ZR7 Motor in a KZ750

Hi all, I’m just about to install a ZR7 motor into a 1980 KZ750E frame, I know it’s something that’s been done before so can’t see any issues. The original KZ front top motor mounts will work but the ZR7 motor was originally rubber mounted, will this make a big difference with vibration if its solid mounted or would I be better cutting off the KZ mounts off the frame and fabricating something up to take the ZR7 rubber mounts?

Sorry for this bit of a late response.

I did the same thing only a bit different. I put a '82 750 Spectre motor (originally rubber mounted) in a KZ650 frame. You end up having to make up the rubber mounting space with aluminum spacers. This has to happen at every engine mount face. The spacers I made are 6061 aluminum, faced to length on a lathe then drilled for the engine mount bolts.

The key is bolting up the motor using all the motor mount plates to suspend it and carefully measuring for the missing spacers. The lower rear frame mount tab under the sprocket needs to be maintained tight to be sure the chain lines up.

There is no difference in ride from a normal rigid mounted KZ.

The original Kawasaki rubber mounting system is a bit complex to try and retrofit onto a solid mounted frame - Way too much work involved.


 

As Injected noted, there is little discernible difference in ride quality  between the solid engine mounts and the rubber ones. Weird I know…
The Zr-7 motors do not have the lower engine mount bosses. Not on the frame nor on the motor. But they did add a horizontal brace between the frame hoops at the lower location. If possible, you may want to fabricate a brace you can bolt into you existing lower engine mounts to help regain the frame rigidity that will be lost. 
Also, just out of curiosity, how are you dealing with the different ignition pulse/crank trigger setup that the zr-7 uses? Are you wiring in the zr-7 ignition module into your kz harness or are you machining a new reluctor?  I’m just curious how folks go about making that part of the swap work. 

Thanks for the replies, I ended up cutting the old KZ mounts off and fabricated some new ones which allowed me to use the ZR7 rubber mounts. looked factory and worked great, unfortunately no pictures as it was a customer’s bike

wrote:

As Injected noted, there is little discernible difference in ride quality  between the solid engine mounts and the rubber ones. Weird I know…
The Zr-7 motors do not have the lower engine mount bosses. Not on the frame nor on the motor. But they did add a horizontal brace between the frame hoops at the lower location. If possible, you may want to fabricate a brace you can bolt into you existing lower engine mounts to help regain the frame rigidity that will be lost. 
Also, just out of curiosity, how are you dealing with the different ignition pulse/crank trigger setup that the zr-7 uses? Are you wiring in the zr-7 ignition module into your kz harness or are you machining a new reluctor?  I’m just curious how folks go about making that part of the swap work. 


 

I put 2 extra tubes in the frame, one at the bottom and one higher up for the oil cooler to mount to. The full wiring loom from the ZR7 was used