850 Mk.111 won't run with lights on

Previously wrote:

I have just had a most frustrating ride back from Solent branch meeting, in the dark with only sidelights.

The bike ran fine with headlight on all the way there, 20miles, but was a little difficult to start later.

The bike will start and idle and ride, but spits back when accelerating with any lights on. When headlight is operated it just dies, spits bangs and pops, till the headlight is turned off.

I have just checked the battery and there is at least 10volts in it and the lights and horn work fine on their own. None of the components zenners, rectifyer, battery were hot. Its a new battery as the last one didnt survive the winter. The only non standard thing is Boyer ignition which has been on it for years. I know Boyers need all the power they can get, but I dont understand why after about 30miles it should start playing up ?? Is the alternator at fault ? I am not going to charge the battery now, to see what happens in the morning, if it runs Ok then, it must be something to do with getting hot. Oh how I hate electrics...........

Any help appreciated, thanks

If your battery has 10Volts then it is flat. That is why use of headlights causes problems, you are lucky it runs at all with a battery that is that flat. Waiting will not restore the charge.

Charge the battery with a decent battery charger (Optomate type chargers will not bring a battery back when flat) say at 2 amps (9Ahr battery wants 6 hrs if totally flat) then start and run bike. It should be fine and have at least 100 miles in the battery (assuming that it is not charging) without lights. If using lights then you might get 30 miles.

The fact that the battery is new does not stop it being flat within 50 miles or so if use is heavy (ie lights on) if not charging.

Now the Boyer ignition is very Voltage conscious ie it needs 10V or so, this is NOT the same as power. In fact the power requirements for a Boyer ignition are in effect exactly the same as a coil ignition.

From the sound of things here we have a straight forward non charging fault. I do not know what bike it is but start with the rectifier, if you cannot test it then direct replacement. The Zener is normally NOT concerned with charging, it is only concerned with stopping OVERCHARGING. At this stage pull off the top Zener connection if there is any doubt. But remember to replace before you go back on the road. This just leaves the alternator. You can check this with a head lamp bulb. Across the two wires should be a bright light (engine running) A bulb wire to alternator-the other bulb wire to earth-should NOT light the bulb. Then all is well with the alternator.

Hope this helps. Al Osborn.

Previously wrote:

Previously wrote:

I have just had a most frustrating ride back from Solent branch meeting, in the dark with only sidelights.

The bike ran fine with headlight on all the way there, 20miles, but was a little difficult to start later.

The bike will start and idle and ride, but spits back when accelerating with any lights on. When headlight is operated it just dies, spits bangs and pops, till the headlight is turned off.

I have just checked the battery and there is at least 10volts in it and the lights and horn work fine on their own. None of the components zenners, rectifyer, battery were hot. Its a new battery as the last one didnt survive the winter. The only non standard thing is Boyer ignition which has been on it for years. I know Boyers need all the power they can get, but I dont understand why after about 30miles it should start playing up ?? Is the alternator at fault ? I am not going to charge the battery now, to see what happens in the morning, if it runs Ok then, it must be something to do with getting hot. Oh how I hate electrics...........

Any help appreciated, thanks

If your battery has 10Volts then it is flat. That is why use of headlights causes problems, you are lucky it runs at all with a battery that is that flat. Waiting will not restore the charge.

Charge the battery with a decent battery charger (Optomate type chargers will not bring a battery back when flat) say at 2 amps (9Ahr battery wants 6 hrs if totally flat) then start and run bike. It should be fine and have at least 100 miles in the battery (assuming that it is not charging) without lights. If using lights then you might get 30 miles.

The fact that the battery is new does not stop it being flat within 50 miles or so if use is heavy (ie lights on) if not charging.

Now the Boyer ignition is very Voltage conscious ie it needs 10V or so, this is NOT the same as power. In fact the power requirements for a Boyer ignition are in effect exactly the same as a coil ignition.

From the sound of things here we have a straight forward non charging fault. I do not know what bike it is but start with the rectifier, if you cannot test it then direct replacement. The Zener is normally NOT concerned with charging, it is only concerned with stopping OVERCHARGING. At this stage pull off the top Zener connection if there is any doubt. But remember to replace before you go back on the road. This just leaves the alternator. You can check this with a head lamp bulb. Across the two wires should be a bright light (engine running) A bulb wire to alternator-the other bulb wire to earth-should NOT light the bulb. Then all is well with the alternator.

Hope this helps. Al Osborn.

Further-After posting above I see that it is a MKIII-Ho Hum. The charging circuit is quite different on these. There is half a bridge rectifier completed by using the two Zeners so the zeners are critical this time. The alternator test above is valid, but the rectifier/Zener comments are not. I can describe the testing to any one with some modest electrical knowledge. But on here within a few lines it is not possible.

Al Osborn

Hi Hans. Alan is right about the the two zenners having a double operation. They are used for rectification and voltage limitation:

click here

The zenner unit is the Lucas ZD 715 and the rectifier block is the twin diode 2DV406. It sounds as if one half of eitherhas blown or open circuit. Without hunting around too much and pulling wires off, I would recommendthat you simply measure the charging voltage across a fully charged battery that is known to be of good working condition. Either fit a brand new one that is charged or fully charge your one with connections removed from a normal charger giving at least 2 amps. When the electrolyte is fizzing strongly, measure the voltage across the terminals. It should be around 14-14.5 volts. if this voltage is achieved remove the charger and wait for the voltage to drop down to around 12.7 volts or so, then reconnect the bike's wires.

Check again to see if the voltagehas remained close to that as before reconnection, then start the bike with no lights on and run the engine at moderate revs and monitor the battery voltage, after several minutes the voltage should climb steadily back to the same voltage as when fully charged by the battery charger. Then switch on the main headlight and monitor again. the voltage should return once again to the high value, if it doesn't then the charge rate is suspect and not sufficient. further checks can be done by connecting an ammeter in series with the negative lead. DO NOT HOWEVER START THE BIKE ON THE ELECTRICSTARTER AS THE CURRENT WILL BLOW THE METER!!!!!!!!!!! Monitor the charging current, it should show some charge at least with all electrics working (NOT STARTER)

It is possible to do a rough checkon the rectifier with a mutimeter set to restance (OHMS) using the common centre connection as per drawing. One way you get a low reading and reversing the leads (to either sides of the diodes)a low reading.

The zenner requires around 12.75 volts across it to conduct (there are two zenners per package) It could be tested with a freshly fully charged 12v battery and 12v bulb in series. One way the bulb should light and the reverse way, the bulb should not (both zenners). A basic simple battery charger set to 12 volts can be used as the open circuit of these basic types will rise above the 12.75v and give a better source voltage and a better result than using the battery. Avariable power supply is the best equipment though.

If this allseems too much bother (it is quite simple, honestly) do a substitution test one item after the other, but monitoring the charge voltage at the battery will be the best option still to see immediately if things have improved.

Les H

Hi Hans. Alan is right about the the two zenners having a double operation. They are used for rectification and voltage limitation:

Click Here

The zenner unit is the Lucas ZD 715 and the rectifier block is the twin diode 2DV406. It sounds as if one half of eitherhas blown or open circuit. Without hunting around too much and pulling wires off, I would recommendthat you simply measure the charging voltage across a fully charged battery that is known to be of good working condition. Either fit a brand new one that is charged or fully charge your one with connections removed from a normal charger giving at least 2 amps. When the electrolyte is fizzing strongly, measure the voltage across the terminals. It should be around 14-14.5 volts. if this voltage is achieved remove the charger and wait for the voltage to drop down to around 12.7 volts or so, then reconnect the bike's wires.

Check again to see if the voltagehas remained close to that as before reconnection, then start the bike with no lights on and run the engine at moderate revs and monitor the battery voltage, after several minutes the voltage should climb steadily back to the same voltage as when fully charged by the battery charger. Then switch on the main headlight and monitor again. the voltage should return once again to the high value, if it doesn't then the charge rate is suspect and not sufficient. further checks can be done by connecting an ammeter in series with the negative lead. DO NOT HOWEVER START THE BIKE ON THE ELECTRICSTARTER AS THE CURRENT WILL BLOW THE METER!!!!!!!!!!! Monitor the charging current, it should show some charge at least with all electrics working (NOT STARTER)

It is possible to do a rough checkon the rectifier with a mutimeter set to restance (OHMS) using the common centre connection as per drawing. One way you get a low reading and reversing the leads (to either sides of the diodes)a low reading.

The zenner requires around 12.75 volts across it to conduct (there are two zenners per package) It could be tested with a freshly fully charged 12v battery and 12v bulb in series. One way the bulb should light and the reverse way, the bulb should not (both zenners). A basic simple battery charger set to 12 volts can be used as the open circuit of these basic types will rise above the 12.75v and give a better source voltage and a better result than using the battery. Avariable power supply is the best equipment though.

If this allseems too much bother (it is quite simple, honestly) do a substitution test one item after the other, but monitoring the charge voltage at the battery will be the best option still to see immediately if things have improved.

Les H

SORRY about the double entry. the link has not worked but another diagram is availble here on the NOC site:

http://www.nortonownersclub.org/support/technical-support-electrical/lucas-rm23-alternator

Les

PS PLEASE DELETE ONE OF THE ABOVE VERSIONS, THEY ARE BOTH THE SAME....Thanks

Can't help with actual numbers as I don't have the info or hands on, Al Osborn might have though.

Just need to correct an instruction, I have typed wrongly:

"It is possible to do a rough checkon the rectifier with a mutimeter set to restance (OHMS) using the common centre connection as per drawing. One way youSHOULD get a LOW reading and reversing the leads (to either sides of the diodes)YOU SHOULD GET A HIGH reading"

Thanks...Les

PS TO NOC: Thanks for correcting the LINK, and you can delete one version f you wish. Thanks...Les

Previously wrote:

Thanks gents. I will do some tests. Can you just clarify for me that I have the correct rectifier. Its a solid state one with four poles. Two for AC, one earth , one dc feed. In the diagrams it seems that Mk3 dont use an earth, does that make a difference. The markings on nit are a bit faded, but its something like 36MD ....E made in Malta 12/94

Thanks

Hi Hans

What you're describing is a potted bridge rectifier i.e. a square block that internally contains four diodes connected in a diamond. I've looked at the Mk3 handbook and a standard bike uses two discrete diodes and two discrete zener diodes to form the bridge so it sound like yours has been modified, perhaps to use a potted bridge rectifier followed by one zener or some other regulator?

However, interesting as this might be, it could be a red herring as I take it the config you have was working OK for a long time before and has now failed?

Cheers

David

The Boyer will a base certain voltage to operate. As I understand it, the Boyer system is intolerant of low voltage.

Itcouldbe that you have concurrent faults, each of whichexacerbatesthe other.

Let's start with the battery. In jy personal experience, the voltage on the batteryshouldbe at a minimum of about 12.5 volts when the machine is sat there with ignition off. If you thenswitchthe ignition on you can expect it to dip a little maybe to between 12 and 12.5 volts. No more than just under 12 volts though.

When you start it, I would estimate it will charging properly on a 3 phase 180W system anyway, if you get a reading of 13.5 volts or greater at the battery, over about 2 thousand revs.

Turn your lights on and keep the revs at 2 to 2.5 thou, and itshouldstill show 12 to 12.5 volts minimum.

Now ou may still get these readings and the battery may not be holding its charge due to any number of reasons! Howeverat least you will know your generator and rectification circuits are probably OK.

The Boyer: is intolerant of low voltages and the fault you described - which if I understand correctly is basically that it runs moreerraticallythe more electrical load you put on the system - would be explained by a consequent step reduction in voltageavailable to the Boyeras you switch on each different appliance. This would probably cause a misfire as it fails to time correctly orwhateverit doesn't do when it's in a low voltage sulk.

This suggests to me that either yourmachineis not chargingproperlyor the battery isknackeredand needs replacing (see above).

However it is possible that the Boyer is now out of operating tolerance due to ageing - yep it even happens toelectronics!

What I just did to mine, andwoulddo again, is the following:

(a) Check the voltages. You might find it straight away. (low voltages/duff batterywouldaffect the operation of the coils as well I suspect)

(b) As a matter of course if your machine has never been rewired, working from the front to the back of the bike methodically check all earthing points and connectors for corrosion, ensuring a good solid metal to metal connection. If it is dubious change it. Solder if you can.

(c) Changethe battery positive and negative cables if they are old (welding cable is anexcellentgood quality substitute and cables are easy to make up).

(d) Physically inspect your stator, mine wasphysicallydamaged apparently ina coming together with the rotor. Not good at all.

Thingsto check:

Do you know if you still have the coilballastresistor in place, and if your electronic ignition system actually requires it?

It may be worth disconnecting the comparator thingy that is attached to the ignition circuits - never didtrustthings like that.

In the end, electrics are not too bad provided that you are methodical, logical and use good practice. I viewed it as anopportunityto rid my bike of some potential gremlins!

Now I dare say that people who know a lot more about the subject than I do will set me straight on any mistakes I have made, so I suspect a plethora of experiential knowledge will soon be yours!!

Good luck with it

Jack

Previously wrote:

I have just had a most frustrating ride back from Solent branch meeting, in the dark with only sidelights.

The bike ran fine with headlight on all the way there, 20miles, but was a little difficult to start later.

The bike will start and idle and ride, but spits back when accelerating with any lights on. When headlight is operated it just dies, spits bangs and pops, till the headlight is turned off.

I have just checked the battery and there is at least 10volts in it and the lights and horn work fine on their own. None of the components zenners, rectifyer, battery were hot. Its a new battery as the last one didnt survive the winter. The only non standard thing is Boyer ignition which has been on it for years. I know Boyers need all the power they can get, but I dont understand why after about 30miles it should start playing up ?? Is the alternator at fault ? I am not going to charge the battery now, to see what happens in the morning, if it runs Ok then, it must be something to do with getting hot. Oh how I hate electrics...........

Any help appreciated, thanks

Hi Hans,

If I remember correctly, the correct rectifier has 3 terminals, 2 AC feeds from alternator and one DC output - I will check next time I'm in the garage. I had a similar problem a few years back also whilst riding back from a Solent Branch night out. It was traced to a loose connection on the rectifier, which I found by accident when removing the battery to stick on the Optimate.

Hopefully you will have sorted this out by now but if not, get in touch and I will come and have a look.