DMC ignition

S

Simplex

New member
Location
Holland
Hello,

I have a DMC 2 ignition installed 4years ago on my RGS but experiencing trouble which I think is electronics. When I start the bike it sometimes fires at will resulting in awful starter clutch noises. I thought it was a bad battery and replaced it with a pc680 but it didn't change. I'ts better when I put the setting on 9 but I want it running on 10. But lately the bike just stops running (3x), lights etcetera are working, and when I turn the ignition off and then on it happily fires up...also while riding the bike it misses a few sparks ones in a while and then continues, like turning the kill switch.
In my 'frustration' I soldered and checked every connection and checked the voltage in different places, it's already a more than 30 year old bike.
I saw the topic from a few years ago about the DMC and that it gave trouble but it's not clear to me how the trouble occurred.
Has anyone suggestions where to look in the system or what to do?
I am afraid to fire up the bike now because of ruining the starter clutch.

Simplex.
 
If you've checked everything outside the box, probably best to send it back to Herr Witt for testing, if only to be sure.  My RGS became very reluctant to start all of a sudden which was traced to a fault in the box (after less than one year) and was replaced without hesitation.  Dunno how a four year old box would be viewed.
 
I have had a few problems with the Witt on my RGS over the years. First was the optical sensor got wet....turns out the ignition cover on my RGS was the wrong one (off a 500 I think) and some moisture got in there. Replacing the sensor fixed that problem. Years later a strange problem where the bike when running for an hour or so at relatively constant speed would feel like it was running on 2 cylinders, but changing RPM would "clear it" Eventually it stopped firing on the middle cylinder altogether. A replacement box fixed the problem but immediately had a problem of its own, it would start misfiring at about 6000 RPM.  Another replacement box and all was well again. These problems were over the course of 15 years or so.  Some comments offered to me were to check the connections between the wiring and the pin connectors at the large connector going into the Witt...there had been some bad connections made on some units. As suggested once you have checked everything you can, try another unit. 
 
Are you saying the starter engages while the engine is running, or does not disengage after the bike has started?   

I had a weird, intermittent, starting problem on my 3C where sometimes battery seemed not to want to turn over the motor, or the starter would not disengage after starting.    I suspected the battery, but eventually traced the problem to a poor fuse connection and a starter relay problem.
Nothing to do with ignition, I know, but may be worth checking.

Tom
 
I had a very similar problem, I fiddled around with all sorts of things but I very strongly suspect that I had a poor connection somewhere, more than likely an earth.

Took some wiring off, put it back on again - problem disappeared !!!!!
 
If the starter engages, this has absolutely nothing to do with the ignition box, the starter isn't wired via the DMC. This would be probably a faulty relay or a shorting in the wiring loom somewhere between the starter button and the relay. or inside the right hand switch unit on the bike.

In this case it sounds like there is one of the little pins in the 30 pin connector either broken or just came off it's seat. We had that several times, hard to find really... often happens if you zip-tie the cables without leaving a bit of flexibility. The bike - and especially the 120?... - vibrate in 2nd order which destroys almost everything...

Check your engine mounts are all properly torqued and check the cables on the 30 pin connector. Also check the fuses in the fuse box and that the connectors to hold them tightly. My brother once got hold of an SFC 1000 that had exactly that issue, it was a fuse that was ratteling between two contacts when the engine ran. took the fuse out, bent the contacts a bit more to eachother and put the fuse back in - problem solved.

good luck!!
 
Thanks for the reply's, very helpful! appreciate it.
I now know they are not troublefree!
tom3c75, the starter function's normally, it engages and disengages on command(starterbutton). What I was trying to say is that the ignition fires at a wrong moment during starting, to my idea it pushes the piston the other direction while the starterclutch's is doing it's job causing awful sounds..It's like the system has to figure out where cilinder 1 is..the voltagereading while crancking is about 11,5V, which is enough for the ignition.
I'll check the earth again, I changed the fusebox, with modern fuses, years ago. They are still clean and I have a good reading on those.
Laverdalothar, I'll check the 30 pin connector but if that is fine I'll make a direct connection from battery to red wire going to the coils and ignitionbox, ofcourse with a fuse in between...
If problem is still there I'll send the box to be checked.
I'll keep you all informed.
Simplex.

 
Simplex said:
Hello,

I have a DMC 2 ignition installed 4years ago on my RGS but experiencing trouble which I think is electronics. When I start the bike it sometimes fires at will resulting in awful starter clutch noises. I thought it was a bad battery and replaced it with a pc680 but it didn't change. I'ts better when I put the setting on 9 but I want it running on 10. But lately the bike just stops running (3x), lights etcetera are working, and when I turn the ignition off and then on it happily fires up...also while riding the bike it misses a few sparks ones in a while and then continues, like turning the kill switch.
In my 'frustration' I soldered and checked every connection and checked the voltage in different places, it's already a more than 30 year old bike.
I saw the topic from a few years ago about the DMC and that it gave trouble but it's not clear to me how the trouble occurred.
Has anyone suggestions where to look in the system or what to do?
I am afraid to fire up the bike now because of ruining the starter clutch.

Simplex.
Click to expand...

Starter clutch noises are only sometimes indirectly ignition-related.  A weak battery will not spin the starter properly, which lowers the current available to the ignition box, causing it to generate wrong signals, which in turn causes back-firing, which eventually fucks up the starter freewheel big-time.  Once the starter clutch is knackered, the engine should NOT be run.  Bits of starter clutch components can escape and jam in the alternator, wrecking it on the way.

Different advance curves will have no effect on starting behaviour.

Check/repair the starter clutch, install a known good battery, check earths and starter current supply, and then worry about the ignition.

piet
 
Hello sfcpiet,

As I noted before, I checked the connections and measured the starter current supply, that's why I worry about the ignition. The startermechanism is still fine, I tested the bike yesterday but the startingnoises occure sometimes, about 3x out of 10 startingattempts. This winter (in Holland we are not allowed to drive a classic for 3 months.....) I had a look at the starterclutch and took the generator etc. off. It looked fine thank god!
And yes, nr.9 ignition curve is really different, the advance is less, also at lower RPM!
The original system never gave me this trouble, it only run rough...
Simplex
 
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