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Dynamo Flashing

I think my bike should be negative earth, but I do not know how to check this. The battery has been disconnected for some time now and I cannot remember which terminal was Earth.

As my dynamo is not giving any output, but looks in good condition, I would like to Flash it, but want to flash it the right way round.

I also have a solid state voltage regulator and don't want to wreck this in the flashing process. Will the wiring on the voltage regulator give me a clue?

How do I find out if my bike is positive or negative earth?

Kind regards

Pat

email (option): sacombsashtrees@hotmail.com

Re: Dynamo Flashing

Pat,

I had a similar problem a couple of weeks ago. Take a look at my post:

http://pub37.bravenet.com/forum/static/show.php?usernum=3155626639&frmid=16&msgid=1252431&cmd=show

In the end my problem appeared to be just a dirty commutator but I stripped the dynamo anyway, a relatively straightforward nut and bolt job. The one thing I did first though was to check the field coil resistance, if that was no good then I was going to pit it straight in for refurbishment at a specialist.

Stuart

email (option): stu.gibbins@btinternet.com

Re: Dynamo Flashing

Disconnect the regulator and connect the battery, don't start the engine put the light on and see which way the ampmeter swings. If it swings to discharge the battery is correct if it goes to charge it's the wrong way round.
Check the regulator if its the solid state type it will be marked poss or negative. To polarise the dynamo use a cable from the feed side of the battery once you have found which way round it goes. Use this lead to flash the field coil. flash this to the F side of the dynamo, just a quick flash will do. The other side of the field coil is earthed in the dynamo.
To check dynamo output connect the two terminals on the dynamo together these are marked F and D on the end of the dynamo. Connect this loop to a volt meter the other end of the meter to earth, start the engine and at just above tickover you should see the meter move, raise the revs and the volt meter should show between 10 and 15 volts.
Hope it makes sense.

Tim W

email (option): t.j.walker@btinternet.com

Re: Dynamo Flashing

Hi

Just to be clear, if the solid state regulator is marked positive, then my system is set up positive earth and vice-versa?

Regards

Pat

email (option): sacombsashtrees@hotmail.com

Re: Dynamo Flashing

I would check dynamo output first just in case the polarity is wrong, it could save you a regulator.

Tim W

email (option): t.j.walker@btinternet.com

Re: Dynamo Flashing

The bikes electrics can be set up for either positive or negative earth...If you have a positive earth regulator you have to run it on a system set up to be positive earth.
So, the main earth from your battery to the frame will be connected to the positive terminal and your dynamo will be polarised for positive earth function...
First, check the dynamo output.
To do this disconnect both wires from the end of the dynamo. Now take two pieces of spare cable and and fit them to the dynamo terminals ('D' and 'F').
Join the opposite ends of the wires together. Now start the bike and allow it to idle and put the negative lead of a voltmeter (set to 'direct current') to the joined wires and the positive lead to the dynamo body. Gently increase revs and you should see the voltage rise smoothly to 10 volts plus. If it does so your dynamo is working and is correctly polarised (with the +ve side of the meter to earth)
If you don't get a reading reverse the voltmeter leads so that the negative is to the dynamo body...If you still get nothing the dynamo needs attention.
If you now get a voltage reading you need to repolarise the dynamo.
To do that remove the two test wires from the dynamo and replace only the original 'D' terminal wire. Next take a fully charged battery and connect a wire to each battery terminal.
Now place the positive battery lead to the dynamo body and using the negative lead 'spark' it against the 'F' terminal...It will 'spark' when the bare lead contacts the dynamo 'F' terminal. Use an action similar to striking a match..it is only necessary to spark it once. The dynamo will now be repolarised so check the output again...You should get current with the positive side of the meter to the dynamo body as previously described.
With solid state regulators it is important that everything on the bike is correctly set up BEFORE they are connected to a functioning system...So, having established the dynamo works and that it is correctly polarised the next thing to do is put a fullycharged battery into the system. Use this to check the function of lights ,horn, ammeter etc. Once you are satisfied that the system is functioning correctly then connect the wires to the regulator unit and test to see if the system is charging correctly....Ian

email (option): ian@wright52.plus.com

Re: Dynamo Flashing

Thanks for all your help on this.

I flashed the dynamo and its is working a treat, though it seems to belt out 13 to 14 volts which seems a lot.

If I have a solid state voltage regulator, does this suggest a 12 v system?

All the bulbs are 6v but the rear light is very, very bright (I blew the brake light filament when I tried the brake).

Kind regards

Pat

email (option): sacombsashtrees@hotmail.com

Re: Dynamo Flashing

Sounds as if your reg is set for 12 volts. Some units have a spare wire which when connected with another disconnected gives you 6 volt or there is a white link wire, looks like a small loop that when cut converts the unit to 12 volts if neither then you have a 12 volt reg. Cheapest option change the bulbs to 12 volt ones the horn will work alright on 12 volt the pitch will be higher but for the short time you ever use it it'll be ok.

Re: Dynamo Flashing

Hi Patrick...The dynamo is capable of producing far more than 6 volts..it's why a '12 volt' regulator is possible and why you need a regulator in the first place! If you run the system at 12 volt the engine (and dynamo) need to run faster to 'balance' the system than they would at 6 volt.
Also the wattage rating of the bulbs should not be too high. The overall system load must still be within the capabilities of the dynamo.
People frequently think because they have 12 volts they can run, particularly, a massive headlamp bulb...this is not the case....Ian

email (option): ian@wright52.plus.com

Re: Dynamo Flashing

Hi Ian

So its probably best with 6v and say 10w bulbs?

Kind regards

Pat

email (option): sacombsashtrees@hotmail.com

Re: Dynamo Flashing

My headlamp bulb is I think 24 watt and my tail-light used to be 3 watt but has now been replace with a wonderful low energy consuming LED bulb that gives as much light as a 10 watt bulb.

Henk

email (option): ahum@quicknet.nl

Re: Dynamo Flashing

Hi Patrick..First you have to decide which you want..12volt or 6volt. If you have a regulator that will do either then simply wire it to your chosen configuration. If you have one that will only do one or the other then perhaps your choice has been made for you.
Also there is the question of whether you have the early (45w) output dynamo or the later (60w) dynamo. That will govern the rating of the bulbs you can use at either voltage. At both 6 and 12 volts the tail light will be in the 3-5 watt range. Brake light (if fitted) and horn loads can effectively be ignored as they are intermittent..There are also 'losses in the system' which will vary depending on the quality of the wiring connections (particularly at 6 volt) and the condition of the battery. Not many people realise it but an old and/or badly performing battery can soak up most of the dynamos output...
Finally there is the headlamp bulb..this would be 24 watt at 6 volt on a WD M20, though I have run 30w bulbs on a nicely set up system without problems. At 12volt, on the later dynamo I have run a 35 watt halogen bulb with good results, though on a military bike there is the question of the bulb holder type to consider and what bulbs you can source to fit it....
I find 6 volt lights are quite adequate...particularly if the headlamp reflector has been resilvered (this makes a huge difference) and the focal length of the pre pre focus WD light is correctly set up...
Ultimately though, the arrival of LED clusters for the headlamp will be the thing that really makes a difference...I'm not sure of the current developements there....Ian

email (option): ian@wright52.plus.com

Re: Dynamo Flashing

Thanks Ian.

Unfortunately, two steps forward, one step back.

My dynamo, now flashed is belting out charge. Unfortunately, it seems not to be going to the battery (though the battery is past its best).

Will fit a new battery first, then seek advice re checking the voltage regulator.

Kind regards

Pat

email (option): sacombsashtrees@hotmail.com

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