A Hondasaki final drive

This is about grafting a Honda GL1200/1500 final drive to a ZN1300 Voyager's swingarm.

A brief update on the history of this project here. Tony (Lucasind) didn't like hearing his Voyager 1300 "screaming" at 4000rpm at 70mph, and was trying to find a set of higher-ratio final drive gears for it. Not gonna happen! So, the alternative was to find an existing drive with the appropriate gear ratio. The Voyager 1300 has a 3.40 ratio, and the '84 Gold Wing has a 2.833 ratio. Both are right hand mounted, so they spin the same direction. In theory, by calculation, the Honda drive will give 3333rpm at 70 mph. Another requirement was that the shock mount had to be positioned to at least give me options for making an adapter to correctly position the stock Voyager shock's lower end.

So, since all final drives/rear wheels have a unique coupling, I bought the whole rear end from an '84 Gold Wing, including the swingarm, driveshaft, final drive and rear wheel. The project is to swap everything onto the Voyager's swingarm, then blend the front half of the Voyager's driveshaft to the rear half of the Honda's.

To start I cut the flange that mounts the final drive to the swingarm from each bike's swingarm. Each flange is a machined casting with a short nose that centers it in the swingarm's right tube, then it gets welded full circle around the tube. Simple! I cut the tube right along the weld on each swingarm without cutting all the way into the flange casting. Once it was thin enough I knocked the flange off with a leather mallet. Did this on each swingarm.

The Honda flange has a slightly larger diameter nose, by about .150", so I cut it down by about .130" because the Voyager's flange actually wiggled a bit inside the Voyager tube. The Honda flange now fits perfectly inside the Voyager's right swingarm tube. I also cleaned up the remaining weld on the flange while I had it in the lathe. I was worried about making the nose on the Honda flange too thin by turning it down to fit, but it turned out to be the same thickness as the nose on the Voyager's flange. It also tapers a bit to become thicker as you move from the edge of the nose.

So, we are now at the rough-cut stage. Next I need to make a jig to align the axle with the swingarm's pivot points, and at the Voyager's original span from pivot to axle. Once this jig is made I can weld the Honda's flange to the Voyager's swingarm tube. Then I need to assembled the whole thing to fit the Voyager's brake caliper to the Honda's rear wheel/rotor. I'm hoping it will only be a matter of a shim to correct side-to-side positioning from the Voyager's stock position. They both use the same diameter rotor. I also will have to make up a new axle spacer to fit the Honda rear wheel in the Voyager's swingarm.

I have recently learned that the GL1500 final drive is the same ratio as the GL1200 that I am using for this swap, but that the 1500's rear wheel has much more robust bearings and overall much stronger. So, I will finish the swap using my existing 1200 parts, but will do a further swap using GL1500 components.

Here are just a few pics of progress so far. The complete set of pics can be seen at the link below. The gold final drive is the stock Voyager drive, and the silver one is from the '84 Gold Wing.

www.flickr.com/photos/7789950@N05/sets/72157649688788019/

That's a really interesting project you've taken on. I admire you for it! I look forward to reading about your progress, and the challenges you encounter along the way.

I can smell the changing of the steel all the way here to Toledo ! Thanks for that update post.

I love this kind of stuff ! Outstanding ! "Necessity is the Mother of Invention". ....and it certainly helps us get through the winter !

.....Yes, Like it or not......winter has set in here as well for the foreseeable future
Staying bizy is what us northerners do ! What are ya gonna do about it anyway ?
My 1300 is all back together, the new progressive rear shocks are assembled,and installed.......



They came disassembled, so after work one night I got the heaters going in the garage,and spent a few hours gettin er' done. WAY to cold to go out for a test ride this time of year .....cause when I do that, I usually end up sick too old to do something that dumb anymore !
So I pulled this moldy oldie out of one of the out buildings to stay bizy doing what Iv'e loved doing for the last 4 and a half decades.

I know it's not a 1300 ....but it bears the KAWASAKI badge,so in my opinion ,it's worthy of my attention !
Pretty neat story with this bike..... It was bought brand new in the spring of 85' and the owner rode it 1988 miles until a car turned left in front of him. He slammed the bike up the curb,and the bike did a 180 degree endover. The guy was injured seriously and went to the hospital with 2 broken collar bones, and broken ribs......the bike was towed to his farm, and the insurance company "totalled" the bike.
So there it sat outside of a barn ,on the edge of a soybean field from 1985....till I came along in 2012 and rescued her.
It is, and will be a long slow process in getting her roadworthy again..... but I will be thrilled to throw a leg over the seat ,and take her out for that "first ride" ....after a VERY long hibernation !.........................tony

Caution! Gonna ramble here a bit (a LOT!). But, first, my apologies to Bill for not paying attention and placing this thread in the wrong section. You are welcome to move it to the "projects" section.

Besides the story of why Tony and I conceived this drive there are lots of concerns that had to be satisfied before I chose the final drive to use, and even whether or not it could be done.

First I had to find a drive that had the right ratio to do what we wanted. Second, it had to be a right-hand mounted unit to spin the right direction. Third, the wheel that comes with the drive from the donor bike has to be a 16" to match the Voyager's. Fourth, I had to feel confident that I could fabricate a new lower shock mount adapter to fit the stock Voyager's shock in the stock location. Fifth, the flange at the end of the right swingarm leg of the donor bike had to be close in diameter to the one on the Voyager's swingarm so the donor flange could be swapped CLEANLY, without a lot of buildup or fudging.

The first issue was to find a drive with a ratio around the 2.7-2.9 range. The stock Voyager has a 3.4 ratio. There were five drives that I found with 2.73 ratios, but they were left hand mounted! BMW also has lots of different ratio drives, but a lot of them are left-handers or are just so weird in their mounting and shape as to make them unusable. It seems that most of the Jap bikes have a lot of similarities in their engineering styles, so a lot of the issues were easily overcome by using another rice-cruiser drive. Honda and Kawasaki both use 20mm axles almost exclusively on most of their bigger bikes, so that really helped. Brake rotors are also all pretty close in diameter, too. The main reason to use the same rear wheel as the donor bike for the drive is because the splined coupling system between the drive and the wheel for each bike is unique to that bike. They differ so much that adapting is not a practical option. So, the whole rear drive system, including the wheel, brake rotor, splined drive coupling, final drive, swingarm and driveshaft system are required, as well as a donor swingarm and driveshaft from a Voyager so you don't cannibalize the bike's original equipment (just in case you don't like the new drive!).

The Voyager 1300 is kinda special in this case. It's overall drive ratio (including the output ratio of the transmission) make it a nice road bike for the 55 speed limits we had when it was first marketed. But, now that we can drive 70 almost everywhere it needs another gear above 5th to keep the rpm's down to a reasonable level for sustained, all-day running. The engine has plenty of power to do this. It is yet to be seen if this will also increase fuel mileage when on the road. In theory, it should, because it will put the engine's power band at the right point for sustained 70-80mph running.

Doing the actual swap of the Honda final drive to the Voyager's swingarm is not hard at all if you have basic metal skills and good Mig welding skills. You also have to understand what alignment elements need critical attention, too. If you run a shaft through the swingarm pivot bearings, then another one through where the axle will be, they HAVE to be parallel, both vertically and horizontally. If they aren't, then the wheel will lean to one side or the other, or will not track straight with the front wheel, or BOTH! You will see how I achieve this alignment before welding when I post more pics. It's a pretty simple jig, but requires lots of checks, double checks, tack, check again, grind away the tack, re-align, check some more, double check some more, tack, and keep trying until it all lines up exactly. This is what it's like when just a one-off drive is made. If I do any more I will make up a hard-jig that will clamp everything down solidly for welding. No rework!

As for the brakes, the stock Honda rotor is the same diameter as the Voyager's, but not sure yet if it lines up side-to-side like the Voyager's. If it is a bit more inboard (toward the wheel) it will only need a couple of small spacers between the caliper and the bracket. If it is a bit more outboard, then I may have to make up a new offset bracket. Either way, it will allow the use of the Voyager's stock brakes so this will all be a quick plug-n-play installation.

Once the Honda's flange is welded onto the Voyager's swingarm, the Honda final drive is bolted up, the rear wheel is in place with new spacers and brake mount, the lower shock mount adapter is in place, then I will have to blend the two driveshafts together. The front half of the Voyager's shaft will be mated to the rear half of the Honda's shaft. Simple! Yeah, RIGHT! The u-joint at the front of the Voyager's shaft has no intended play, but the Honda's splined rear half gives me about 3/8" of play, total, fore and aft. The trick is to get it right in the middle of that 3/8", then check for position at full up and down movement of the swingarm. Once that length is finalized, the shaft can then be welded up completely. I will grind a 45 bevel on each end leaving just a 1/4" flat face on each to butt together.

Now I will talk about welding. I like to use a slow (VERY slow!) Mig weld technique that stops every 1/2" or so to cool. It takes hours to do, but it prevents altering the alloy too much of the steel in the immediate area around the weld. This method produces good penetration without the heat buildup. I can touch the weld immediately after stopping each time. Mig uses a very intense arc to melt the metal in a very small spot, imparting very little heat around that spot unless continued. Allowed to cool (about 30 seconds) before the heat builds up you get almost no change in temper or alloy of the metal, and no warpage, either. But, production shops can't afford the time to use this method.

Once the two shafts are welded together I will grind the weld smooth to eliminate any stress spots along a weld bead. Also, I will add a sleeve over the shaft to slip over the weld. This sleeve will be perforated to create a few plug-welds and also be welded along each end. These plug welds will be smoothed before the whole shaft is straightened and balanced. I don't have a balancer, so my local shop will have to do this.

I believe that driveshafts are hot-forged at the factory, so they end up with a fairly rough surface. Roughness is the playground of stress risers that cause cracks, so I may also grind the surface smooth and polish it lightly. I've seen two trike conversions that broke their driveshafts due to stress cracks at a rougher area of the shaft. That's enough to convince me to take the extra time to smooth things as much as I can.

Before tackling this project I had to learn that all shaft-drive bikes have several gearing reductions inside the engine/trans cases. The bottom line was to ignore all of the stats except for the final drive ratios. Overall ratios don't tell you how low the final drive is. I had to go to a Gold Wing forum to get the final drive ratios of their bikes, just to be sure. Then I had to find out what the wheel size was. Then I had to compare the diameters of the swingarm tubes right at the flanges. Then you have to look at the possibilities of mounting the shock. Then, I went to eBay to buy all of these components. I guess I lucked out and got a good, used '84 final drive, complete with the driveshaft. It's got very tight backlash in the gears. Not really TIGHT, but pretty close to perfect. Yhe seals don't appear to leak around the output of the ring gear. I learned the hard way that the pinion shaft is drilled through to the inside of the gear casing so gear lube flows forward into the driveshaft splines! Several Honda models use this lube method for their shaft drive bikes. Kawasaki uses grease on these same splines with equal success. After I pulled the Honda's splined shaft out of the coupling on the nose of the pinion, gear oil ran all over my pants and bench until I turned it up. I am going to be spot welding this hole closed on the pinion and using the Kawasaki method of greasing those splines!!!

Even with all of the care put into the driveshaft merger I am still not totally comfortable with it as opposed to a factory, uncut one. I would certainly not drop the clutch at full throttle on this bike! I would trust it to hold full power and a bit more. but, what more do you need on a cruiser? Besides, look at how many trike conversions are running around out there with shafts made this way. And, they are much heavier rigs with bigger engines (Honda GL1800).

OK, those are most of the thoughts that went into this project. Sorry for being so long-worded!