DT50MX Ignition fault

[Ardy]

I have just finished restoring a 1982 dt50mx, the problem is I can't get no spark, I've changed the Ignition coil, points, condensor & plug, Iv'e had the source coil rewound, carried out various cont checks, still nothing.

The inline diode that goes between the coil and stator has also been replaced. Iv'e conected a 24v test light to to check the output from the stator it seems to be producing current but I think its not enough to generate a spark.

I've also tried a stator from a friend bike that I know works, still no spark.

The ignition switch and the stop switch have been checked for any short circuits, Iv'e even tried with them dissconnected.

Iv'e run a seperate earth lead direct from the battery to the engine casings, incase of earthing problems from powder coating.

All the multi plugs have been checked for corrosion, Iv'e dissconected all the lighting harnesses incase any of them have gone to ground, the list is endless.

Any ideas?

Regards

Ardy.

[wild foamy]

have you done the standard things like check plug cap and switch resistance?

also things like points/CDI?

[Ardy]

have you done the standard things like check plug cap and switch resistance?

also things like points/CDI?

Hi Yes, the points, plug condensor and cap have been replaced, both the ignition switch & the handlebar stop switch have been tested too.

I have noticed since my last post, that disconnecting the stator plug from the main loom and connecting a test light the generator will create power, plug it back in and try nothing.

I know that the coil has to be earthed to the frame but in doing this, the generator will cease to create any power at all.

Thanks for the reply

Ardy

[Cynic]

Hi Yes, the points, plug condensor and cap have been replaced, both the ignition switch & the handlebar stop switch have been tested too.

I have noticed since my last post, that disconnecting the stator plug from the main loom and connecting a test light the generator will create power, plug it back in and try nothing.

I know that the coil has to be earthed to the frame but in doing this, the generator will cease to create any power at all.

Thanks for the reply

Ardy

Sounds to me like the points are not opperating as they should. With the ig on if you manually open the points you should see a spark at the plug, and to a lesser extent at the points as well.

Take out the plug, or use a spare and have it set so you can see any spark. Then pull the connector plug to the stator with the ig on, this should cause a spark if i'm on the right track.

What you are seeing from the generator is potential difference (voltage) not power of any discription, this will dissapate in the coil readily enough. Its when that potential is shut OFF that the magic happens in the coil and the spark is created.

[JimR]

Hi Yes, the points, plug condensor and cap have been replaced, both the ignition switch & the handlebar stop switch have been tested too.

I have noticed since my last post, that disconnecting the stator plug from the main loom and connecting a test light the generator will create power, plug it back in and try nothing.

I know that the coil has to be earthed to the frame but in doing this, the generator will cease to create any power at all.

Thanks for the reply

Ardy

Hi Ardy,

if you have fitted new points have you cleared the covering from them ( a small mag/warding file will do) an set the timming to 1.8mm btdc for a reason these bikes will not produce a spark if the ign timming is to far out, You cannot just gap the points you need the points to open at 1.8mm btdc +- 10%. Gapping the points to 12 thou at tdc will not insure a spark.

Don't forget this motor does not need a battery to run so any ref to needing one to produce a spark can be ignored.

Which wire from the stator plug (Black,Yellow,Green/Red or sky blue) did you get power from ? For the ign you would only need to look at the black (or black/white depending on age) and for sure by a simple disconnect of the plug from the loom could give a 'spike' from the ign circut if the condensor is charged and the points in the correct position.

When you earth the HT coil how are you doing this ? If the bike is later Yamaha changed the ign to black/white rather than black in order to stop people connecting the ign straight to earth (no spark from that ! D) )

Regards Jim

[Ardy]

Hi Ardy,

if you have fitted new points have you cleared the covering from them ( a small mag/warding file will do) an set the timming to 1.8mm btdc for a reason these bikes will not produce a spark if the ign timming is to far out, You cannot just gap the points you need the points to open at 1.8mm btdc +- 10%. Gapping the points to 12 thou at tdc will not insure a spark.

Don't forget this motor does not need a battery to run so any ref to needing one to produce a spark can be ignored.

Which wire from the stator plug (Black,Yellow,Green/Red or sky blue) did you get power from ? For the ign you would only need to look at the black (or black/white depending on age) and for sure by a simple disconnect of the plug from the loom could give a 'spike' from the ign circut if the condensor is charged and the points in the correct position.

When you earth the HT coil how are you doing this ? If the bike is later Yamaha changed the ign to black/white rather than black in order to stop people connecting the ign straight to earth (no spark from that ! D) )

Regards Jim

[Ardy]

Hi All

Thanks for the info, I checked and double checked the timming and the points start to open around 1.8mm btdc, and the points were cleaned when fitted.

The main earth from the battery, (black wire) is fixed to one of the igntion coil securing bolts, and the coil plugs into a black and white wire its this wire from the stator that I'm getting voltage from by simply kicking it over.

Whats so odd about this fault is that I've taken a perfectly good stator and flywheel from a friends bike, fitted it to mine and nothing happens.

I'm well aware that these engines don't rely on battery voltage for ignition, so It should be so simple. To my way of thinking providing that I don't have the points going to permant earth, a spark should occur when they start to open. if the points are going to permanent ground it begs the question why?. The wiring loom is in excellent condition no sign of it ever being opened and you certainly cant get the plugs wrong.

I should add that I have dissconected the harness completly and isolated everthing else, I've also tried using single wire from the stator to the ign coil , thus isolating any of the wires from the lighting coil and neutral light.

Also Cynic, good point you made about manually operting the points to create a spark, I have actually tried this, no spark at the plug and to a lesser extent nothing at the contacts either.

Regards

Ardy

[JimR]

Hi All

Thanks for the info, I checked and double checked the timming and the points start to open around 1.8mm btdc, and the points were cleaned when fitted.

What method are you using to insure that the points open @ 1.8mm btdc ?

The main earth from the battery, (black wire) is fixed to one of the igntion coil securing bolts, and the coil plugs into a black and white wire its this wire from the stator that I'm getting voltage from by simply kicking it over.

Whats so odd about this fault is that I've taken a perfectly good stator and flywheel from a friends bike, fitted it to mine and nothing happens.

I'm well aware that these engines don't rely on battery voltage for ignition, so It should be so simple. To my way of thinking providing that I don't have the points going to permant earth, a spark should occur when they start to open. if the points are going to permanent ground it begs the question why?. The wiring loom is in excellent condition no sign of it ever being opened and you certainly cant get the plugs wrong.

I should add that I have dissconected the harness completly and isolated everthing else, I've also tried using single wire from the stator to the ign coil , thus isolating any of the wires from the lighting coil and neutral light.

Also Cynic, good point you made about manually operting the points to create a spark, I have actually tried this, no spark at the plug and to a lesser extent nothing at the contacts either.

That will work with DC ignition but with a flywheel mag you have no chance of creating a spark with this method as no voltage will be created in the ignition source coil (the one in the mag) unless the mag is spinning so therefore no current will be supplied to the condensor (the chances of having a charged condensor are slim) so therefore you will not a spark at the plug or points

Regards

Ardy

Other things to check over & above the HT coil earth & resistance could be the woodruff key on the mag (I'm sure this is fine) but if the crankshaft is allowed to spin without the mag being securley locked to it the ignition timming may dynamically alter

Regards Jim

[Airhead]

I know you checked the switches but try again with the kill switch disconnected followed by the ignition switch, see if you get a spark then!

[Cynic]

Hi All

Thanks for the info, I checked and double checked the timming and the points start to open around 1.8mm btdc, and the points were cleaned when fitted.

The main earth from the battery, (black wire) is fixed to one of the igntion coil securing bolts, and the coil plugs into a black and white wire its this wire from the stator that I'm getting voltage from by simply kicking it over.

Whats so odd about this fault is that I've taken a perfectly good stator and flywheel from a friends bike, fitted it to mine and nothing happens.

I'm well aware that these engines don't rely on battery voltage for ignition, so It should be so simple. To my way of thinking providing that I don't have the points going to permant earth, a spark should occur when they start to open. if the points are going to permanent ground it begs the question why?. The wiring loom is in excellent condition no sign of it ever being opened and you certainly cant get the plugs wrong.

I should add that I have dissconected the harness completly and isolated everthing else, I've also tried using single wire from the stator to the ign coil , thus isolating any of the wires from the lighting coil and neutral light.

Also Cynic, good point you made about manually operting the points to create a spark, I have actually tried this, no spark at the plug and to a lesser extent nothing at the contacts either.

Regards

Ardy

I know this kind of working iritates some but bear with me as this has worked in the past on the same problem i had on a DT 50m. There was a small plastic washer i had missed allowing the points to earth.

Get a nice long jumper lead from the positive on the battery and connect it to the coil breifly and dissconnect. Should generate a spark, thus proving the coil. Now connect the black white whatever wire that connects to the coil and spash the power on to the next point down in the harness, this should also generate a spark.

Carry on through the loom as necessary till you get to the points, where the coil stops showing a spark will be the problem,

I know its not exactly an approved Yamaha method but its effective in these older systems that dont have any electronics. Also make sure you have a fuse in the line , if there is a dead short in the system somewhere rather than a broken wire you dont want to fry the loom.

[Ardy]

Other things to check over & above the HT coil earth & resistance could be the woodruff key on the mag (I'm sure this is fine) but if the crankshaft is allowed to spin without the mag being securley locked to it the ignition timming may dynamically alter

Regards Jim

Hi All

I have checked the resistance of the primary and secondary windings of the ignition coil, they appear to be ok. earlier posts suggest that I check the ignition switch and stop switch, this has been done and their fine.

Earlier today I removed the source coil and checked the resistance of that its well within the +-10%. Re the woodfuff key, it is fitted and the flywheel dosen't spin on the crank.

Does anybody have any idea what AC voltage I should expect when I kick the bike over?

Regards a very depressed

Ardy

[kendo phil]

Does anybody have any idea what AC voltage I should expect when I kick the bike over?

Regards a very depressed

Ardy

If you are anywhere near somerset I am happy to have a look with you!

Phil

[JimR]

Hi All

I have checked the resistance of the primary and secondary windings of the ignition coil, they appear to be ok. earlier posts suggest that I check the ignition switch and stop switch, this has been done and their fine.

Earlier today I removed the source coil and checked the resistance of that its well within the +-10%. Re the woodfuff key, it is fitted and the flywheel dosen't spin on the crank.

Does anybody have any idea what AC voltage I should expect when I kick the bike over?

Regards a very depressed

Ardy

Hi Ardy,

I would guess forget about the ac voltage from the black/white wire. you will get that any way when I was taught that test was not required.. no spark tests were as follows :-

1) replace/check spark Plug

-> ok

2) replace/check HT cap

ok->

3) check/replace ancillary switches main/kill/side stand

ok->

4) Test/replace HT coil

ok->

5) check ignition timing & point condition

ok->

6) check/replace condensor

ok-> ignitoin works

but in the field the timming & point condition were checked first (it was assumed the ancilary switches would be fine)

if the points showed signs of burning or took along time to clean after cleaning them & setting the timming it would be good practice to check the condensor, then to coil.. and onto switches. You have not replied if the bike is fitted with the side stand/clutch switch so if fitted these may have gone o/s ( on this point if the neutral light bulb is blown or switch is o/c the bike will not spark as the bike will not start with the bike in gear (n light switch o/c or clutch switch if fitted o/c or bulb blown).

You mention in earlier posts that you connected the black/white directly to the coil if this has been done via the loom one of the fail safe will take over the only way to do this is to disconnect the plug & run a wire from the black/white mag side to the coil (this will bypass the kill/ignition switches you have connected via the loom). If you have done this I would guess that the igntion timming is incorrect or the condensor is at fault.

Regards Jim

[Ardy]

Hi Ardy,

I would guess forget about the ac voltage from the black/white wire. you will get that any way when I was taught that test was not required.. no spark tests were as follows :-

1) replace/check spark Plug

-> ok

2) replace/check HT cap

ok->

3) check/replace ancillary switches main/kill/side stand

ok->

4) Test/replace HT coil

ok->

5) check ignition timing & point condition

ok->

6) check/replace condensor

ok-> ignitoin works

but in the field the timming & point condition were checked first (it was assumed the ancilary switches would be fine)

if the points showed signs of burning or took along time to clean after cleaning them & setting the timming it would be good practice to check the condensor, then to coil.. and onto switches. You have not replied if the bike is fitted with the side stand/clutch switch so if fitted these may have gone o/s ( on this point if the neutral light bulb is blown or switch is o/c the bike will not spark as the bike will not start with the bike in gear (n light switch o/c or clutch switch if fitted o/c or bulb blown).

You mention in earlier posts that you connected the black/white directly to the coil if this has been done via the loom one of the fail safe will take over the only way to do this is to disconnect the plug & run a wire from the black/white mag side to the coil (this will bypass the kill/ignition switches you have connected via the loom). If you have done this I would guess that the igntion timming is incorrect or the condensor is at fault.

Regards Jim

Hi Jim

My DT50MX (82) is a very early bike and isn't fitted with with a side stand switch or neutral light switch that would inhibit the ignition. I,m gonna have to recheck the ignition timing I think, trouble is I dont have the DTI gauge to insert into the spark plug hole, Iv'e been doing it with a vernier depth gauge.

Am I right in thinking that at 1.8mm btdc the points should start to open?, then at maximum lift they should open fully to around 0.35.

[JimR]

Hi Jim

My DT50MX (82) is a very early bike and isn't fitted with with a side stand switch or neutral light switch that would inhibit the ignition. I,m gonna have to recheck the ignition timing I think, trouble is I dont have the DTI gauge to insert into the spark plug hole, Iv'e been doing it with a vernier depth gauge.

Am I right in thinking that at 1.8mm btdc the points should start to open?, then at maximum lift they should open fully to around 0.35.

Hi Ardy,

yep @ 1.8mm btdc the points should just open and forget anything else, if you get this setting correct the bikes timming will be correct I would think using a vernier guage will not be accurate enough if you are out by a mm you will get no spark (well at 3mm btdc ... thats close). I would guess the vernier could loose a mm easy as it is not sucurely held (hand wobble could loose a mm) and the only way really is to use a DTI. BTW what are you using to determine when the points open ?

Regards Jim

[Ardy]

Hi Ardy,

yep @ 1.8mm btdc the points should just open and forget anything else, if you get this setting correct the bikes timming will be correct I would think using a vernier guage will not be accurate enough if you are out by a mm you will get no spark (well at 3mm btdc ... thats close). I would guess the vernier could loose a mm easy as it is not sucurely held (hand wobble could loose a mm) and the only way really is to use a DTI. BTW what are you using to determine when the points open ?

Regards Jim

Hi Jim

Iv'e been connecting a light, It dosent go out like it did doing points on the old cars that had them it just simply dims when the points start to open.

I have a few DTI gauges but not the tool to hold it into the cylinder any ideas where I can pick one up?

Thanks

Ardy

[JimR]

Hi Jim

Iv'e been connecting a light, It dosent go out like it did doing points on the old cars that had them it just simply dims when the points start to open.

I have a few DTI gauges but not the tool to hold it into the cylinder any ideas where I can pick one up?

Thanks

Ardy

Yambits perhaps ? I bought a new DTI from them which came with the correct stand and a couple of extensions to the dial guage perhaps they also have just the stand ?

How did I know you were using a battery/bulb set up .... <G> as I know this will not work well enuff, the ohm meter that Yamaha supplied was something else (well sensitive) and could detect the points breaking battery & bulbs do not ! so without a good ohm meter you would be better off using a fag paper and a DTI. unless you know to an ohm meter that will actually put up with the spike from the mag as you turn it (most digital meters seem to go into shock !) and do not record when the points open. As I dont have the correct meter I am using the fag paper method until such point (excuse the pun) as I can find a Yamaha meter .. I'm now looking at outboard suppliers as the bike people look at you 'gone out' !

Regards Jim

[Ardy]

Yambits perhaps ? I bought a new DTI from them which came with the correct stand and a couple of extensions to the dial guage perhaps they also have just the stand ?

How did I know you were using a battery/bulb set up .... <G> as I know this will not work well enuff, the ohm meter that Yamaha supplied was something else (well sensitive) and could detect the points breaking battery & bulbs do not ! so without a good ohm meter you would be better off using a fag paper and a DTI. unless you know to an ohm meter that will actually put up with the spike from the mag as you turn it (most digital meters seem to go into shock !) and do not record when the points open. As I dont have the correct meter I am using the fag paper method until such point (excuse the pun) as I can find a Yamaha meter .. I'm now looking at outboard suppliers as the bike people look at you 'gone out' !

Regards Jim

Hi Jim

Thanks for all your advice, I managed to get myself a DTI gauge and some fag papers, set the timing as per your instructions, second kick it started.

You'd da man

Thanks

Ardy.

[JimR]

Hi Jim

:angry:Thanks for all your advice, I managed to get myself a DTI gauge and some fag papers, set the timing as per your instructions, second kick it started.

You'd da man

Thanks

Ardy.

Hi Ardy,

glad you got the old 'beast' going.. using a fag paper takes me back to 70's .. they guy at the collage I studied at used this as a 'get you home' method but as I still cannot find a meter I'll just have to set little 2 strokes up this way. I notice you have FS1's also they will be setup the same ...

Regards Jim