Why Should I do this?
The Seca II came from the factory with a rear wheel that is 18" in diameter and 3.5" wide at the rim. This wheel uses a 130/70R18 rear tire. This is a legacy wheel and tire size and not many manufacturers support tires in this diameter anymore. The tires that are available in this size tend to be bias-ply technology. Common tires included Bridgestone Battlax, Michelin Pilot Activ and Kenda Cruiser. If you want to run modern tire technology: radial banding, multi-density rubber, multi-condition siping, etc; you're nearly out of luck.
I have been using a Yamaha FZR600 rear wheel for the past few years. This wheel is a direct-swap for the stock 3.5” wheel and allows me to run a 150-series tire; specifically, 150/60R18. As with the Seca II, however, this wheel is 18" in diameter and there are only two tire options available: The Bridgestone Battlax and the Shinko Podium.
If your bike is due for new tires, installing a 17" rear wheel will allow you to run common tire sizes and will allow you the option of choosing modern tire technology.
The wheel of choice is the Suzuki RF600/Bandit 600 rear wheel. This wheel is 17" in diameter with a width of 4.5" at the rim. This wheel allows you to run a common 150/70 or 150/60 series rear tire. The hub spacing on the RF600 rear wheel is narrower than the Seca II wheel, ensuring that the wheel will fit in the swing arm without machining the hub. The spoke pattern on the RF600 wheel is similar to that of the stock wheel. The wheel weighs 2.6 pounds less than the stock wheel. Most importantly, RF600/Bandit 600 rear wheels are plentiful and generally inexpensive.
There are two ways to do this swap: One way uses the stock Seca II rear caliper/bracket and adds a spacer between the caliper bracket and the swing arm. The other way uses a Bandit 600 rear caliper bracket and GS500 rear caliper. The later method is much cleaner and has fewer compromises and is the one I went with.
What parts will I need?
- 1994-1996 Suzuki RF600 (1996-2000 Suzuki Bandit 600) curved spoke 4.5" wide 17" rear wheel
2005+ Suzuki GS500F cush rubbers
2005+ Suzuki GS500F sprocket carrier assembly w/ bearing, oil seal, bolts and carrier spacer
1996-1999 Suzuki Bandit 600 (1998-2005 Suzuki Bandit 1200) rear caliper bracket
2005+ Suzuki GS500F rear caliper with pads
2005+ Suzuki GS500F rear caliper torque arm
1979-1983 Kawasaki KZ400/KZ440 lefthand rear axle spacer (17x35x19.5) (Kawasaki P/N 92027-1197)
2008-2012 Kawasaki Ninja 250 righthand rear axle spacer (17x28x15) (Kawasaki P/N 92152-0844)
- 150/60R17 or 150/70R17 rear tire
(2) 17x47x14 double-sealed axle bearings, type 6303-2RS (this is the stock Seca II rear bearing size)
(1) 17.2x25x97mm bearing spacer (Kawasaki PN 92143-1119 or PN 92027-1993)
(1) 28x47x7 oil seal (this is the stock RF600 right-hand rear oil seal size)
(1) 35x62x8 oil seal (this is the stock GS500F left-hand oil seal size)
(1) Suzuki Gladius (SFV650) JTR823 46T or 49T rear sprocket
(1) Radare's fancy-schmancy 3mm sprocket spacer (OR five 10mm ID by 3mm thick spacer washers)
(1) 17" long rear brake hose with 90-degree offset, straight 10mm banjo ends and (4) 10mm banjo-bolt washers
If you plan to use the Suzuki rear brakes, expect to spend around $300 to do this one right, including the cost of the tire. Using your Seca II brakes will save you about $100 but is a compromise.
Fitting the Rear Wheel:
Swing Arm Widths:
The Seca II swing arm measures 228mm (9") at the rear axle. The total stack up on the RF600 rear wheel, with the GS500 sprocket carrier, is 175mm at the center of the hub, leaving 53mm of space for the wheel spacers and the brake bracket.
Wheel Spacers for 17" Wheel
After many measurements, reconfirming thicknesses and modeling the rear suspension, the following spacers are needed for centering the RF600 rear wheel in the Seca II swingarm:
For reference, the stock Seca II wheel spacers have the following measurements:
- Right-hand Spacer (Rotor-side): 17x25(30)x13
Left-hand Spacer (Sprocket-side): 17x35x13
Left-hand (Sprocket-side) Wheel Spacer: 17x35x19.5 (Kawasaki P/N 92027-1197). This is the stock left-hand rear axle spacer for a 1980-1983 Kawasaki KZ400/KZ440.
Right-hand Inner (Rotor-side) Wheel Spacer::
- If using Seca II brakes, the stock Seca II right-hand wheel spacer, 17x25(30)x13 (Yamaha P/N 90387-177Y4-00) should be installed between the wheel and brake caliper bracket. This spacer will perfectly align the brake caliper bracket to the RF600 rotor. A 7mm spacer will need to be installed between the Seca II caliper bracket and the swing arm.
If using Suzuki brakes, a 14mm thick spacer is needed between the wheel and caliper bracket. The Ninja 250R right-hand spacer is 17x28x15 and should be ground down to 14mm thick giving a final dimension of 17x(28)x14. This will properly align the RF600 rotor in the GS500 caliper.
The Suzuki RF600 rear wheel uses a 20mm rear axle while the Seca II rear axle is 17mm. Replacing the rear wheel bearings on the RF600 wheel with Seca II rear wheel bearings will allow the 17mm axle to fit. Seca II rear wheel bearings are 17mmx47mmx14mm (17x47x14).
When installing the new wheel bearings, a new bearing spacer must be used as the one in the RF600 wheel is too large in diameter. The RF600 spacer is 97mm long. I found that the bearing spacer from a 2004 Kawasaki Ninja 250 is an appropriate replacement and fits the 17mm axle. The Kawasaki spacer measures 17.2mm x 25mm x 97mm (Kawasaki part number (P/N 92143-1119). Alternatively, you can cut down a length of 3/4" Schedule-80 steel pipe to 97mm in length and use that as an axle spacer.
The Suzuki GS500 sprocket carrier and sprocket carrier spacer are already sized for the 17mm axle and require no modification.
The Bandit 600 brake caliper bracket is sized for the 20mm axle and must be shimmed for use with the 17mm axle. A length of 17x20mm tubing, lightly pressed into the bracket will allow it to be used with the 17mm axle.
Bearing Oil Seals:
The following oil-seals should be used to seal the wheel:
- Left-hand: GS500E/F left-hand oil seal, 35mm x 62mm x 8mm (35x62x8)
Right-hand: Because different spacers are used on the right-hand side depending on what brake setup you choose to use, there are two possibilities for the right-hand oil seal:
- If using the Seca II rear brakes: Use a Seca II right-hand oil seal, 25mm x 47mm x 7mm (25x47x7)
If using Suzuki rear brakes: Use an RF600 right-hand oil seal, 28mm x 47mm x 7mm (28x47x7)
- If using the Seca II rear brakes: Use a Seca II right-hand oil seal, 25mm x 47mm x 7mm (25x47x7)
The RF600/Bandit 600 rear wheel uses a rotor which is 5mm thick, fits an 84mm hub with a 110mm diameter 5-bolt pattern and is 240mm in diameter. The Seca II rear rotor is 4mm thick, fits a 115mm diameter 6-bolt pattern, and measures 245mm in diameter. After many hours of searching the interweb, I was unable to find a 245mm rotor which would fit the RF600 bolt pattern. A 245mm rotor that fits the RF600 bolt pattern is unavailable. So you have two options: You can use the Seca II rear brakes and live with the pad misalignment OR you can install Suzuki rear brakes.
Using Stock Seca II Brakes:
The Seca II rear caliper bracket and rear caliper can be used but because of the differences in diameter of the rear rotor, the Seca II pads will sit 2.5mm further upward on the RF600 rotor. This pushes the pads upward and 2.5mm of brake pad will extend beyond the outer edge of the rotor. This will cause the pads to wear a notch in their upward edge as they wear on the rotor.
Wheel Spacer: If using the stock Seca II rear brakes, use the stock right-hand Seca II rear spacer. This spacer measures 17mm x 25 mm and is 13mm thick. Additionally, a 7mm spacer will be needed between the bracket and the swing arm. A 17x29x7mm spacer is available from Kawasaki and should work nicely (Kawasaki P/N 92143-1777). This spacer will require a 25x42x7 oil seal.
Torque Arm: The Seca II torque arm will work with the wider wheel if a 150 series tire is used. Any wider and the tire will rub on the torque arm. In this case, modify the torque arm by bending it outward at the outer diameter of the tire.
Using Suzuki Brakes:
The better solution for rear brakes is to install a Bandit 600 rear caliper bracket and GS500F rear caliper. This setup aligns the pads properly, centers the rotor appropriately and eliminates the need for a second spacer on the right-hand side. Reducing the number of spacers is a good thing; it'll save you a ton of grief when installing and aligning the rear wheel. To install Suzuki brakes in the Seca II swingarm, you'll need to do a few things:
Wheel Spacer: To properly align a GS500F caliper to the RF600 rotor, you'll need a wheel axle spacer that is 14mm thick. This centers the rotor in the caliper and aligns the pads correctly. Grind down a Ninja 250R right-hand spacer down to 14mm (17x28x14) and install this between the wheel and the caliper bracket.
Caliper Bracket: The caliper bracket for a 1996-2000 Bandit 600 is 36.5mm thick at the rear axle and is perfect for this conversion. With the RF600 rear wheel properly centered and the 14mm spacer installed against the right-hand wheel bearing, there is 34mm of clearance between the spacer and the swing arm. Machine (sand/face/grind) the bracket down to 34mm thickness at the rear axle. I used my belt sander and frequently checked my progress with a digital caliper until I was down to 34mm.
Because the Bandit 600 uses a 20mm axle, a 17x20mm shim should be pressed into the axle hole on the bracket to allow it to properly align with the rear axle.
Torque Arm: The GS500F caliper uses a 16mm thick torque arm mount. A Bandit 600 torque arm fits this caliper and routes nicely around the wider 4.5" wheel. This torque arm is quite a bit wider at the swing-arm end than the Seca II swing arm mount. The Seca II mount is 10mm thick while the spacing in the Bandit 600 torque arm is 20mm. A 10mm ID by 10mm thick spacer should be installed between the outer-edge of the Bandit 600 torque arm when fitting it to the Seca II swingarm.
Rear Brake Hose: The Seca II brake hose can be used with the GS500F caliper by rotating the rear banjo 90-degrees. This does put quite a twist on the hose and is not ideal, however. I recommend using a custom braided stainless hose. You'll need one that measures 19" from banjo-bolt to banjo-bolt, that uses 10mm straight banjos and that has a 90-degree offset between banjos. I used a 16" Goodridge Shadow brake hose and two 10mm straight banjo ends. The Goodridge banjos screw into the hose and can be aligned at any orientation which works well for this purpose.
Chain, Sprockets and Tires:
The stock chain centerline must be maintained when swapping wheels to minimize chain wear and ensure reliability. The Seca II sprocket sits 19.5mm from the edge of the swing arm on the stock wheel. With the RF600 wheel properly centered in the Seca II swingarm and a GS500F carrier fitted, there is 22.5mm distance between the sprocket and the swingarm.
Here is a photo of the two sprockets side by side: The RF600 sprocket is on the left; the XJ600 sprocket is on the right. Note that there's about a 3mm difference; the XJ600 sprocket sits 3mm further out than the RF600 one does.
A 3mm spacer installed between the sprocket and the GS500F carrier will shift the chain back into proper alignment. 3mm shimming washer can be used to move the sprocket outward; alternatively, I have made a small batch of custom sprocket spacers.
Here's the sprocket shim I had made; this one is 0.125" or (3.18mm) thick (I have one of these left; if you need one, PM me and I'll send it to you, free of charge):
Here's the second side by side, this time with the shim installed. The RF600 sprocket is on the left; the XJ600 on the right. With the shim installed, the chain-line should be appropriate:
The Suzuki GS500 sprocket carrier supports a JTR823-type sprocket. This sprocket is used on the GS500E/F and the Suzuki Gladius and is available in the following sizes: 39, 41, 45, 46 & 49 tooth. The stock sprocket sizing for the GS500 is 39T while the stock sizing for the Suzuki Gladius is 46T. Because of this, the 39T and 46T sprockets are most prevalant while the 49T sprocket is much more difficult to find. I chose to install a 46T sprocket mainly due to availability.
Based on the ratio of tire circumference to sprocket circumference, the following sprockets are recommended:
- If using a 150/60 tire, a 46T sprocket should be used for near-stock gearing.
If using a 150/70 tire, a 49T sprocket for near-stock gearing.
The stock Seca II chain is a 520-pitch chain, 110 links. If using a 46T sprocket, the chain will need to be shorted two links to a total length of 108 links.
The stock tire size for the RF600 is 160/60R17. This tire is too wide for the Seca II and will interfere with both the chain and the rear brake caliper torque arm. It is recommended that a 150/70R17 or 150/60R17 rear tire be used with the RF600 rear wheel when installing it on your Seca II.
Here's the RF600 wheel aligned in the stock swingarm with spacers: Click image to enlarge:
Modifications to Stock Parts:
As mentioned above, some of the new parts will need to be modified to work appropriately with the Seca II swingarm. These include:
- Cut down the Kawasaki right-hand spacer (17x28x15) to 14mm total thickness to work with the Bandit 600 caliper bracket.
- Cut down the Bandit 600 caliper bracket to 34mm to fit between the RF600 wheel and the spacer.
- Sleeve the Bandit 600 caliper bracket with a 20mmx17mm sleeve to work the the Seca II 17mm rear axle
The Kawasaki 250R right-hand spacer needs to be trimmed down to 14mm to properly align the Bandit 600 caliper with the brake rotor. To do this, I used a right-angle welder's magnet and a chop-saw with a metal cut-off disc fitted. The magnet sticks firmly to the base of the chop-saw and holds the spacer firmly at a right angle. I then lowered the cut-off wheel and carefully pressed the spacer into it to remove material.
I removed material slowly, checking the thickness of the spacer frequently and checking it at 4 or 5 points around the spacer to ensure that I was removing material evenly. I ground the spacer down to 14.1mm thick and then used a piece of 220-grit wet-or-dry sandpaper on a pice of glass to sand the spacer smooth. Again, I frequently checked the thickness at multiple locations to ensure that I was removing material evenly. When done, I had a spacer that measured 14.07mm thick and was consistently flat to 0.03mm.
Cutting down the Bandit 600 Caliper Bracket to Fit
The Bandit 600 caliper bracket is 36.5mm thick at the axle. The space between the wheel and swingarm on the Seca II is only 34mm. The Bandit 600 caliper bracket must be cut down to 34mm to fit between the wheel and swingarm. Remove material from the swingarm side of the bracket as you want to keep the stock finish on the wheel side. To do this, I used my belt sander turned upside down. I sanded the bracket in 90-deg rotations and frequently measured the thickness to ensure I removed material evenly. I sanded the spacer until it was 34.1mm thick. I then used 220 grit wet-or-dry sandpaper to final sand the bracket, again measuring frequently to ensure I was removing material evenly. I sanded until the bracket was 34mm thick.
Cutting the Sleeve for the Bandit 600 Caliper Bracket
The Bandit 600 caliper bracket is sized to accommodate a 20mm axle. Since the Seca II uses a 17mm axle, this hole must be sleeved to ensure the caliper bracket is aligned appropriately. I purchased a length of 17mm O.D. by 20mm I.D. titanium (yes, titanium) tubing on EBay from China for $20. I then cut a length of that tubing to 34mm using my chop saw. I carefully ground the edge, rotating the tubing as I ground it.
Once I had the spacer consistently 34mm in length, I used a piece of 220-grit wet-or-dry sandpaper and a piece of glass and wet-sanded it down to 33.8mm. This will ensure that the sleeve does not extend beyond the thickness of the caliper bracket.
This sleeve is about 0.25mm smaller in diameter than the hole in the caliper bracket. It will slide nicely into the caliper bracket but can also be easily removed. To ensure that it stays put, I coated it
with a light coating of JB Weld Epoxy and slid it in place. The epoxy will take up the difference in diameter and will keep the spacer from falling out.
Bolting it All Together:
Here's a general step-by-step showing what is required to install the 17" wheel.
Beginning with the bare wheel (rotor and cush drive removed), use a screwdriver to remove the oil seal:
Use a drift and carefully tap-out the sprocket-side bearing. Move the drift around the bearing, tapping it evenly on all sides to prevent cracking the wheel hub:
Here's the hub with the bearing removed:
After the bearing is removed, the bearing spacer will fall out. Here's a comparison between the RF600 bearing spacer and the Kawasaki bearing spacer we'll be using:
Using the same technique, tap out the bearing on the rotor side. Here's the hub with the bearing removed:
Here are the new bearings, new bearing spacer and new oil-seal as mentioned above:
Go to your local hardware store and pick up some hardware to press in the new bearings with. I used a 8" x 5/8" bolt, pair of 5/8" washers and a 5/8" nut:
Lightly coat the outer shell of the bearing with axle-grease and tap it lightly into place to get it started. Insert the bearing spacer and then do the same with the other bearing. You will press both bearings into place at the same time. Here's the bearing with the outer shell lightly greased and tapped into place (started):
Grease up the bolt and insert it through the axle hole. Grease the washers/nut and thread in place. Use a pair of box-end wrenches and slowly/carefully press the bearings into place. Stop periodically and check to ensure that both bearings are being driven in and that they are being driven-in squarely:
Here's the rotor side bearing pressed into place:
And the hub-side bearing:
Lightly coat the oil-seal with axle grease and press it into place using your thumbs. The seal should easily press into position without the use of tools. Work your way around the seal and ensure it is fully seated:
If you are using one of my sprocket shims, lightly push it into place:
Install the sprocket and bolt in place using the RF600 sprocket bolts and nuts. Torque the bolts to ## ft-lbs:
Here's the sprocket with shim installed:
Apply thread-locker blue to the rotor-bolt threads and install the rotor. Torque the rotor-bolts to ## ft-lbs:
Here's the rotor, fitted:
Lightly coat the cush-drive rubbers in silicone tire-shine and pop them into place. There are five (5) cush rubbers total:
Grease the sprocket carrier bearing with axle grease. Work the grease into the bearing and roll the bearing to ensure it is well lubed:
Lay the sprocket carrier into place. Press your palms downward on the sprocket and rock the carrier; it will fall into place. If it does not, apply a light-coat of silicone lubricant to the backside of the carrier and try again:
Fit the rear axle bolt through the swingarm and slide the rear brake caliper bracket in position. Allow the axle bolt to hold the caliper bracket:
Apply a coat of axle grease to both wheel spacers and install them in the wheel. The grease will help hold them in place. Using your knees to help hold the wheel, carefully slide the wheel into position. It WILL be a tight fit given the tolerances of the spacers used. Once the wheel is aligned, slide the rear axle bolt through it. Here's the wheel installed in place:
Install the rear caliper, rear caliper stay and new rear brake line:
Your stock chain needs to be shortened to 108-links. Using a Dremel or grinder, grind off the rivets for the link two from the end as shown below:
Carefully pop-apart the chain and remove the extra links. Save the links and O-rings in a zip-lock back for future use (if needed):
Lubricate the master-link and install the chain. Tension the chain as you typically would and lubricate the chain/sprockets with a good-quality chain lube.
Torque the rear axle bolt to ##lbs and install a new cotter pin.
Here's the finished conversion: