differences between 81 kz1000m1 and kz1000j1?

just wondering what the differences between the 81 m1 and 81 j1 are? from my searches, the only differences between the two happen to be all appearance related. am i right in assuming this? the engine case p/n, tank p/n, and frame p/n all match for the most part. this would help me in parts searches. i'm really thinking about going with some j1 wheels to get away from tubes and rear sets. and since i switched the bars from stock to clubmans, i had to get creative with the clutch cable routing and need to get a shorter cable, and by the looks of it, the j1 bars are shorter and so would the cable too.

It's not uncommon to modify the 1000 csr or ltd. below are a couple of recent topics. there was another one a few year back in which a gpz conversion was done, but I don't recall whose bike it was.

CSR1000 Project Build

1981 KZ1000 J-to-K build

well it won't be a total refit/conversion. it's been running great aside from the 94 kz police exhaust that i put on it. the left muffler broke off right at the left collector/muffler joining weld on a rather nice ride that ended sooner than i wanted it to cause of that. but here it is shortly after i finished painting it this spring, before the muffler broke off. my interest is mostly in the motor side, for parts like clutch cables since the original is too damn long, and i don't like how creative i had to get with the routing of the clutch cable to have no sharp bends. right now i just want a shorter cable that will interface with the clutch actuator rod on the m1/j1 motor

The 1000J is the sport version of the later 1000's (behind the 1000R or ELR bikes) they have hotter cams and make 10-15 more hp than the other standard versions. Yes, the bars for the J model are low (really low in fact) but fit the overall feel of the bike.

If you run into an actual 1000J don't strip it for parts, part it out or chop it up; there were only 5000 or so made in 81, and something like 10,000 total (If i remember correctly) they should go up in value

i wouldn't dream of stripping it down or turning it into a ratchopbobratcafracer. like i said, i'm more interested in the parts interchange so i can get properly sized stuff. i'm considering getting a second seat pan to do more of a j style tail on my m1, by shortening the seat foam and attaching the tail fairing to the pan itself, so if i want to convert back it's as easy as 2 pins!

If you do a second pan to fit a J tail it's going to probably be a custom piece; the 1000J has two tabs in the front and the latch mechanism in the rear. They are also near impossible to find.

When I had my J model I had to modify an early kz1000 pan to fit, the fromt portion almost fit, and the back had to be made. That decision was made after I posted a wanted ad, browsed eBay and found three different un-answered want ads on here.

The way i'm thinking of modding the seat is the tail piece would actually get attached to the pan and not the frame, and probably have a small storage compartment inside the extra space. This way, if i wanted to go back to the original m seat, it's just 2 pins. I may also use a 70's tail piece too