1981 series 2 with dmc fault

B

brooky

Junior member
Location
PETERBOROUGH
Hi all ,i have now had a chance to take a look at my bike again ,after 4 months standing House move etc, i was sent the wiring diagram for the dmc also downloaded from owners club a colour version. i have power at the coils both sides? the kill switch works as should i even bypassed to make sure , all wire colours are as colour diagram shows, the dmc box is earthed direct to battery as per diagram. power at terminal 8 on dmc box which in turn goes to coils 12.7v and 12.6v i have put dmc box into test position 0 and turned by hand and by starter no spark does anyone know if / who box can test the box ? or how to test the photocell? or if the box still sparks if photocell is phucked? TIA
 
Hi Brooky,

I'm sure someone more knowledgeable than me will be along soon, can you or have you tried this test ?

4.1 Functional test
The basic functionality of the DMC/2 module and the electrical connections can be easily checked with the test program of the LAV1000 software.
1.Leave the ignition switched off!
2.Unscrew spark plugs out of the engine and plug them into the candle plug. Shield the candle plug and place the spark plugs on the engine.
3. Bring the encoder switch to position 0. (See Chapter 6.4 from the manual DMC/2 module)
4. Turn on the ignition. (Under no circumstances the ignition cables or the
Touch the candle plug, as dangerous high voltage is created.)
5. Now, for testing purposes, an ignition spark can be triggered on the respective cylinder if the flat side of a medium-sized screwdriver is first moved towards the pulse generator coil and then pulled away again. The impulse should be triggered exactly when the screwdriver is pulled away again. (Otherwise, the connections of the pulse generator coils are reversed!)
 
Hi steve . thanks for the reply . its a system that came on the bike the bike had been down the road on the alternator side and broken the alt case and leaked oil so i never had it running , i didnt know about the test you describe i can try that .i only understood that you put the switch into 0 position and turned ignition on while turning the engine over ,i know that there was a spark as i spun the engine over in the dark last year when i put the battery on. i can get an hour on it tomorrow afternoon so will try as above. Regards Paul
 
I think Schurminator has inadvertently given you the test procedure for the series 1 bike with Bosch alternator and integral ignition triggers.

It's a bit different and easier for a series 2 bike -

1. Put the microswitch on the computerbox to position 0.
2. Remove and put the spark plugs in the plug caps.
3. Ground the plugs on the cambox cover.
4. Switch on the ignition. Manually turn the ignition rotor clockwise and you should have a continuous spark when the cutouts in the rotor pass the photocell.

Do not touch the sparkplugs when doing this test!

Full installation and test details are here -
Library link
 
Thanks Rob for stepping in and pointing that out, I just had a quick glance at the instructions for any guidance.
Hopefully on the right track to success now 👍
 
Power on both sides of the coils is correct. the spark is innitiated by grounding the output at the right timing by the DMC IIRC.

If it was down on the road with the alternator cover broken, expect damage on the crank bearings (guess how I know...). At least keep an ear on the bike, if it develops a nasty noise when running (might appear over time...), it is engine out-time...

Hope to be wrong, but with my bike that was the case... (also series 2 180°). I'll cross my fingers for you!!
 
Hi all , ongoing fault finding on dmc 2 Re cap. after checking coil good 12v ,good earth ,power at dmc box ,box earthed direct to battery as fitting ins
and putting the dmc box into position 0 and turning ignition rotor clockwise while earthing plugs ,rotor veiwed from left, still no spark , can i check the pick ups just by disconnecting from the box 3 wires and metering ? would anyone know what readings i should be seeing ? the 3 wires are a yellow a brown and a black. any input would be appreciated.
 
So just to be clear - you had no sparks when the rotor cutout aligned with the sensor?

There are no 'pickups' (plural) to check. On a DMC2 there is an infrared photocell that is triggered by the rotor slots as per your earlier post on 12 April. I have no information about how to test the photocell - I would simply substitute it with a known good replacement. Similarly for the DMC2 box. However, I understand that Uwe Witt will test the unit if you send it to him in Germany. Much quicker and less risk of the box being lost in transit/caught in customs if you can borrow a known working item. Or get another 180 DMC2 user to test yours on their bike.

A known fault that has affected some users is a break in the wiring at the multipin plug on the DMC box. Very difficult to see - the stranded conductors break whilst the PVC sheath remains intact. Given you have no sparks, I'd check that you have 12v on the top two pins (8 & 16) of the connector. Thin voltmeter probes can make contact with the top of the connector pins without disturbing the wiring or connector itself.
 
Swapping boxes as described above is the easiest and quickest way to narrow down the problem. The sensors are cheap and available from sellers of Witt boxes or from electronic suppliers. Do a search on this forum, there was a lot of discussion which product # it was and where to purchase awhile back.
 
Quick check using "Witt Sensor" brings up a fair bit of info.......good luck

DMC optical sensor warning!

My series 2 Jota has been of the road for 5 weeks. The crank sensor on the Moto Witt ignition failed. The part is made by Honeywell and is no longer made. I tried in the UK, but no luck. Tried Italy no luck. At long last Moto Witt had found one old stock. The problem occurs that sending a parcel...
laverdaforum.com laverdaforum.com
 
Laverdalothar said:
Power on both sides of the coils is correct. the spark is innitiated by grounding the output at the right timing by the DMC IIRC.

If it was down on the road with the alternator cover broken, expect damage on the crank bearings (guess how I know...). At least keep an ear on the bike, if it develops a nasty noise when running (might appear over time...), it is engine out-time...

Hope to be wrong, but with my bike that was the case... (also series 2 180°). I'll cross my fingers for you!!
Click to expand...
Hi thanks for the input on the ignition .i have not had any spare time to check but hope to tomorrow ,regards the engine damage i clocked the rotor and no run out that was concerning ,fingers crossed !!!
Schurminater said:
Quick check using "Witt Sensor" brings up a fair bit of info.......good luck

DMC optical sensor warning!

My series 2 Jota has been of the road for 5 weeks. The crank sensor on the Moto Witt ignition failed. The part is made by Honeywell and is no longer made. I tried in the UK, but no luck. Tried Italy no luck. At long last Moto Witt had found one old stock. The problem occurs that sending a parcel...
laverdaforum.com laverdaforum.com
Click to expand...
Thanks will have a bit more time 0n it today again, will search for info as you suggest , regards Paul
 
Rob said:
So just to be clear - you had no sparks when the rotor cutout aligned with the sensor?

There are no 'pickups' (plural) to check. On a DMC2 there is an infrared photocell that is triggered by the rotor slots as per your earlier post on 12 April. I have no information about how to test the photocell - I would simply substitute it with a known good replacement. Similarly for the DMC2 box. However, I understand that Uwe Witt will test the unit if you send it to him in Germany. Much quicker and less risk of the box being lost in transit/caught in customs if you can borrow a known working item. Or get another 180 DMC2 user to test yours on their bike.

A known fault that has affected some users is a break in the wiring at the multipin plug on the DMC box. Very difficult to see - the stranded conductors break whilst the PVC sheath remains intact. Given you have no sparks, I'd check that you have 12v on the top two pins (8 & 16) of the connector. Thin voltmeter probes can make contact with the top of the connector pins without disturbing the wiring or connector itself.
Click to expand...
Hi Rob , yes no spark when rotated clockwise i also checked with the rotor cut out aligned with the photo cel .i will remove the photo cel and check for a broken wire etc . i will double check for 12v at the pins 8- 16 i am sure i checked but will double check , and then see if there is anyone willing to check dmc box . regards paul
 
Just to emphasise that the DMC2 test function needs the photocell to be in its triggered state... that is, aligned with a slot in the rotor. Doesn't matter about direction of rotor travel to get to that point (unlike Ignitech).
 
Update , i now have a whoppa spark , found the fault broken wire inside some heats shrink tested ok until i connected it iback onto the bike, as i cable tied it back to the loom and re tested no continuity again removed all the heat shrink and bingo the wire had been soldered very neatly possibly when the dmc was fitted as all the joins look to be same type on the ignition system thick wall heatshrink on the whole of the wires. thanks to all again.
 
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