Shaft

Note: in Canada there may have been an additional shaft drive model (not sure) & the ZN was probably a ZN750. Europe got the GT750 Shaft drive models but I don't know anything about those.

The chain drive models have a different output shaft. I don't know much about it. I'd guess you'd have to swap out the transmissions or convert your Spectre to a chain drive... just a guess. I have no idea how much work either option would be, but I kinda recall someone doing the conversion to chain drive (???)... my memory could be off though. :blush:

Thanks so much for the info. Where would be a good place to pick one of these up. Mine isn't running bad it just has a primary chain that has stretched a little and makes a little noise. I would like to find another motor and rebuild it this winter. Again I appreciate the info.

FritoVL wrote: Thanks so much for the info. Where would be a good place to pick one of these up. Mine isn't running bad it just has a primary chain that has stretched a little and makes a little noise. I would like to find another motor and rebuild it this winter. Again I appreciate the info.

A primary chain that's stretched a little and makes a little noise?
You mean like at least 90% of the KZ650s and KZ750s still running?

Syncing the carbs usually makes the noise go away.

Could the noise be the cam chain? If the bike has an automatic adjuster, you might want to service it or replace it w a manual unit. I installed a Krieger but I think I would have preferred Ape Racing's. They both work the same but are slightly different from each other.

Servicing the existing tensioner is very straight forward, and a lot cheaper than replacing it with a manual unit.

With a manual tensioner there is no ambiguity. With the automatic type you don't really know how much slack has been taken up. There is the possibility that the auto unit can retract under certain conditions, causing bent valves or severe engine damage (from the Ape Racing site).

1981 KZ650. The valve clearance check section of the manual doesn't mention the tensioner. In the tensioner section it says to remove it whenever anything is done that slackens the cam chain such as removing the valve cover. But in the camshaft installation section it says to install the tensioner before turning the crankshaft. Kinda confusing for a first timer.

Sorry, Martin, we will have to agree to disagree. APE sells a manual tensioner, therefore it only make sense that they print marketing hype about it being superior. Consider the sheer numbers of bikes with automatic tensioners, versus the small number with manual ones. Maintain the automatic one properly, and you will never have an issue.

Thanks. You're probably correct. I was thinking that the warning is more for the Big Kaws, especially if it's been over-bored or a guy goes to the drag strip. In my case it had more do w the service manual which was kinda confusing. :blush: