Hi folks, today I want to cover an extremely important topic – how to make any heavy cossack motorcycle ride faster and be more fuel efficient. All this is done by simply changing your standard final drive gears with 10/35 gears.
In my article “Dnepr/Ural Final Drive: Its Maintenance and Repairing” I mentioned the possibility of installing 10/35 gears. I had known of such gears for some time, but I was happy with the 9/35 gears I had in my final drive and had no intension to change them. One day Doug Bingham, a fellow-biker from Washington, asked me to help him get the 10/35 set for his M-72 motorcycle (a nice and extremely rear motorcycle, btw). I found one dealer in Ukraine who offered 10/35 gears (for $40) and ordered one set for Doug. The dealer assured me that the gears were produced in Ukraine on some plant. This is a common situation for our country – when you have access to some local factory (you work there, your friends/relatives/etc. work there), you can have the needed part created from your drawing, for a small bribe fee, of course. I was a bit skeptic about the origin of the 10/35 gear set, because part of me thought the gears were of chinese origin, i.e. of poor quality. That was another reason why I wasn’t thinking of installing such a gear set on my bike. Once I got the gear set for Doug, I gave the gears to a friend of mine who works with metal and asked him to check their quality. The quality of the metal was very high and the geometry of the parts was not ideal, but good enough to be used. It was a pleasant surprise for me. I was so inspired by the results of this examination that I decided to buy myself a set of 10/35 gears.
The seller told me nothing about the installation process and it took me quite some time to complete it. I hated myself for messing with the 10/35 gears. I spent almost the whole night fighting with the final drive (I prefer to deal with such tasks at night) and asking myself “my standard 9/35 set was absolutely fine, why on Earth did I decide to mess with the 10/35 set?!” Finally, when the process was finished, the morning sky was bright enough for me to see all the imperfections of Ukrainian roads and so I went on the test drive…and I got the answer to my question, which was “because it is worth every single minute spent on installing it!” From the very first moment I felt a huge boost in speed. Riding on the first speed felt like riding on the second. I even started to use some clutch to prevent my rear wheel from doing a burnout.
After the test drive I wrote Doug that I “regret installing the 10/35 set…only now :)” Having a 17” rear wheel on my custom Dnipro, I get 60-62 mph (95-100 km/h) on the 3rd speed. The only downside of this upgrade is that I stopped using the 5th speed because that would be too much for our local roads. Riding my Dnipro-chopper 80 mph (130 km/h) and faster on a road full of waves and holes is close to a suicide and I’m not ready to check if Valhalla exists yet 🙂
A few days ago I found a speed chart for 8/37 and 10/35 gear sets and the data it offers I seems to be correct, because the results I got are almost identical to the ones mentioned in the chart.
Apart from the speed boost, installing the 10/35 gear set will make your bike more fuel-efficient, which is a nice bonus in any case.
If you ride your heavy cossack motorcycle without a sidecar, this upgrade is definitely in the list of the must-be-done stuff for your bike.
I had lots of troubles installing the set because of one reason – I was not prepared for the process. During the installation you will need a few gaskets and regulation shims. I was doing the final drive upgrade at night and had no chance to go and buy the needed stuff in a local motorcycle shop. That’s why I had to make new gaskets from a piece of paronite and new hub adjustment shims from a metal sheet I had near at hand.
For you to avoid the problems I faced, you should have these items before starting the upgrading process:
Now when you have everything needed, it will take an hour or two to complete the upgrade of your final drive.
The first step would be replacing a pinion gear with a new one.
The diameter of the 10 teeth pinion gear is slightly bigger than the diameter of the 8 and 9 teeth pinion gears. That’s why we need a drill and a burr. Using them you need to make the skirting smaller. Thus the hole will be wide enough for the new pinion gear. Aluminum is rather soft that’s why it won’t be hard to do this.
Once you are done with the pinion gear, it’s time to move to the second step – replacing a crown ring gear with the new one. Take off the hub, screw out the 8 bolts that keep the crown ring on its place, install the new one and assemble the hub.
Now it’s time to play with the gaskets and hub adjustment shims. Usually, there is one gasket and one shim, but the new gears have different geometry and require more distance between the crown ring and the pinion gear to operate smoothly. The shims help keep the right distance between the crown ring and pinion gears. When you push on the hub, the pressure goes to the shim and not to the crown ring. As for the gaskets, additional gaskets will prevent the cover causing additional pressure on the hub. If you install only 1 standard shim and 1 gasket, attach the cover and screw the nuts, the cover will press the crown ring gear down to the pinion gear. As a result the hub will be jammed. It might be able to rotate, but the incorrect position of the gears will lead to overheating when riding and excess wear of the parts. That’s why you will need to install several hub adjustment shims and gaskets so that the cover doesn’t press on the crown ring gear too close to the pinion gear.
In addition to the gasket and hub adjustment shim, you might also need to use a small shim on a pinion gear, if you want to make a sophisticated adjustment of your final drive.
You need to experiment a little to find the right position of the gears by assembling the final drive unit with 1, 2, 3, etc. shims and gaskets. The ideal position will allow the hub rotate easily, producing no crunching or any other strange sounds, and at the same time leaving no backlash (tiny backlash is fine) between the gears.
Once you find the right number of the shims and gaskets, assemble everything, using some high quality sealing product (I use this one), install the final drive unit on the bike, fill it with oil and get ready to be amazed with the results of this upgrade 🙂
If you face any problems with the process, please let me know in the comments below and I will try to help you solve them.