This thread will start out in the RSD....but after a bit of discussion and working out the bugs I will probably move it into the Tech section. I did this work a little bit at a time over the past 6 months, and unfortunately the photo documentation could have been better.
FRONT PULLEY
The stock front pulley is a 23 tooth pulley. The Kawasaki EN454 LTD used a 25 tooth pulley....which will decrease rpm's by 8% if used alone. According to the speed chart that Serowbot prepared 60 mph with the stock gearing would be 4,008 rpm....with the Kawasaki pulley it would be reduced to 3,688 rpm. This change will pull the rear wheel forward as a result of the larger pulley diameter - the change does work with the stock sized rear tire....oversize tires may not clear the swing arm. (RYCA bikes with 18" wheels cannot use ths pulley conversion without modifying the swingarm for tire clearance).
The Kawasaki front pulley costs about $ 80 new.
The Kawasaki pulley has a wider center hub and it needs to be machined thinner to work on the Suzuki. This can be done on a lathe if you have a way to hold the pulley - mine was done on a milling machine. The metal is very hard and a carbide tool was used to do the cutting.
Front of Pulleys
Back of Pulleys
The stock Suzuki pulley has the side flanges welded on, the Kawasaki pulley has tabs that are split and they stick out and are very rough - and they hit the engine case and pulley cover.
To provide more clearance I took a flat punch and hammered the tabs a bit flatter.
The rear post on the engine case interferes with the larger pulley, and has to be trimmed.
The bolt for the oil seal retainer has an extended bolt head and it can be replaced with pan head screw for more clearance.
Finally - You need to install the nut with threadlocker and a good lock tab washer, torque it to 94 ft./lbs. If you have a RYCA you will need to raise the front of the belt guard a little bit for clearance. On my outer cover I had to trim a small place where the outer flange just rubbed a bit on the outer cover - this support matches up with the one that had to be trimmed on the engine case
REAR PULLEY
The stock rear pulley is 68 tooth, and a Kawasaki KZ750 from around 1983 has a rear pulley that is 65 tooth. The combined change in the ratio is a reduction from 68/23 (2.95) to 65/25 (2.60) - which will reduce the 60 mph stock 4,008 rpm to 3,532 rpm.....a nearly 12% reduction.
You cannot use only the rear pulley in this conversion - as there is not enough travel for the belt adjustment to take up the slack caused by the smaller pulley diameter.
The Kawasaki pulley is cast iron......and weighs 2.4 pounds more than the stock pulley which is made from aluminum. It increases the rear wheel weight from 34 to 36.4 pounds....and I see no way to trim off any fat. The center bolt hole is larger than the Suzuki hole - so you have to make a spacer to take up the extra room and center the sprocket on the hub. The bolt circle is also different - so after I had the hub spacer made I installed the sprocket and marked the new hole locations, and drilled them on a drill press.
Kawasaki Pulley
Cutting out the spacer from an aluminum sheet
Trimming the inside diamter
Installed on hub and trimming the outside diameter
Once the pulley was on the hub......it then became necessary to trim the hub to correct for the difference in the pulley offset.
Trimming the hub to correct the offset
After I trimmed the hub and went to install the new pulley, I discovered the bolt threads did not extend deep enough allow the bolts to be tightened - so I had to install some washer on the outside. This winter I will make a proper looking plate to fit on the outside in place of the washers.
When I installed the rear wheel I discovered I had some play/wobble that I did not like......so I cut some strips of rubber from a floor mat and installed them. The wobble is gone.......now we will see how long that solution will last.
I also discovered that the smaller pulley would hit the left shock mounting bolt. I had to remove the bolt, trim the length of the hex head, and then plate the bolt and put it back on.
And this is what it look like installed.
There is just barely enough belt adjustment to make this work. On my Cafe' conversion I have about 1/2 turn left on the adjusters before I bottom out the axle in the swinge arm. This winter I plan on extending the swing arm table 1/4" and will make the slots a bit longer....while filling up some of the front of the slot. On a stock bike with normal length shocks it might provide a bit more adjustment room.
So far I have only gone on a 5 mile test ride as the weather has been too cold to ride much. I really think this is going to be a great change. It now becomes obvious when you shift into 5th gear. My rpms drop to 3,300 at 60 mph (18" rear wheel), and the engine is loping along and sounds great. There are hills in this area that most likely will require shifting into 4th to keep from lugging the engine too much. I am sure this conversion does not provide any higher top speed, and I expect that 4th gear is now the gear to use for speed runs, and 5th is now the overdrive for cruising. I am not sure how well this conversion will work on a stock engine/stock bike/saddlebags, large rider, riding double, etc. My bike has a Wiseco, Stage 1 Cam, better muffler, large foam air filter, etc, weighs about 320 pounds and I weigh 160....and the engine pulls this bike strongly with the new gearing. So far I am very happy with this change......now for the long term testing scheduled for the spring of 2014!