Engine Swaps

Which engines will fit the 1978 KZ650 frame, and are there any surprises lurking if I choose a non 650 engine? Thanks

I am pretty sure a KZ700/750 is basically a drop in swap. Anything else will require fabrication. Motor mounts, chain alignment and exhaust port location will be some of the biggest things to consider. An 810 piston kit would be less work, though I seem to recall a member here shoehorning a 900 engine into a 650 frame. Seems like he had to remove the engine to do a valve adjustment.

Hasn't Bevelhead got a 1170 GPZ motor in a 650 frame 

All 650/700/750 aircooled fours up to the ZR750 zephyr are based on the 650 motor and are pretty much a physical drop in swap.
The later front rubber mounted engines will need a small amount of work for the front mountings. 
Ignition and charging systems differ on later models so that will need addressing.
The larger 900-1100 engines are a common swap but are a tight fit with engine removal required for valve adjustment etc.
The 998 /1089 J type motors are shorter than the earlier 903/1015 kickstart ones and an easier fit .
Suzuki GSXR/BANDIT /RF oil cooled motors are also a popular mod and again the smaller 600/750 engine are an easier fit then the taller 1100's.
Apart from the Z650/700/750 swap all the others require entirely different mounts but with the right skill and tools anything can be made to fit anything else.

 

wrote:

Hasn't Bevelhead got a 1170 GPZ motor in a 650 frame 

That is probably what I am remembering.

Baldy110 did a big motor conversion  
 Bike was red with white trim
Dave

Sadly he is offline since June 2020.

kzrider.com/component/joomgallery/kz-100...-clone1-6811#joomimg
kzrider.com/component/joomgallery/kz-650/78-kz650c-212#joomimg

wrote:

Sadly he is offline since June 2020.

kzrider.com/component/joomgallery/kz-100...-clone1-6811#joomimg
kzrider.com/component/joomgallery/kz-650/78-kz650c-212#joomimg


Good catch     I didnt remember the ELR clone    , I always think of Baldy and the red  bike
 

The rubber mounted KZ750 and GPZ750 motors require a spacer at every motor mounting point on the engine cases (8 places) The sprocket will line up perfectly (have a 82 Spectre motor in my 78 KZ650) No frame mods necessary even for hopped up versions. You will need a electronic tach as the later engines do not use cable drives.

The earlier KZ900/1000 motors are harder to fit than the later J/GPZ1100 motors, the later motors seem to be swapped more (just finished a KZ650 frame for a 78 KZ1000 motor)
The frame needs all 3 front motor mounts removed and replaced. Not sure if the frame needs extra bracing but it could not hurt, KZ650 has a nice stiff frame. If you set the motor cases right on the bottom frame rails you can take the cam cover off to adjust shims. Mine ended up having 3mm of clearance to the frame rails but I did grind off some material on the center motor mount castings to gain a bit of space, those center mounts are not used (I think this was the factor that caused cam cover clearance issues in previous swaps)

I am putting a 1197cc street kit in my motor with VM33 smooth bores, big valve KZ head and .418" cams. Not intending to flog it so hopefully the KZ650 frame will be rigid enough for 110-120 HP. They used the KZ650 frame as a test mule for the GPZ750 Turbo engine when they were developing it (110 HP)

Its much easier to go for the GPZ750 swap, with a big bore kit/cams/carbs/pipe you could be making about 90-95 HP and about 40lbs lighter than a 900/1000 swap that has only 15 HP more. The only reason I did one was because I wanted the extra big crank torque the larger engines possess.