IIS
Full member
Lads, pile of test equipment picture, Tektronix 561( A? ) on the bottom left front, maybe a cosser cro on the top, 3" tube.... or not... not quit Los Alamos grade... maybe the TEK...
You could make your own test jig, for Variable Reluctor ( VR )pickup testing. Two Leds ( red and green or blue etc ) wired ( reverse ) ie anti parallel with 470 Ohm resistor in series with each. Sling the circuit across the VR output leads, plugs out and crank the engine on the starter, ( dummy load the HT leads with plugs on the caps and resting against the block ). You will see a sequenced pulse train as you crank, first led to light will be the positive going pulse, very soon after will be the negative pulse. VR's can put out up to 80V peak unburdened ie you need to keep them loaded when being pulsed by the impulse cam lobe, for least harm to the VR windings. The leds will light at about 1.5 to 2.0 volts amplitude from the VR, which is akin to the internal trigger thresehold on the HKZ.
DMM measure ( quantify ) by various techniques, not all will indicate a true representation of output pulse shape or magnitude.
Timing light(s), some will not trigger properly unless you note the director on the inductive clamp probe. The Plug symbol points towards the plug. HKZ is a capacitor discharge circuit and has very fast pulse rise times, which can cause misoperation of the timing lamp. Another feature can be a closed throttle lean out shunting most of the spark energy out of the HT lead, ie as you blip the throttle the timing lamp misfires or shuts off completely on the throttle closing. Also the wasted spark adds to the fun factor, with reflected pulse waveforms or standing waves on the HT lead wire(s) on alternate pulses.
Good luck reading that DMM taped to the tank, personally i wonder how you read it and look at the road. If indeed that is what happens, ignore me if not the case. Know which is the most important to me. You only have a engine problem at the moment, not a prolonged hospital stay and wrecked bike, if lucky.
HTH John.
You could make your own test jig, for Variable Reluctor ( VR )pickup testing. Two Leds ( red and green or blue etc ) wired ( reverse ) ie anti parallel with 470 Ohm resistor in series with each. Sling the circuit across the VR output leads, plugs out and crank the engine on the starter, ( dummy load the HT leads with plugs on the caps and resting against the block ). You will see a sequenced pulse train as you crank, first led to light will be the positive going pulse, very soon after will be the negative pulse. VR's can put out up to 80V peak unburdened ie you need to keep them loaded when being pulsed by the impulse cam lobe, for least harm to the VR windings. The leds will light at about 1.5 to 2.0 volts amplitude from the VR, which is akin to the internal trigger thresehold on the HKZ.
DMM measure ( quantify ) by various techniques, not all will indicate a true representation of output pulse shape or magnitude.
Timing light(s), some will not trigger properly unless you note the director on the inductive clamp probe. The Plug symbol points towards the plug. HKZ is a capacitor discharge circuit and has very fast pulse rise times, which can cause misoperation of the timing lamp. Another feature can be a closed throttle lean out shunting most of the spark energy out of the HT lead, ie as you blip the throttle the timing lamp misfires or shuts off completely on the throttle closing. Also the wasted spark adds to the fun factor, with reflected pulse waveforms or standing waves on the HT lead wire(s) on alternate pulses.
Good luck reading that DMM taped to the tank, personally i wonder how you read it and look at the road. If indeed that is what happens, ignore me if not the case. Know which is the most important to me. You only have a engine problem at the moment, not a prolonged hospital stay and wrecked bike, if lucky.
HTH John.
L
laverlesmains
Guest
John
That does help - I actually understand most of what you wrote !
I am using a DMC2 - does it have a threshold voltage limit as well?
Cheers, Tim
That does help - I actually understand most of what you wrote !
I am using a DMC2 - does it have a threshold voltage limit as well?
Cheers, Tim
L
laverlesmains
Guest
where are the ballast resistors?
3
3patC
Guest
You dont have them on a 3C.
IIS
Full member
This is bizarre, how many times can it be stated the current limit resistors have no effect on a running engine! These BTZ module protection resistors effect cold cranking starts only. Been stating this on forums for 10 years or more. I Give up.
This is not a difficult fault or faults to diagnose, it is the lack of understanding that stands at the gates. Take some time to observe the problem, gather the information and then make informed choices.
** In the unlikely event there are red motoplat coils fitted, bin them. No question. Were on 120 motors only, should not be on any 180. 3c can have limit resistors fitted, where a BTZ was original equipment.
Regards John.
This is not a difficult fault or faults to diagnose, it is the lack of understanding that stands at the gates. Take some time to observe the problem, gather the information and then make informed choices.
** In the unlikely event there are red motoplat coils fitted, bin them. No question. Were on 120 motors only, should not be on any 180. 3c can have limit resistors fitted, where a BTZ was original equipment.
Regards John.
IIS
Full member
laverlesmains said:John
That does help - I actually understand most of what you wrote !
I am using a DMC2 - does it have a threshold voltage limit as well?
Cheers, Tim
Hello Tim,
Never seen inside a DMC series one or two. That is serious German potting in use, grin. Most designers of electronic ignitions follow well proven design criteria, unless something extra clever is discovered. VR's have a natural inbuilt "advance" of some 12 degrees in 360, if you allow the full voltage wave shape to be utilised. This can interfere with the design concept of a "digital" ignition, ie we want zero error from the sensor or pickup of choice. We do this by clamping the trigger point close to the base of the voltage wave shape. Very peaky wave form from VR's and the base shape is fairly flat for the major part of the active trigger waveform, when pulsed by the impulse cam lobe.
Can become very technical if i continue from this point, hope the above serves as the basis for a useful understanding, to allow fault or operational diagnoses or confirmation. The module trigger point can be assumed to be less than one volt in digital design, due to the low trigger voltage on slow cold cranking starts ie sagging battery voltage, coupled with highly variable Total Effective Air Gap ( TEAG ) of impulse cam lobe to VR pole face(s), 0,25m/m or 10mil is usual for reliable cold crank starts. This equates to a certain VR output of some 250mV ( 0,25Volt ), an industry minimum output trigger level designation. Let me know what is not clear, if any, it is a bit technical the above.
On the IIS crank encoder sensor system i ditched voltage sensing concept in 1997. Use current sensing ie vary voltage does not effect the accuracy of the crank angle sensor/encoder. Also the IIS allows static ignition timing, that is you can set the timing on a stationary engine and it will be exactly the same at 10Krpm or higher, for you thrill seekers, grin. I do make IIS for use with VR's as per Ducati with engine internal VR's running in hot engine oil.
HTH John.
Tetley Laverda
Senior member
I have a 1978 180 Jota with a DMC 2 fitted .In laymans terms what do ballast resistors do and should I be using them . If so where should they be fitted and what value should they be
Kind Regards
Tetley
Kind Regards
Tetley
Dellortoman
Hero member
- Location
- Tasmania, Australia
IIS said:
As a mere pleb questioning the wisdom of The Great Ignition Guru, I'll propbably be cast out of the forum as a heretic. But, are you sure about that John?
The resistors are normally bypassed during cranking to offset voltage sag caused by the starter motor, but are in circuit during normal running.
I say "normally" because that's the the way most cars and bikes are wired. However, the wiring diagram for BTZ Laverda triples shows that the resistors are in the circuit all the time - ie. never bypassed. Not sure what the logic is there.
Cheers,
Cam
IIS
Full member
Dellortoman said:
Hello Cam, Tetley.
Power semiconductors were an emerging technology back in the late 1960's, we really only had Germanium PNP type semiconductors, there was no complimentary NPN. Into the 1970's and we had Silicon wafer technology to replace the Germanium prone to thermal runaway, ie self destruct. Legacies were carried over into emerging technologies, and to make a story short the NPN Si power transistor had some hideous characteristics, compared to todays power devices. One such characteristic was Vcesat, the voltage drop across the transistor emitter to collector, when fully conducting. If you multiply this Vcesat by the collector current you get Pd or Power dissipated by the die inside the can of the power device.
It does not take a lot of current with a high Vcesat to broach the SOA or Safe Operating Area of a power device. This is my interpretation of why Bosch slung an extra resistor of 0,9 Ohms in series with the DC resistance and impedance of the ignition coils of the day. Suppose Bosch did not know for certain what was going to be connected to the BTZ as it was used not just on Laverda's.
With ND coils these are rated at 12V ( 13,8 V really ). You loose some 2 odd volts at the BTZ due to what all you clever blokes now know as Vcesat losses. Half a volt here and there, even more usually, with ageing wires and connections, worn out fuses, lossy ignition switches, dirty Run/Stop switch. Sagging battery volts on cold crank and it is a wonder the Laverda starts at all! Once a coil is at 9V on the primary winding the saturation current ( which generates the actual spark energy on switch off for inductive discharge systems ie BTZ ) is much less. Feeble spark is the result ( BTZ's only produce 15KV on the plug gap, modern digital ignitions, at least 25KV, why you only ran a BTZ plug for a few thousand miles and the plug would not fire at 15Kv on cold crank ). This was well known for cars and the "Ballast resistor was born"
The ignition coil is now rated at 9V ( allows for cold crank battery terminal voltage sag ) and a 3-5 volt dropping resistor is added to the primary circuit to stop the 9V coil overheating and failing quickly, on a running motor with proper charging system working. Shorted out at cold crank is this resistor. So, the commonality between the BTZ and car ballast resistor function is zero. Totally different reasons for a seemingly "the same function resistor"
All the above parlava can be replaced by the term "bin those bloody anti start resistors", even on a BTZ i have removed them and ran the Ducati's fine. Been a long day...hope i make sense.
Regards to all.
Dellortoman
Hero member
- Location
- Tasmania, Australia
Makes perfect sense. Thanks again for your wisdom John. Where did you learn all this stuff?
Cheerrs,
Cam
Cheerrs,
Cam
IIS
Full member
Dellortoman said:
It does? Amazing...
.Was a consultant on Ramesses II chariot racing team, he knew 3 horse team had the h/p over the twin horse rigs, centre horse at the front and the outside two a horse length behind... yer i know, its the best i can do for humour, better i stick to electrons or holes moving about...
. Regards from John.
Tetley Laverda
Senior member
Many Thanks
Tetley
Tetley
L
laverlesmains
Guest
well I may have found the culprit... Trigger for the outer plugs seemed to be the one was the problem.. I stripped back the wiring that a PO had done and found this:
My guess is that they tried to solder the new wire to the old pickup wire without cleaning all the grunge from the old wire, which meant that the solder didn't flow into the wires and create a good joint. I'm guessing that at a certain RPM the connection vibrates loose and that's what's causing the DMC to have a spasm. Seems to rev nicely in the garage, will button it all up and take it for a spin later.
My guess is that they tried to solder the new wire to the old pickup wire without cleaning all the grunge from the old wire, which meant that the solder didn't flow into the wires and create a good joint. I'm guessing that at a certain RPM the connection vibrates loose and that's what's causing the DMC to have a spasm. Seems to rev nicely in the garage, will button it all up and take it for a spin later.
Rob
Hero member
- Location
- Midlands, UK
That would explain it! Well done....enjoy your test ride 8)
L
laverlesmains
Guest
or not.. hmmm.. in the garage, I rev it up and at 5000 (1/4 throttle) it breaks up. If I continue to twist the throttle to about 1/2 way it kicks back in at 5500-6000 and revs clean.. while there may be electrical and timing issues, it may also be the needles? 1/4 throttle is where the needle & main jet starts as it transitions off idle jets?
I'd replaced the emulsion tube and main jet when rebuilding, but not the needles... I guess the carbs have to come off to move the needles up a notch or two? Or can it be done in situ.
I'd replaced the emulsion tube and main jet when rebuilding, but not the needles... I guess the carbs have to come off to move the needles up a notch or two? Or can it be done in situ.
Rob
Hero member
- Location
- Midlands, UK
When you say emulsion tube, do you mean atomiser? In other words, the jet in which the needle slides up & down? There are now long and short versions of these (the shouldered section above the threaded part differs) - make sure you have the correct one by checking length against the ones you removed. Worth double checking the jet size too (AB265). Replacing the jet but leaving the needle is not a good plan - both wear.
It is possible to change the needle position with the carbs on the bike. You need to remove the top cap assembly (two bolts) which will withdraw the throttle slide and needle too. Lift the spring on to the top edge of the slide to clear the needle and circlip. Push the needle up to remove from the slide and change the clip position. However, I doubt that needle clip position is having such a dramatic effect on engine running. Nor the main jets - these kick in around three quarter throttle.
Are all the carb pilot/progression drillings are clear? Here's how to check http://www.laverdaforum.com/forum/index.php?topic=55154.msg102290#msg102290 What are your accelerator pumps doing?
Were you running the overhauled carbs with your original ignition - were they OK then? Or did you overhaul them at the same time as fitting the DMC? Are the carb manifolds OK and not cracked? How about the carb bodies?
Final thought - with all the trigger wiring issues, are you absolutely certain that the wiring polarity is the same for both? Have you checked timing on both outer & centre cylinder with a strobe: does it advance when it should? What happens when the engine 'breaks up'?
It is possible to change the needle position with the carbs on the bike. You need to remove the top cap assembly (two bolts) which will withdraw the throttle slide and needle too. Lift the spring on to the top edge of the slide to clear the needle and circlip. Push the needle up to remove from the slide and change the clip position. However, I doubt that needle clip position is having such a dramatic effect on engine running. Nor the main jets - these kick in around three quarter throttle.
Are all the carb pilot/progression drillings are clear? Here's how to check http://www.laverdaforum.com/forum/index.php?topic=55154.msg102290#msg102290 What are your accelerator pumps doing?
Were you running the overhauled carbs with your original ignition - were they OK then? Or did you overhaul them at the same time as fitting the DMC? Are the carb manifolds OK and not cracked? How about the carb bodies?
Final thought - with all the trigger wiring issues, are you absolutely certain that the wiring polarity is the same for both? Have you checked timing on both outer & centre cylinder with a strobe: does it advance when it should? What happens when the engine 'breaks up'?