Ducati Supersport horn

When I bought my first new bike back in 1977 at the age of 18, I had my fathers words in my mind, “Make sure that every bike that you own has good lights and a good horn”. That BMW R75/7 had both.

Here we are 40 years later and I have just bought the new Ducati Supersport 939. This bike comes with some decent lighting as standard and has the LED strip for daytime conspicuity, nothing needed there then. The horn on the other hand was like Mickey Mouse farting! It could not be heard over the sound of the engine on tickover. Bikers who have visited this area will know that there is one huge danger on the roads in this part of France – Belgian car drivers. A good horn stops them in their tracks.

The horn of choice was the DENALI Soundbomb Split. I went for the split as there is not much room on the Supersport and with the split I could use both sides of the bike. Here is the kit:

The part on the left is the dual tone air trumpet, the fitted aluminium bracket is my construction – more of that later, centre is the compressor and on the right is the air hose to connect the two. The kit also came with a relay which I threw away and fitted a better quality one.

The trumpet was fitted under the left fairing fillet panel with the home made bracket.

These are the two bolts that hold the fillet panel on, remove them and pull the panel rearwards and it comes off.

The following two pictures show the bracket that I made from aluminium to hold the trumpet. This is bolted with a rubber packer so that it is insulated for vibration from the bracket.

The bracket holds the trumpet out of sight below the fillet panel, and attaches to the top radiator mount and the bolt that holds the existing horn in place. Here it is in position.

The trumpet must have some clearance around it so that it when it is in operation it is not able to touch anything. The original horn is left in place and left connected, it can be seen in front (right in picture) of the bracket leg.

The compressor was fitted on the other side of the bike, also on a bracket bolted to the top radiator mount. The radiator expansion tank hose is a hindrance to using an allen key on this bolt, so a hex head bolt was fitted.

The relay was operated by piggyback wires from the original horn. The reason for keeping that horn is that the electrical system will not operate the Soundbomb alone as it draws too much power and the bike thinks that there is something wrong. The compressor is wired to the battery through the relay and a 25 amp fuse. Note the carbon fibre mounting bracket on this side. I have to thank my aircraft career for the ability to make brackets!

The horn button on the bike is now a thing to be wary of, I would not use it to say hello to someone on the side of the road as the ground shakes when it is pressed. Watch out Belgian drivers!

A small experiment

I say experiment because I have known of these items for years and at last decided to try them. They are Grip Puppies. These things fit over the standard grips in a bike and do a number of things, they make the grips thicker and more comfortable and they add padding so that vibrations are damped when wearing thin summer gloves.

I bought them from ebay LINK, and they were here within a few days. They take 10 minutes to fit over the existing grips with a little soap and water and then are left to dry.

I went out for a ride with them fitted and was instantly impressed with the feel of them.

My wife likes them too so another set will be ordered for her ST2.

Exhaust valve.

It seems that many new bikes are fitted with a flapper valve in the exhaust these days, Ducati being one. If you look back through the posts you will find that I took the exhaust valve motor out of my 848 and fitted a little box to fool the ECU into thinking that it was still fitted. Well I have another little box the same.

This picture shows the oil filter from a previous post but the exhaust valve gubbins is in the same area. The valve itself is under the triangular cover to the rear of the green circle, it is held on with three bolts. Just under the front of the green circle, the cable that runs to the motor, which is in the lower front of the fairing. is just showing, 

First thing that I did was to take a short video of the motor with the bike running to see when it was closing the valve.

This actually proves nothing apart from the fact that it is working. In my  view anything that is making a restriction in an exhaust system for no known reason is a waste of time, and does nothing for efficiency.

The motor and cable has been totally removed along with the brackets. This saves a bit of weight, not that I’ll ever notice while riding, and gets rid of that ugly cable hanging down. The valve itself is still in the exhaust but is wirelocked in the open position.

Time will tell if the modification has any effect on the way the bike runs, or on economy. It is very easy to reinstall everything if needed.

All that I need now is a spare exhaust box to see how easy it will be to cut open, remove the catalytic converter, and weld closed again. That is one modification that I know from experience makes the machine more economical and boosts mid range torque.


Ducati 250 single ignition

I have read that the 250 and 350 Ducati singles are very fussy about ignition timing. They need to have about 36 degrees of advance when running at higher engine revs, but about 5 degrees static. The reason that the spark fires so far ahead of TDC is so that the fuel mixture has time to expand at the correct point in the engine, where the maximum pressure from the explosion will do the most work. At low speed it needs to be nearer TDC to allow the engine to be kick started.

The system is an old fashioned points and condenser with a centrifugal advance mechanism that should give about 31 degrees of range. There are no timing marks on these engines so a bit of work is involved in setting the timing with the engine static. There are some good explanations of how to do this on the net, notably this one http://www.liebold.com/timing/timing.htm and I thank the author for sharing it.

I found that after setting the timing correctly, the bike would start but the performance was dreadful, as if the timing was wrong, so I adjusted it by ear and got it running better. It still was not correct. The little bike could only achieve 95 kmh (55 mph). Further investigation was needed.

I took the two bolts out of the points cover and examined the parts behind with a bright light and noticed that the wire on the condenser was attached with a single strand. I removed the points plate to resolder the wire.

The picture above shows the points and advance mechanism housing with everything removed.

And this picture shows the wire that should be attached to the condenser.

Now I have been soldering all of my life, off and on, and it is not difficult to do, but this job was a failure. There was no way that I could get solder to stick to the stub on the end of the condenser, so a new condenser with wire was required.

Behind the points plate is the advance mechanism, it is removed by taking out the small bolt in the middle of the cam. So out it came. I noticed immediately that something was not right with it. There was too much play in the thing. The springs are not stretched but are loose. This means that in the static position it could be either 5 degrees or about 12 to 15 degrees of advance without the engine even running. This could mean that the bike only had a total advance range of about 20 degrees.

The bottom picture shows how there should be no gap (red arrow) but the spring appears loose (blue arrow). This is the position that you would time it static.

The upper picture shows that the gap in the weights (red arrow) would be about 7 or 8 degrees different still with the engine static. The springs (blue arrow) are now touching the post but have no tension on them.

The best solution to this mess is, in my opinion, a nice electronic ignition system that does away with points and condenser, and replaces the advance mechanism with an electronic version. That system has been ordered and will be the subject of the next blog post.

Phone/GPS mount for the 250.

Readers may remember that the only time that I have ridden the 250 M3 was up and down the lanes around here. One thing that I noticed, apart from the gears being upside down, was that the speedometer was unreadable as the needle jumps all over the place. As this is going to be a bike that will be used, it is important to me to know how fast (or slow) I am riding. The solution is a small smartphone running a GPS speedo application. It just so happens that the phone that I own is small, I bought it so that I can use it on the 848, and is ideal for the solution.

First thing to do is buy a 4cm wide piece of aluminium extrusion. It is not super strength aluminium , but it only needs to hold a phone. I cut my bit 14.5 cm long and drilled a 26 mm hole in one end. I then put a slight bend in the bracket so that it should not get too many reflections on the phone, this is the result:

bracket bracket2

Okay it doesn’t look like aluminium extrusion, that is because I polished it with Micromesh so that it matches the alloy top yoke on the bike.

After fitting I stuck a piece of strong self stick velcro to the bracket, and then wondered why I had polished it!


And fitted the phone to see how it looks.


It will work just fine. It is a very functional mod that can be removed in seconds so does not alter the fabric of the bike at all.

My helmet, a Schuberth C3 Pro, is fitted with a Sena 10u intercom system so that I can communicate with my wife on her bike. The little phone can also be used in GPS mode with the instructions being bluetoothed to me.

Front fork top plug.

The nice thing about the 50 year old bike is that there is loads of aluminium to polish. I love aluminium, probably due to a life spent repairing aircraft made from the stuff. But aluminium has its place and that is not everywhere.

The 31mm fork tubes on the bike are made of steel, as one would expect, as they need to be strong. The top yoke is made of an aluminium alloy casting and that is also strong enough for the forces involved on that item. But the plugs that attach the two parts together are also aluminium and they have a screw thread that screws into the steel fork tops, never a good idea. This is where they are fitted. In this picture the one on the right is the new one, more later.


These pictures show the problems with aluminium alloy fork plugs.

two_old oldtop

As can be seen, the 12mm allen key holes have been damaged by a previous owner who probably needed to take them out but did not possess a 12mm allen key, but even worse the threads have been ripped off the alloy by the steel threads of the forks. I have no idea if this is due to over tightening or just wear and tear over the last 50 years. The reason that the top four threads are not damaged is that these do not screw into the fork tubes, but sit inside the top yokes.

The answer is a set of steel plugs. This arrived today in the post:


On opening I found this.


Which was kind of amusing. The manufacturer of these stainless steel fork plugs obviously has a fantastic quality control system which involves the local medical laboratory or he has reused a box, made me laugh anyway.


The packaging was superb!


This is the old and the new on my desk with the correct removal tool above them. This picture illustrates the lack of thread left on the old one. If you now go back to the first picture you will see that a new stainless steel one is fitted to the right hand side and the old alloy one on the left. They are both steel now.

The threads on the new ones were slightly rough on the skin, nothing to worry about, but being a perfectionist, I rubbed them over with some 4,000 grade micromesh just to polish the edges slightly before a quick wash off with degreasant, refitting of the o-ring and fitting to the bike. This procedure was overkill as they can be used out of the box.

The new plugs were bought over the internet from www.eurojamb.com and I will let you browse their website to find the price, but be assured that for the quality they are well worth that price. Joe at eurojamb is also a star, he is quite willing to answer emails promptly, even ones from people like me who try to avoid ordering anything from the US. Thanks Joe.


Electrics – charging system

The Ducati 250 has does not have the correct regulator/rectifier fitted. The original probably gave up at some time over the last 50 years of its life and a previous owner fitted what looks like a British bike system that might even be older than the bike itself! The two parts are separate and are shown in the next picture by two green arrows.

oneThe other thing that can be seen from the picture above is the amateur wiring using any old bits of car and household cable with Lucar connectors crimped onto them. That will all need to be changed to look more original. While this old system was fitted I checked the voltages, Battery was 12.83 volts without engine running, I have a feeling that my voltmeter is over reading by about 0.3 volts. With the engine running it went up to 15.4 volts, so it is charging the battery, but even if that is 15.1 after deducting the assumed voltmeter error, it is too high for my liking. with the puny 35 watt headlight on it dropped to 13.7 volts, indicating that the 40 watt alternator is getting near its limit.


I bought this regulator/rectifier from ebay for the grand sum of £17 from China. It claims to be a Mosfet RR, but I am not so sure for that sort of money. Mosfet is a new type of RR that is bang up to date, it generates less heat and is supposed to be more efficient. Read about it on Google if you are are an electronics buff. The fact that it has three alternator inputs (I have marked them in yellow) say that it can be used on a more modern 3 phase generator, but in this single phase application it is fine to use just two inputs as that is all that comes from the generator. The other two connectors are for battery positive and earth.

threeThis is the new one fitted. There is plenty of space under the seat so it will get plenty of cool air.

The voltages are a bit different, the battery was still around 12.8 volts, but the running was now at a much more controlled 14.4 to 14.5 volts. Switching the light on still dragged that down to 13.7, so the battery is still charging.

On an old bike with no electronics the original 15+ volts would probably do little harm. It might shorten the life of the battery a bit, but you may never notice. I intend to fit an electronic ignition system made by Elektronik Sachse in Germany, but having spoken to the company it seems that there have been a couple of failures of their electronic boxes (I understand that the rate is miniscule, about 2 to 3%), and that may be due to the users bikes charging system producing an over voltage. There website is CLICK HERE.

This regulator will also fit my wife’s Ducati ST2, a bike that is known for weak electrics and a bike that is also fitted as standard with a single phase generator.