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VMAX Rear End Swap


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VMAX Rear End Swap

by: Don Nelson

 

Shortly after purchasing my Royal Star Venture in 1999, I realized that 5th gear on these things are very high. At the time, I just accepted it but after a recent trip to Colorado riding two up, pulling a trailer and fighting some heavy headwinds, I made up my mind that I was going to look seriously for a solution.

 

On that trip, I did a little experiment. First I asked a rider of a first gen Venture what kind of RPMs he was running at 70 MPH. He replied that he was running right at 4,000 RPM. When we got back on the road, I checked my tach only to discover that I was actually running exactly 4,000 RPM in 4th gear. When I shifted to 5th, the RPMs went down to about 3200 RPM and I felt that I was really lugging the engine with the load I had and running 70 MPH. So, for a full tank of gas I stayed in 4th gear and was running the 4,000 RPMs. At the next gas stop, I checked with Bob Dakin as to how much gas he put in. Bob also rides an RSV and was running in 5th gear. It turns out that he and I need the exact same amount of gas even though I had been running in 4th gear. I knew then that the only reason I would have used the same gas as him was because that in 4th gear, I was staying in the power band of the engine, not lugging it.

 

Upon returning home, I sent John Furbur and email and found that he does offer a VMAX rear end swap for the RSV. A few days later, my new rear end arrived in the mail and was installed a couple of days later. After getting the rear end installed and taking the bike for a test run, I am pleased to say that it does exactly what I hoped it would. I am now running about 500 RPM higher in every gear. In 5th gear, I now run 3600 RPM rather than the previous 3100 RPM. This is a good compromise between the 4,000 RPM that I had run in 4th gear and the 3100 that I had previously run in 5th. I have not yet had time to take a long enough trip to check the gas mileage again but I really expect to see an improvement when riding two up and especially when pulling a trailer also. Regardless of the fuel mileage though the increase in performance of the bike is enough that I am even willing to sacrifice a couple MPG if that is the case. I have tried various exhausts, K&N filters and the Dyna 3000 Ignition module but none of those have come close to giving me the performance increase as this rear end swap.

 

I promised to do a write-up on the install so here it is. The truth is though, if you have ever pulled your rear end to lubricate the drive shaft, then you have really already done this job. You simply replace the stock rear with the VMAX rear. Very simple job.

 

Since there are already instructions posted for removing the rear wheel, I will start this procedure at the point where the saddle bags, rear wheels and mufflers have already been removed.

So here we are at that point. The first thing you will want to do is drain the rear end.

 

http://www.venturerider.org/vmaxrear/100_1399%20%28Small%29.jpg

 

Remove the one screw that secures the speedometer sensor to the rear end.

 

http://www.venturerider.org/vmaxrear/100_1401%20%28Small%29.jpg

 

After the screw is removed, the speedo sensor just pulls out. There is an O-Ring so you have to pull on it fairly hard.

 

http://www.venturerider.org/vmaxrear/100_1402%20%28Small%29.jpg

 

Remove the 4 acorn nuts that secure the rear end to the drive shaft tubes.

 

http://www.venturerider.org/vmaxrear/100_1403%20%28Small%29.jpg

 

Slide the rear end off. The drive shaft will come out with the rear end.

 

http://www.venturerider.org/vmaxrear/100_1404%20%28Small%29.jpg

 

Here is the assembly removed.

 

http://www.venturerider.org/vmaxrear/100_1405%20%28Small%29.jpg

 

You then need to pull the drive shaft out of the rear end. There is nothing it in except for an 0-Ring so you have to pull on it fairly hard but it will come out.

 

http://www.venturerider.org/vmaxrear/100_1406%20%28Small%29.jpg

 

There is a spring inserted in the rear end that you will need to remove and insert into the new rear end. It just pulls off so pull it off and install on the new one.

 

http://www.venturerider.org/vmaxrear/100_1407%20%28Small%29.jpg

 

http://www.venturerider.org/vmaxrear/100_1409%20%28Small%29.jpg

 

While you have the drive shaft out, now is the time to grease it up before putting it all back together.

 

http://www.venturerider.org/vmaxrear/100_1410%20%28Small%29.jpg

 

Install the new rear end with drive shaft. It is recommended that you now install the rear axle, without the wheel, and do the rear end alignment as outlined in the Yamaha TSB. This procedure can be found here:

http://www.venturerider.org/forum/showthread.php?t=1705

 

http://www.venturerider.org/vmaxrear/100_1412%20%28Small%29.jpg

 

http://www.venturerider.org/vmaxrear/100_1413%20%28Small%29.jpg

 

Now is a great time to grease the rear drive pins in the wheel hub. See this excellent write-up by Tartan Terror for that procedure. http://www.venturerider.org/forum/showthread.php?p=117809#post117809

 

Now you can follow the normal procedure and re-install the rear wheel. After the wheel is installed, tighten the axle nut to 110 ft.lbs..

 

Now you are ready to fill the new rear end with lube. I use Mobil 1 synthetic but that is just my personal choice. As you can see, I filled the rear before re-installing the rear wheel so you can actually do it either way.

 

http://www.venturerider.org/vmaxrear/100_1414%20%28Small%29.jpg

 

That's it folks. You now have VMAX gearing in your RSV, Royal Star or Venture. Blue Ridge Mountain Sportmax offers the VMAX rears for all our bikes so if you are interested John Furbur at http://rmsportmax.com/gateway.html

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