1982 Kawasaki GPz750 R1 chain/sprocket conversion from 630 to 530 pitch

Thought I share this. The GPZ750 R1 use 630 chain/sprocket pitch and it is getting harder to get. They are also normally non o-ring types which requires messy lubrication



To convert to updated 530 pitch the front sprocket, rear sprocket, and chain needs to be calculated.

Original 630 pitch:
Front: 13 teeth
Rear: 33 teeth
Ratio: 33/13 = 2.5

To convert to 530 system multiply by 6/5:
new Front: 13*6/5 = 15.6 ~ 16 teeth
new Rear: 33*6/5 = 39.6 ~ 40 teeth
new ratio: 40/16 = 2.5 ..... perfect

However I ride in the twisties often, and would like to have more acceleration instead of leisurely cruising speed. So I opted for larger rear sprocket (45 teeth)
desired new ratio: 45/16 = 2.8

Knowing that in the original ratio I cruise at 100kph at exactly 5000RPM the new RPM can be calculated:
old rpm * new_ratio / old_ratio
5000 * 2.8 / 2.5 = 5600
So with 13 Front and 45 rear, I would cruise at 100kph at 5600RPM

For the chain, I just buy 120 link o-ring 530 pitch chain and cut accordingly. 530 chains are much cheaper at $70 shipped from ebay.

After changing the chain, I felt that it is much quiter and smoother. And certainly easier to maintain in the long run with much less lubricant splatter. As predicted I now cruise 100kph at 5600RPM

Now hopefully I can keep up with that Z900RS :laugh:

photos:

16T front sprocket JTF513.16 available at Z1Enterprises but I bought it locally from PowerSport Kawasaki in Seaford


Rear Sprocket JTR488.45 from Z1Enterprises. This is the Emgo version which is much cheaper. If you would like to keep the stock gearing ration then the rear needs to be 40 Teeth ie. JTR488.40


Comparison between the sprockets. The front one is an exact match. The rear one is bigger as I had chosen it.


The front sprocket is tight, so no way to use a larger one like 17 or 18. It would hit the guard. 16 with 530 pitch is perfect.

I did the conversion on my GPz750 as well. Like Heavenly says, much quieter and smoother than the old, worn out 630 chain.
I went with the 41T rear with the 16T front to keep the ratio close to stock. At 65 MPH I am turning ~4,700 RPM which seems high to me. At 55 MPH I am at ~4,000 RPM which I would guess is where Kawasaki engineers wanted the cruising RPM to be given the speed limit at the time.
My cop bike is geared up some which puts cruise at 4,000 RPM which is comfortable.