Front Sprocket KZ750B

I need a little sprocket education. I'm replacing the front sprocket on my 1979 KZ750. The stock sprocket has a hole in it for a tab on the sprocket lock washer to fit in.

I'm looking at pics and diagrams of sprockets advertised as fitting this bike and a lot of them don't seem to have the hole. The JT/Emgo sprocket sold by Z1 (and other retailers) for example.

Then there the sunstar sprocket which does appear to have the hole.

Am I wrong about the JT/Emgo? Does it have the hole, they just don't show it in the diagram? They are all over the place at lots of retails and advertised as fitting my bike. I just want to be sure. Anybody used one of these before?

TBH you dont need the hole, the lock washer is enough on a modern ZX10R Ninja to stop it coming off so the twin will be fine!! Iys a kind of braces AND belt scenario. I'm also running 520 speockets & chain. Again, if they'll cope with a well ridden ZX10's power they'll do my Twin fine!


PS - The lock washer im talking of is off a modern Kawasaki, they fit fine & are cheap. My 07 ZX6R race bike uses them. Just install, tighten the sprocket nut & then bend the edge of the lock washer over the sprocket nut so it cant move

As 750steve said, the hole does not serve any purpose in this application. On my 1982 KZ650, there is a washer under the nut, and it has teeth on the inside diameter that fit the splines on the shaft, thereby keeping the washer from turning on the shaft. After installing and torqueing the nut, you bend the outside lip of the washer over one of the 6 faces on the nut. This keeps the nut from ever unscrewing.

Incidently, I have a 14 tooth front sprocket that I would like to trade for a good 13 tooth, if anybody is interested. It is a JTF518-14T, for a 630 chain, purchased from Z1 Enterprises. Also, I need a replacement nut. Some goofball (me) tightened the nut so much last time that I had to grind it off to get it loose.

The hole is needed only if you have the original (obsolete) type of lockwasher which had a tang that fit into the hole. Most washers don't, they just bend over a flap of metal against the flat side of the nut. Chances are you don't need the sprocket with the hole.

Topper, tab on nut flat is sufficient, going on 4 years no problems
16 tooth (original size)



17 tooth (+1) about 500 RPM drop at 65 mph
18T (+2) requires guard removal



Jim

What front sprocket lock washer do you guys use with replacement sprockets?

I got a 17T sprocket from Z1. The original lock washer had that little tab on it that fit into a hole on the sprocket. The new sprocket doesn't have a hole for that tab. The guy at Z1 said I needed a splined lock washer but he didn't have one in stock.

Is this something I can pick up at a local dealership? Or do I need a lock washer from another year Kaw?

Of course if I look up lock washers for a '79 KZ750 they're not splined and have that tab. So what do I need to be looking for?

I guess if push came to shove I could reuse the lock washer that the PO put on when he upped to the 18T sprocket. But I'd really rather not.

Topper, I reused the original washer on mine.
You might take the old sprocket with you to a local shop and see if they can match the splines to a later model lock washer.

Jim

Topper, may I ask why you are replacing the 18t? I was planning to get on myself to drop the RPMs way down. Too underpowered? I figured with all the torque it would be fine.

damarble wrote: Topper, may I ask why you are replacing the 18t?

Here's why: kzrider.com/forum/5-chassis/529642-sproc...fe-expectancy#530060

With an 18T sprocket even the slightest amount of chain slack allowed the chain to rub against the clutch push rod and transmission cover.

Rainman wrote: Topper, I reused the original washer on mine.
You might take the old sprocket with you to a local shop and see if they can match the splines to a later model lock washer.

Jim

I was a little leary of reusing the lock washer but maybe I could get away with it. I just figured it can't be but a couple bucks if I can find one.

Taking the sprocket to a local shop is a great idea and I can do it with the new sprocket so I have all the parts on hand when I take the sprocket off.