Aprilia

Aprilia RXV Rally

This is in fact the “Rally Bike build” part two, my new Aprilia RXV 550 makeover.

In the last few Dakar Rally’s the only serious opponent for the dominant KTM bikes were the two cylinder Aprilia’s.  In fact some say the engine of the Aprilia is the only 450cc engine which will last a complete Dakar, and on top of that it is more powerful than the single cylinder KTM. Rumors are that KTM is lobbying with A.S.O. to allow only single cylinder engines to compete in the Dakar. This would proof the superiority of this unique engine. Unfortunately the Aprilia off road sales department is not as successful as KTM and therefore there is no budget to invest in Dakar anymore. There top pilot Francisco “Chaleco” López Contardo signed at a brand new Italian team called Bordone Ferrari. His results in le Dakar on the Aprilia were 3-rd overall in 2010 and 4-th place in 2011. In 2012, his last year on the Aprilia, he crashed on the stage 7 and was out of the race.

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My choice for the Aprilia RXV is purely based on the engine and because I will not compete in Dakar I didn’t need to be limited to 450cc and went for the 550cc engine. Aprilia off road has stopped producing the 550cc and I got the last version of this model, recognizable by the red frame. Aprilia sells their factory rally replica bike engineered by the Aprilia Racing department complete or as a conversion as a kit, which specialist companies like Giofil in Italy and Behego in The Netherlands have used to convert standard Aprilia RXV 450’s into rally bikes. This kit will set you back EUR 16.000,- (excluding labor and the donor bike) A complete bike costs EUR 37.000,- I decided to make the rally conversion myself.

For smaller rally’s I want to keep the bike light and will not need the extra fuel capacity of the Dakar kit. All I’ll do is swap the standard fuel tank for a larger 12 liter (3 gallon) one. This way I can use the standard exhaust and rear frame. Downside is the limited autonomy of only 125 kilometers (about 75 miles) in competition. The front of the bike is very similar to the Factory bike because of the necessity of the same navigation equipment. In order to be able to read from your roadbook holder and tripmeter, both have to be placed high up on the navigation tower behind a proper fairing.  I was able to get my hands on an original fairing which was used in the Dakar 2011, refurbished it and took a mould. Now I can make my own.

First things on my list were the modifications: new wiring loop and the welding of the frame. The welding I commissioned to a specialized company called Lameier Photowelding here in Belgium. The new wiring was necessary in order to relocate the ECU and power regulator to the navigation tower. They were on top of the airbox not leaving enough space to change the airfilter properly. I placed them high up in the navigation tower together with the fuse box and horn which were also moved from their original position.

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I designed and fabricated the navigation tower with the original Aprilia rally bike as an example. In order to have maximum flexibility during the design process I used 4mm plywood for the prototype. After I had figured out the exact and best position of all the attached parts, I used the plywood plates as a mould for the final aluminum plates.

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The Aprilia RXV is quite an exclusive bike and as a result there almost no special parts suppliers available. I used several parts from Meca’Systems in France, one of the few companies which make some aftermarket parts for the Aprilia RXV.  I have found some compatible components designed for other bikes which will fit to my bike as well. For a larger front brake disc I used a Yamaha bracket (which also has Nissin calipers) from Braking. The navigation tower is held by two adapter plates from KTM and the BRP submount for the steering stabilizer is for a Honda which has the same top triple. I also used a Ducati oil cooler and a replica of a KTM rally front fender.

With a little help from the internet and creative thinking of some suppliers, I managed to get almost everything I needed for the conversion. Only the pin which carries the fairing had to be machined out of a piece of aluminum. The headlight brackets and light protectors are also handcrafted, all the rest is “of the shelve”. Here is the final result:

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What about performance? My RXV was tuned “fully open” by the Aprilia dealership at 78 BHP and has a secondary transmission of 15/50. A 14-tooth front sprocket is supplied with the bike but I won’t use it. With the 15-tooth sprocket at 100 km/h (60 mph) the engine speed is 6.850 RPM… I swapped the 50T rear sprocket for a 46T and now it’s running “only” 6100 RPM at 100km/h.  The Dakar 450 bikes run 15/48 BTW. Downside of this high performance engine is the poor fuel economy, from a full (12 liter) tank I could only manage to get 135km of range off-road, with 0,6 liter left in the tank. This is 30% more than the 690!!

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This summer I added a Baja Designs KTM EXC 5 liter auxiliary rear fuel tank. With some modifications to the rear frame (cutting off a piece of the sub frame and welding a special made aluminum bracket to hold the tank) I managed to fix it to the rear of the RXV nicely, modifying the plastic of the side panel and rear fender. It’s the same width as the exhaust and very lightweight, so I barely notice it even when it’s full. Now the autonomy is about 185 km which is enough for most Rally’s (>150km)

I simply connected the outlet of the auxiliary tank to the air vent of the primary fuel tank. This way an extra fuel pump is not required, you make sure the extra 5 liters are fully used and you get rid of the extra weight right away! The pump is strong enough to suck a strong enough vacuum to empty the rear tank, no problem: It has worked for 1600km now!

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