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!

velcro

And fitted the phone to see how it looks.

gpsfitted

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.

onenewfit

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:

box

On opening I found this.

box2

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.

package

The packaging was superb!

old_new

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.

two

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.

Steering head bearings – 250

A design from the 1950s or before. The Ducati singles, with one exception, use non-caged ball bearings, 24 in the top and 24 in the bottom. As ball bearings wear there is no way that any adjustment can be made to take up this wear, taper roller bearings would be much better. The fact that they are non-caged does not help either as each bearing needs to be individually inserted into the bottom race and then the top race, as soon as one 4.7mm (3/16″) ball escapes the whole lot has to be dismantled again. Many people have found that as they dismantle the top yoke all 24 balls fall out of the bottom bearing and roll around the garage floor. This did not happen to me as I had prepared.

I ordered 100 stainless steel balls from ebay for around £4.50 and am waiting for delivery. The play is quite extensive in the steering at the moment so I thought that it might be a good idea to clean and grease the existing bearings. After removing all of the balls and removing all signs of grease from them I counted – 47 bearings! One had gone, but nothing was on the carpet in my work area and I had heard nothing fall, so assumed that there had only been 47 in there in the first place. This is an area that needs constant maintenance so I assume that in the 50 years if Dinky’s life, they have been looked at before. Some pictures:

dscn0747

Looking down into the steering head with both the top and bottom inner bearing cups fitted.

dscn0748

This shows the stem fitted and the large (standard) gap around the tube.

When the top ball bearings are fitted into this cup with grease to stick them into place then the top cup can be fitted to hold the balls in place. The top yoke would then be fitted with the nut to tighten everything up. It seems that a previous owner had not been a fussy as I am and one ball had escaped without his noticing. The ball had ended up between the bearing cups and the stem resulting in some damage to that stem, as can be seen in the following pictures:

dscn0751

dscn0753

I can only assume that the result would have been very rough steering and that he eventually dismantled it and removed the damaged ball and reassembled the whole lot with 47 balls.

I shall probably drop some weld into this area and refinish it, but it cannot be seen and does not really make the stem weaker, so might leave it.

I think that a taper roller bearing kit might be on the cards for next winter!

Ignition key

The standard ignition key for a 1967 Ducati 250 single is so basic that any bent nail would work to switch the ignition on. If someone wants to steal a bike then they will probably lift the bike into a van, but I am not going to make life easy for them. As I never had the key for Dinky, I used a fuse holder inside the headlight and just inserted a 10 amp fuse to switch the ignition on.

I bought an ignition switch from ebay for the grand sum of £3.50 but at least it has a double sides key and can’t be switched on with a bent nail. The only thing was fitting it. I do not want the do anything to Dinky that is not reversible, that means that she can be returned to a standard bike without any effort in the future. For that reason I cannot just remove the old ignition switch from the headlight shell, enlarge the hole and fit the new switch, as that would damage the shell. The end result was to make an aluminium bracket that fits to the top of one of the front forks. The new switch, with key, is indicated in green in the following photos , the red arrow is the old switch.

ign2 ignsw

The result looks quite neat.

The next job was to fit the headlight for the first time. An LED bulb was fitted into the sidelight position to be sympathetic to the puny charging system on this old bike and will be used as a running light. If I switch the 45 watt headlight on instead of the LED then it will use just about all of the electrical power used by the little bikes generator.  I was surprised to find that the headlight lens is plastic and was just thinking how advanced Ducati were in 1967 to fit plastic lenses, my guru Craig, shattered that illusion and told me that it should be glass.

hlight

It does look rather cute now though.

As most of the major stuff is done for now on Dinky the Ducati, I shall move back to some work on Ronnie the BMW RS with his cafe racer conversion.

Tyres

We went out to lunch today, a 5 course meal with wine and coffee included at €14 a head, and all home cooking. All the bikers who have visited know exactly which restaurant we ate at!

When I got home there was a missed call on the home phone, it was Dafy Moto in Perigueux. I knew exactly why they were phoning, my new tyres had arrived for the 250. I immediately got back into the car and shot into town to collect them, with 2 new tubes and a bottle of 20 weight fork oil.

tyres1

The tyres have a very sporty tread pattern for such old sizes, but I suppose that there must still be a demand for them for some older bikes. The prices can be seen on the labels, but so can the max speed, 150 kmh or less, and this might be a problem as some of the 250 Ducati’s were capable of 170 kmh. I guess I won’t be asking that much of her, if I need some speed then I’ll take the 848 out.

The front tyre is now fitted to the very nice alloy front rim. Fitting the tyre took nowhere near as long as cleaning the rim up. Sometime in the past someone has used steel tyre levers and marked the rim, but that is all now polished out.

Tomorrow will be the back tyre and then a fork oil change. I will keep the old tyres for a laugh as they have been fitted to the bike for at least 24 years and still hold air!