DMC 2 ignition on a mk1 180 Jota.

B

Brian P

New member
Location
Exeter
Hi, this is my first post, please excuse me if I haven't done this correctly!

I have a mk1 180 Jota fitted with a DMC2 ignition system. The bike runs on two cylinders most of the time and will never idle, also prefers to have the choke on. I am of course going to check the carbs, but I also need to check the ignition. Does anyone have a wiring diagram please, and a detailed explanation of how the system works?
 
Hope the Laverda meets all your needs, when running properly, a smile here. Searching the forum is a good start ( no pun intended, well sort of ), to get you started, which cylinder in not firing up? Measure ( water drops on header to see which one is cold ), good news is one of the outside, not so good the center cylinder. Short answer as its 6:30am as i type... tea pot beckons, j

*** oh and put 3 new plugs in NGK B8ES, no matter what was in there, just had my hard to start 79 Jota give me grief, days later after blaming the ignition bloke, 3 new plugs fitted...on the button all three in voice...plugs were only 13 years old, barely into puberty...
 
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iis_iis said:
Hope the Laverda meets all your needs, when running properly, a smile here. Searching the forum is a good start ( no pun intended, well sort of ), to get you started, which cylinder in not firing up? Measure ( water drops on header to see which one is cold ), good news is one of the outside, not so good the center cylinder. Short answer as its 6:30am as i type... tea pot beckons, j
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Thanks, I'll get a bit more information on the fault, I have found some details here of the DMC2. I have to remove the motor anyway, as I have an oil leak from the cylinder Base, something that the previous owner tried to fix with a new gasket, but still leaking. I was just hoping to get the motor running better before I started on the top end work.
 
If the bike runs on 2 cylinders i'm guessing its the 2 outers, these two are linked to the double coil under the tank ,the middle pot is associated with the front positioned ( of the two) single coil, my first port of call would be checking the connections of the HT leads into these coils...but i'm sure folks far more knowledgeable than me will be along soon.
 
philw said:
If the bike runs on 2 cylinders i'm guessing its the 2 outers, these two are linked to the double coil under the tank ,the middle pot is associated with the front positioned ( of the two) single coil, my first port of call would be checking the connections of the HT leads into these coils...i;m sure folks far more knowledgeable than me will be along soon.
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Many thanks for your advice, I've managed to find a wiring diagram, so I'll check through the low tension side as well as the HT leads, cheers.
 
iis_iis said:
Hope the Laverda meets all your needs, when running properly, a smile here. Searching the forum is a good start ( no pun intended, well sort of ), to get you started, which cylinder in not firing up? Measure ( water drops on header to see which one is cold ), good news is one of the outside, not so good the center cylinder. Short answer as its 6:30am as i type... tea pot beckons, j

*** oh and put 3 new plugs in NGK B8ES, no matter what was in there, just had my hard to start 79 Jota give me grief, days later after blaming the ignition bloke, 3 new plugs fitted...on the button all three in voice...plugs were only 13 years old, barely into puberty...
Click to expand...
Thanks, I hope you enjoy your cuppa!
I had a Mirage a couple of years ago with a similar issue, turned out to be very low voltage reaching the coils, but the plugs would foul at the drop of a hat and replacing them was the only cure, despite them being relatively new.
 
Hi Brian and welcome to the site.

I hope you get to the bottom of your oil leak,I also run the DMC system on my Mk 1 Jota and have a wiring diagram and some installation instructions translated into English should you need it.
Its a good idea to see what setting the control module is set too, No. 10 seems to be a good one and I have been running mine on this since setting it up 5 or 6 years ago.

Does sound like you may have carb issues too which you say you are going to look into, NGK plugs are very temperamental these days and hate getting wet so choke off as soon as you can..........I now run on Denso equivalent which have been more reliable and for some reason mine hates Shell Super unleaded!

Anyway good luck and keep us posted.

Steve
 
Schurminater said:
Hi Brian and welcome to the site.

I hope you get to the bottom of your oil leak,I also run the DMC system on my Mk 1 Jota and have a wiring diagram and some installation instructions translated into English should you need it.
Its a good idea to see what setting the control module is set too, No. 10 seems to be a good one and I have been running mine on this since setting it up 5 or 6 years ago.

Does sound like you may have carb issues too which you say you are going to look into, NGK plugs are very temperamental these days and hate getting wet so choke off as soon as you can..........I now run on Denso equivalent which have been more reliable and for some reason mine hates Shell Super unleaded!

Anyway good luck and keep us posted.

Steve
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Hi Steve, thanks. I think I may have found what I need, but I'll give you a shout and keep you posted. So far I have found that my unit is set to no.1.
With the ignition stator and trigger being inside the rotor, can the engine be run with the rotor off do you know?
 
Hi Brian,

If i'm not mistaken No 1 position is used to check the timing with 32 degrees maximum advance.....see notes below.

4.3 Test run

Check the mechanical attachment and wiring again.

Select ignition adjustment curve 1 with 32 degrees maximum early ignition at the coding switch.

Start the engine with the starter motor and let it warm up.

. Let the engine turn to approx. 4000 rpm and check the ignition adjustment at the mark with the stroboscope.

(At approx. At 1000 rpm, the ignition spark constantly moves back and forth between OT and about 8 degrees of OT because the idle control is active. As the speed increases,

the early ignition then continuously goes in the direction of early until the maximum early ignition is reached from about 3000 rpm. (Only at turn 1!)

As for running with the rotor off?.........I've never tried that!......you would obviously have no charging?
 
Hi, yes, I just thought that while setting up and making adjustments running with the rotor off would make life easier, were it possible. I've not had the bike long and never ridden it because of the oil leak and the poor running. The ignition advance switch was set to position 1 by the previous keeper I guess. I am going to strip and ultrasonic clean the carbs, check the connection and wiring at the stator and check the ignition timing. Thanks for your help!
 
...just a thought for the DMC that do not operate correctly intermittently, in the main voltage sensitivity, for high volts mitigation, a small added vero board addition of an LM2931 adjustable low dropout voltage regulator in TO-220 package would prevent excess voltage excursions and protection against load dumps, shedding. Would not compensate for low volts issues with the internal regulator if it has one or of the usual 7812 derivative series reg.

Would of course preclude the supply of the ignition coils primary daisy or star chain connection to 12V vehicle. Just a thought j
 
 
As stated, you need to identify which cylinder isn't firing. A quick dab of a finger on each header pipe will do that.
After replacing all 3 plugs and HT caps, if the problem persists you need to check the wiring of the pickup triggers which if original will likely have deteriorated. A quick check of the resistance of each coil will help identify a problem.
I'm assuming you have fresh petrol in the tank. It's also best to check valve clearances are correct and balance the carbs before getting too far into fault diagnosis. This includes float levels.
 
.... and maybe a quick compression test, wet and dry...... spent a few hours on a motor issue, a compression test would have saved me half a day, dont forget to WOT for maximum air intake, j
 
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