VUN Clutch Cable Route

I recently needed to replace a frayed clutch cable on my VUN. After fitting the replacement cable along the exact same route as the old one I realized something was not right. The cable was simply too tight and pulled the clutch in as I turned the steering.

After some head scratching I realized that the new cable was 10cm shorter than the one I needed to replace. Timo, a technician at CR&S, explained that the new cable is correct and has been modified from the original item. Fitting the shorter cable requires a different cable route. The images below were kindly sent by Timo to demonstrate how to fit the new (shorter) cable.

If your clutch cable has an outer length of 81cm and inner length of 93cm then you have one of the new (shorter)  cables that should be fitted as shown above.

My VUN with original (longer) clutch cable. If your cable has an outer length of 91cm and inner length of 104cm then you still have one of the original longer cables.

As you can see above, the older cable route tends to obscure the instrument panel, whereas the new clutch cable route does not. My guess is that this is the reason for the modified cable/cable route.

Haynes BMW F650 Singles

If you didn't already know it, the engine used to propel the VUN is the same one used by BMW for its range of F650 singles. Specifically, it is the twin-spark plug version of the engine used by F650 models between 1994 and 2000. The original BMW engines were fueled by twin BST constant velocity carburetors whereas the VUN is fitted with Dell'Orto electronic fuel injection.

This is one example of the sort of thing you can learn by reading the Haynes Service and Repair Manual for BMW F650 Singles.

I've always found Haynes workshop manuals to be excellently written. The instructions are good enough for even an experienced fool like me to follow.

The manual is split into logical sections: Maintenance, Repairs and Overhaul, and Reference. Each section is broken down into chapters, for example under Repairs and Overhaul there are chapters on: Engine, Clutch and Transmission; Frame and Suspension; Electrical System, etc.

VUN owners will be primarily interested in the engine, clutch, transmission and ignition system chapters. The overhaul chapters explain each major operation (e.g. cylinder head overhaul) in detail breaking it down into:

• Overview,
• Special tools needed,
• Removal,
  
• Disassembly,
• Inspection,
• Reassembly,
• Installation.

Detailed photographs and diagrams are provided all the way with step by step instructions.

The reference section at the back of the manual provides valuable general technical information on such diverse things as: reading spark plugs, fastener types, thread repair, fault finding, a technical terms glossary and so on. This section is fairly comprehensive and is very useful to non-professional hacks like me.

My VUN's warranty still has a long way to go so I am unlikely to need to overhaul my engine anytime soon. However, it would have been useful to have this manual around the day I decided to remove the oil filter cover to see what was behind it. I could have avoided spending 40 minutes cleaning up spilled oil that day (what was I thinking?).

My intention in buying this book was mainly to learn something about the internals of this engine and, in the future, how it might be modified to provide more power and less rotating mass.

I ordered my copy over the internet (how else?) from Motor Books in the UK. Their website was well setup, their price was competitive and ordering my book was straightforward. The book was well packaged and arrived in perfect condition. Delivery took nearly 3-weeks from date of order, but I should have expected that since I placed the order during a protracted postal workers strike in the UK.

Lightweight Battery (2 of 2)

(part two of a two part article)

Fitting the Speedcell Battery

Remove the seat: Unlock the the rear seat pad, remove the two bolts that hold on the seat, then remove the seat. This gives you access to the rear bolts that fix the gas tank. Remove the seat by sliding it back and up. Check the owners manual for more information and diagrams on removing the seat.

Be careful not to damage the rubber grommet which holds up the tail light assembly. Put a dab of Vaseline (petroleum jelly) or suitable grease on the inside of this grommet. This will help you replace the seat without damaging the grommet. When replacing the seat I also like to put a drop of Loctite on the bolts holding it down. These bolts have a tendency to come undone due to vibration.

Click to enlarge

Undo the gas tank: Remove the four bolts that hold down the gas tank (two front and two rear). Now lift up the front of the tank to give you access to the battery. Be careful not to pull the fuel lines and fuel pump wiring harness too tight. Support the tank in this position with a suitable piece of wood. If you have something the right size it can be slotted under the tank in such a way as to support it in a stable way.

The alternative is to disconnect the fuel line (undo the bayonet connection), remove the fuel breather hose, disconnect the wiring harness to the fuel pump and then completely remove the tank. I did not do this because I had trouble getting the fuel line disconnected and I did not want to damage the bayonet connector. This is probably just me not knowing how to do it properly.

I have a philosophy related to motorcycle maintenance. If it requires more force that you'd expect to undo a part then you are doing it the wrong way. Stop and think again. This rule only applies to modern motorcycles :-).

Remove the old battery: Black = negative, red = positive. Always undo the negative battery terminal first! This is because the negative terminal is connected to the metal parts of your motorcycle, making them all negative (also known as "earth"). If you undo the positive terminal before removing the earth, then you could short-circuit the battery by touching any metal part of the motorcycle with your metal spanner. You do not want to do this! Once the negative terminal is undone, it is safe to put a spanner (or screwdriver) on the positive terminal.

Looking down. Note all the extra space. Click to enlarge.

Fit the Speedcell battery: Do not remove the plastic cover on the new battery's negative cable just yet. This is to prevent the two leads coming together and shorting the battery (bad).

The new battery fits snugly into the existing battery box. I fitted a strip of rubber adhesive padding between the metal bracket at the front of the battery box and the new battery (see right-most red circle in image above). This makes the fit tighter and prevents the battery from rubbing directly against metal.

I used two fairly heavy duty cable ties to secure the new battery. One at each end of the battery (see photo). These simply go under the metal battery box and over the new battery. I wrapped a smaller cable tie around these two to stop them from being able to slip apart (this is not shown in the photo). You might want to wrap a third cable tie around the middle of the battery for extra security.

Remove the black cable that used to connect to the negative terminal of the old battery. The new battery's negative lead will bolt directly to where the other end of this cable connects to the frame (top red circle in the image above). But don't connect the negative battery lead yet as this will earth the whole bike. Use the rubber protective caps from either end of this old cable to fit over the two red and black (positive and negative) leads of the new battery.

Now bolt the battery's positive (red) lead to the two cables that used to connect to the old battery's positive terminal. I used the old battery's terminal bolt for this. Now cover the exposed metal where these wires are bolted together with the black rubber protective cups. I used a small cable tie to secure the positive lead to one of the cable ties that hold down the battery. Position the lead so that the join is not able to contact with any metal part of your VUN. See bottom red circle in the image above.

Now it is safe to remove the protective plastic cover on the Speedcell's negative (black) lead. Bold this lead into the position where the old negative cable used to connect to the frame and place the protective black cap over it (see top red circle above).

Test that the battery is securely positioned and that the positive terminal is not exposed to any metal parts of your motorcycle.

Now you can replace the tank and seat.

Testing the new battery

My Speedcell battery arrived in the mail fully charged. If your's is not charged then you will need to do this first. With the new battery fitted my VUN started right away. I have been using the VUN fitted with the new battery for a few weeks now and I can say that it works fantastically well. I have had absolutely no problems and the bike always starts strongly.

It is probably an illusion due to the fact that I just got back from a long trip with a heavy tank bag attached, but the VUN does feel lighter. Whether or not I can really 'feel' the difference, the VUN is 3KG lighter than before. I am very happy with this change and I can't wait to take the next steps towards a lighter VUN.

Lightweight Battery (1 of 2)

(part one of a two part article)

After years of riding bikes that are complicated and heavy I have become a little bit obsessed with weight, motorcycle weight that is. Generally, having low weight means: better cornering, better braking, better acceleration and easier to ride. Also known as... more fun.

This is why I chose a VUN in the first place. The VUN weighs around 135kg (dry) if fitted with Marvic Mag wheels. This is light, but it could be lighter. I have set a goal to get my VUN down to around 120KG (dry). I'll be documenting each step I take to reach this goal here on this Blog.

Choosing a Lighter Battery

The VUN's standard battery weighs about 3.7KG. How much of that can be saved by using modern lightweight battery technology? I did some research and found a bunch of solutions ranging from regular lead-acid batteries with carbon fiber casing to lithium ION battery packs. Some people recommend just getting a smaller (and thus lighter) lead-acid battery.

• Carbon fiber cased lead-acid batteries seem like a waste of money. The weight in any lead-acid battery is: 1) the lead and 2) the acid. Paying money to make the plastic casing lighter does not make sense.
• From what I have read, 'regular' Lithium ION batteries are not suitable. They would require special charging circuits and seem to be unreliable (even potentially hazardous). I would keep away from these.
• Do not fit a smaller (less powerful) lead-acid battery to your VUN. See below to read why.
  

Lithium Ferrous Technology

After some research I chose a 4.6 amp hour Speedcell Lithium Ferrous battery. Here are the specs:

- Pulse discharge @ 10 seconds = 240 Amps
- Continuous discharge (MAX) = 140 Amps
- Cycle Life = 1,000 cycles

- Dimensions = 10.5cm (L) x 5cm (W) / 4.13" (L) x 1.96" (W)
- Rating = 4.6Ah
- Weight = 766.57g / 1.69lbs!

Yep, that's 766 grams vs. the standard battery's weight of 3.7KG. A weight saving of 3KG.

Speedcell battery - side view. Very light and small too.

Important: VUN Starting Requirements!

I could have chosen an even lighter Speedcell battery and saved another 300 grams, but this would have compromised the ability to quickly and easily start my VUN. Never fit a less powerful battery to your VUN! The VUN requires a strong battery for no-fuss starting.

A big (650cc) single is hard to start. Singles also have a tendancy to "kick back". This is what happens during starting when the fuel ignites as the piston is still rising up in its compression stroke. If this happens then it can reverse the direction of rotation of your engine for a short period. This is not very good for your starter motor gears.

The VUN electronically retards the ignition timing for 3-seconds during starting. This prevents kick-back. However, if your engine does not start within 3-seconds, then you run the risk of a kick-back and potential damage to the gears that engage your starter motor. This is why you need a strong battery. A strong battery will always start your bike quickly. A battery that is not so strong will not.

The moral of this story: After 3-seconds take your finger off the starter button, no matter what... and if your battery is getting weak, buy a new one.

More About the Speedcell

Unlike a lead-acid battery, Motowheels.com claim that the Speedcell will only drain by about 2% when left off charge. This means that you never need to run a trickle-charger to keep it topped up. Its operating temperature is from -50 C to 49 C. Battery life should be at least equal or greater than that of a lead-acid battery (depending on how well you look after your lead-acid battery). The battery is designed to work with your standard charging system.

Lithium Ferrous cells are currently the battery of choice in electric vehicle applications.

Buying the Battery

I bought my battery over the web from Motowheels. Their price is $250, for the 4.6Ah SBK model I chose. This is much more than the cost of a standard battery obviously, but it is pretty good value in terms of $/KG of weight savings. Think about the cost of a carbon fibre seat for your VUN. The seat costs  €803 (plus tax) for a savings of about 1kg.

The Motowheels website was well set up and ordering the battery was easy. The battery arrived after about 2-weeks. It was well packaged and arrived in perfect condition and 100% charged! I guess the "no-loss" claim is true. It also weighed slightly less than advertised: 650 grams against 766 grams so I was happy about that.

What I was not happy about was the shipping costs of $145. This was 60% of the cost of the battery and seems excessive. I knew in advance what the shipping costs were but the Motowheels web site actually said that this would be the "maximum" cost and they would refund any difference between this and the actual cost. Instead, when I checked my credit card, I found that the cost had increased by an additional $35 (total shipping $180), so I feel like I got ripped-off. Maybe this is one of the disadvantages of living in the Czech Republic.

If you are based in Europe then I would try to find a local European source and avoid all this shipping rip-off nonsense. Durbahn, is a German manufacturer and reseller of performance motorcycle parts. They offer a similar product in their English-language web-shop. The 4.6 Amp-Hour model costs €176.31 (including tax) which is almost the same cost as the Speedcell at today's exchange rate. I have never used Durbahn or their products so I can't vouch for them, but it looks like you will get the same product without the high shipping charges if you are based in Europe.

(in part two: fitting and testing the Speedcell battery)

VUN Power Upgrade #1

The VUN's light weight means that it can accelerate quickly to 100km/h despite putting out only 54bhp in standard trim. But there are a few things about the standard VUN's power delivery that could be improved. I'll go through them...

• It is definitely sluggish in the mid-range. The engine doesn't really pull until you get into the power band. In the mid-range you can feel it is gasping for air (you can hear this too).
  
• The rev limit is about 7,500 RMP. Because of the first problem, if you want to ride hard, you will be always trying to keep the engine RPM high to stay in the power band. I found myself constantly hitting the rev limiter when pulling hard out of slow corners in 1st or 2nd gears. When you do this it feels like you just threw out an anchor, there is just not enough range.
  
• There is a slightly annoying splutter at very low throttle openings at any RPM (except idle). Actually, I didn't really mind this too much. It's fairly easy to ride around the problem by selecting a higher gear or by slipping the clutch at the right moment.

Air Filter Upgrade

I asked VUN dealer for Bologna (Italy), Franco Cavina, what simple things he would suggest to improve the power. He said the first thing to do is exchange the standard paper air filters with free flowing metal gauze filters. When you do this, a change to the fuel-injection map is also needed to keep optimum the air-fuel mixture.

Even though my paper filters were still in good condition I decided that, when I was in Milano, I would ask the guys in CR&S to make this modification as the mid-range flat spot was really bothering me.

A CR&S technician fits high-flow air filters to my VUN. Roberto Crepaldi is lurking in the background.

The VUN has two ducts either side of the seat that channel air into a still air box in the ducktail. From there the air is fed through two rectangular cartridge filters to the injector body intake duct. Changing air filters is as simple as removing the seat (two screws), then swapping out the air filters.

Select high quality, high-flow metal gauze cartridges. These cost more than the paper cartridges but it is worth it and they last longer since they can be washed whenever they get clogged up.

Dump those Catalytic Converters

Two catalytic converters are mounted inside small bulges in the header pipes, one on each side. I don't know how you feel about it but I resent catalytic converters. If you live in a country where you can still get away with not having them, then I suggest getting rid of them.

I don't know if it is possible to take off the headers and hook them out. In my case, I swapped the original header pipes with some "track-only" pipes which don't contain catalytic converters.

Software Upgrade

Changing the filters and removing the catalytic converters requires a new fuel-map to ensure the correct air-fuel mixture is maintained. I had this done at CR&S. It was pretty simple. They just plug a laptop into the communication port on the right side under the fuel tank and select an appropriate fuel map for the modifications.

I asked if they would also raise the rev limiter by 500 RPM. I figured that would be enough to stop me from hitting the rev limiter in 1st and 2nd gears under hard acceleration. They said it would be OK, so my rev limit has gone up from 7,500 RPM to a more respectable 8,000 RPM.

Testing the Changes

I would get these changes done at your friendly local VUN dealer. They should have the software, fuel maps and expertise to do this properly. Without changing the fuel map for the injection system the air-filter change will probably make your VUN run worse.

This all took just a couple of hours, then it was time to take the VUN for a test ride... WOW! I expected an improvement, but this was much better than I ever expected!

Someone once told me that it is hard to notice any power increase unless it's more than about 10%. I don't know if that is true but I could feel a definite power boost across the entire RPM range and at every throttle opening. The mid-range flat spot was completely gone and the peak power was definitely boosted. Even the splutter at low throttle openings has disappeared! It feels like my VUN finally has the power delivery that it deserves.

I would recommend these changes to every VUN owner. It is simple and cheap and it makes your VUN much more fun to ride.

I was able to make one fairly credible measure of the peak power increase. On my ride down to Italy I measured my top speed at about 182 km/h with a big tank bag and backpack (without the luggage I normally get about 192 km/h). Top speed is determined by the point where wind resistance and turbulence overcomes the power delivered by your engine. On the way home, with the same tank bag and backpack, I could reach over 192 km/h. That's a simple measure but it represents a pretty significant improvement.

The real payoff can be felt on those twisty, switchback, mountain passes... the "mistostretto". Pulling out of corners is smoother and more responsive. The engine now gives you more flexibility and there is no slamming into that rev limit.

Appropriate Warnings

Raising the maximum RPM might void your waranty. This is probably up to the discretion of your dealer (or CR&S). Get this done by your dealer and make sure they are OK about it. Definitely don't do this until after your engine is properly run-in. I changed mine after about 5000 km.