kz650 starter clutch solution - ZR7S part

Hi!
New to forum and question related to starter clutch substitution for a 1979KZ650D2SR. Do I also need to replace the starter clutch shaft if I was going to use the better designed ZR 7S starter clutch assembly or can I use the original shaft from my KZ 650 and just add the other parts?

Sorry if this is a redundant question for you but before I start the parts search i wanted to be sure.

Thanks in advance!

Wishing I would a run across this back when I re did mine(4 years ago I think) ....... the older design parts are working fine (replaced all) and should out last me but better is always .....well better.......... o yah and wish I would a layed mine on its side too........ read you could but ti sounded scary to me but after seeing it I could a saved myself a lot of extra work...... even though it was nice to have the motor on the work table again.

When I did mine I pulled the front of the bike up using a strap around the frame gusset behind the head stock hung from a beam in my garage ceiling. I got the front up to about 45degrees before the gauges started interfering with the strap. I also took the front wheel off. This provided very easy access underneath and to both sides of the bike. Worked great.

I don't believe I did. Check how the oil pump gears mesh with the starter clutch shaft, also check the overall length.
I'm hesitant to play expert without the parts in front of me so perhaps somebody else could chime in.

I just did the mod on my 650 hybrid, lucky to get a complete ZR 7 gearbox form Europe. Just got all back together and the starter clutch won’t disengage, so it’s jamming I suppose. I made sure I had the spacers in the right spot, the 2mm in the clutch. I would like to brain storm what it could be befor going through the hassle of stripping down again

Without seeing it first hand, I can’t really assume to know what is wrong.
All I can do is post the correct shim thicknesses and in which order they are installed since you only said you put the 2mm one in the “right spot”.

These are the right spots:


If this is exactly how you installed everything, then I am at a loss to explain why it has seized.
Maybe a bit of grit has fouled the operation of the clutch??
If it was me, I would take it all out and solvent wash the sprag mechanism and all the roller bearings, re oil and reinstall.

Thanks for your thoughts Draftrusty. I think I'll take out the starter motor and see if I can free it up through the idler gear. I definitely have 2 x 3.2mm spacers left over from the swap. Even if I was to get the position of the 2mm and 3.2mm back to front, it should only miss aline the gear to Idler gear

This fix on my stater clutch has opened up a can of worms, I’m guessing the first time you installed your’s Daftrusty, you had it right to the parts lists and drawings online.
I swapped the spacers with the 2mm outside and the 3.2mm inside the coupling and found the starter gear runs freely.
I compared the measure from clutch gear to the starter gear on the old and the new and their now the same

[attachment=128092]EA853EF9-636D-4DC7-A4BB-1638E01A4621.jpeg

Would a 90's ZR550 starter clutch be a suitable option? Seems to be nearly identical parts list

BlackEyeCafe wrote: Would a 90's ZR550 starter clutch be a suitable option? Seems to be nearly identical parts list

No. The zr550 uses the exact same 3-roller style clutch as the 650/750 but they are a different size and not compatible.

Hi All, sorry if this is a stupid question or has been asked elsewhere.  Will this solution work on a GPz750 (ZX750A) as well as the z650?

Cheers, my starter clutch is gone and I want to get it running this summer.

ZX750A wrote:

Hi All, sorry if this is a stupid question or has been asked elsewhere.  Will this solution work on a GPz750 (ZX750A) as well as the z650?

Cheers, my starter clutch is gone and I want to get it running this summer.

Yes. Both the 650 and 750’s share the exact same secondary shafts and 3 roller starter clutch. So the zr-7 starter clutch upgrade can be done to both in exactly the same way.