Modifying a KZ650 rear end

Right now I'm ordering in parts to do a full rear end conversion for my '78 650 (rear wheel assembly, swingarm, brakes, mono shock, rear sets, etc from a '99 Kawi Ninja 900).

I've seen a few 650's and 750's done on here before, and I was just looking for some general tips on what I should expect to run into during the build. How much of an offset sprocket will I need? Will I have to mod my frame? Will I need to offset the wheel at all?

Next year, the front end will get done. But until then, let's focus on the rear

Any and all tips are VERY appreciated and welcomed here to make it a smoother process

Devin

I would suggest doing front and rear together. Your front end ride height will moste likely be changed with different forks and you wont want to have to redo your mono mount. It is a good winter project to do both. As far as sprocket offsets, from what I have learned so far is this.....Get you swingarm completely mounted in there with tire and then measure your offset. Tire width will make a big difference on offset. You may need to machine down your rear hub as well as run front offset. I'm not familiar with the Ninja tire size and swingarm setup to tell you exactly what you need. When you go into this type of stuff it is almost all trial and error. Search build threads for someone who has done the same swinger conversion as you are doing and find out what they did. Consider where you will put your battery once the monoshock is in your way. Start a build thread so we can see your progress and help make suggestions as you go. Good luck!

I've checked a few threads here, just waiting for a reply. I've also signed on to the 650.info site, and there's a few builds there.

As for doing both together, I may be tight on the funds for both. The swing arm I'm installing has +/- 2 inch dog bones on it, so I should have a bit of free play here. I'm looking at running a 180 on the rear, but we'll see what happens. I might also do a bolt- on mono plate if I need to move anything later.

From the builds I've read about, some just machine down the hub, others chop the frame a little, some do a mix of a hub machine and offset, etc.

I'll for sure keep a build thread going to keep everyone up to date.

Id compare the size of the front/rear tires on the ninja to the skinny little front tire on that stock 650 before laying it into any corners really hard,that could lead to a bad situation really fast.

Id compare the size of the front/rear tires on the ninja to the skinny little front tire on that stock 650 before laying it into any corners really hard,that could lead to a bad situation really fast.

The rear is an 18" that I can toss between a 160-180 on, and the front is a 17" that I can put a 120 on. What do you mean with laying it into corners? Just the overall handling?

with custom dog bones you can adjust your rear ride height however is needed after you do the frontend swap.

you pretty much have to attack these builds with the "i'm going to do whatever it takes to make it the way i want it" mindset.

do you care if your rear tire is exactly centered?

mine (1980 z1r) is offset 3/8's to the right with absolutely no ill effects to the handling,doing that allowed me to get away with no frame or cush drive mods.i run a 3/8's offset countershaft sprocket 520 o-ring chain and 190(or 200)mm wide rear tire.

some people want the front and back wheels directly in line,so they can sleep at night :lol: .

it is not exactly a one size fits all mod,

you have to be able to dig and figure out what it takes,then make it happen.

we are here to help.

leon

Leon,

You're a man of wise words- I really appreciate the support and help

As for being dead on centre with the front wheel, I could really care less. I would prefer if I didn't have to cut and weld my frame for chain clearance, etc. if at all possible. The rim I'm putting on it 5.5 inches wide, so I know I'll have some work to do. I have the entire rear end off the '99 ninja 900, so I should be able to make everything work smoothly once I have a starting point.

When it comes down to running a countershaft sprocket on the back, do I have to machine the hub down? Or what exactly is needing to be done here? I'm new to mods like this, but more than comfortable in the garage.

Thanks guys!

Devin

650mod wrote: The rear is an 18" that I can toss between a 160-180 on, and the front is a 17" that I can put a 120 on. What do you mean with laying it into corners? Just the overall handling?

I mean with the stock skinny little 650 front wheel if you only do rear wheel,a real wide rear could tend to push a skinny little 19/100 tire screw a corner if youre hitting it hard

Oooh good call... I may have to bite the bullet and do the front too. It's not too hard of a conversion, just gotta have the cash

Ive got a 23 t-bucket that gets out 1-2 times a year,I know all about wide ass rear rubber pushing skinny front wheels through corners! :sick: :woohoo:

wireman has some wise words.
once you do any kinda mods you need to shake it down and get a feel for how it is going to handle.
before you can really trust what it is going to act like when you go to stuffing it into corners.
i have done the 190/200mm rear tire(i've ran both on the same wheel)conversion and still run my stock skinny front tire and scrape both sides a couple times a summer.



but,
you can bet your a$$ that the first couple times i was riding it i didn't just go into corners and throw it at the pavement and screw the throttle on :lol: !




i do now tho :evil: :whistle: ,

leon