Topic: Do I need spark units in my new m-Unit wiring system?

[anthograham]

Hello all,

I'm in the process of installing a motogadget m-Unit Blue on my 81' CB650 Custom. However, it is not clear to me if the spark units from my old wiring system need to remain in the new system. Based on the research I've done, it looks like I can ditch them. Hopefully, someone with more knowledge than I can clarify if I need them in my new system.

Thank you for any and all information!

[scunny]

Only if you can ditch the points on earlier bikes, I know nothing about the M Unit, but have never heard of it making them redundant.
If I'm not wrong, it operates as a "switch" so, Ignition on, lights etc
Not meant to be an "ignition system"
Cal will prove me wrong no doubt.

[caluser2000]

Yes, follow the CDI approach. Yes, the relay is my reference.

I'm going to revive this thread because I'm still working through this issue and I know there will be someone behind me that finds this information useful.

I've completed the wiring of the bike and I have everything together. When I try and start the bike, it cranks with the occasional backfire through the carbs and what looks like whiteish smoke from exhaust. I've tested the spark plugs outside of the block and they are firing just fine. But, still no start. 

Here's the thing: You said to follow Revival's guide. In their guide they say "The easiest way to determine if you have a CDI is to look at your OEM wiring diagram and locate the kill switch.... When the kill switch is activated it completes a circuit that grounds out the CDI killing the ignition spark. In other words, if your Kill switch completes a ground circuit you have a CDI ignition. "

Referencing my wiring diagram (http://manuals.sohc4.net/cb650/technical_reference/WD650.jpg), it appears to me that my kill switch does not complete a ground circuit like they described.

Therefore, I wired the bike so that the wire the coming from IGNITION OUT on the M unit is spliced in with the b/w so that it gets 12v power like it did with the old harness. Like I said, I am getting spark to the plugs but the bike is not starting. Perhaps the spark at the plugs is not strong enough under compression due to me not wiring the spark units correctly?

I'd really like to hear you thoughts on this one calj737.

Sounds to me like the cylinders are firing at the wrong time-180 degrees out.

[caluser2000]

Yes, follow the CDI approach. Yes, the relay is my reference.

I'm going to revive this thread because I'm still working through this issue and I know there will be someone behind me that finds this information useful.

I've completed the wiring of the bike and I have everything together. When I try and start the bike, it cranks with the occasional backfire through the carbs and what looks like whiteish smoke from exhaust. I've tested the spark plugs outside of the block and they are firing just fine. But, still no start. 

Here's the thing: You said to follow Revival's guide. In their guide they say "The easiest way to determine if you have a CDI is to look at your OEM wiring diagram and locate the kill switch.... When the kill switch is activated it completes a circuit that grounds out the CDI killing the ignition spark. In other words, if your Kill switch completes a ground circuit you have a CDI ignition. "

Referencing my wiring diagram (http://manuals.sohc4.net/cb650/technical_reference/WD650.jpg), it appears to me that my kill switch does not complete a ground circuit like they described.

Therefore, I wired the bike so that the wire the coming from IGNITION OUT on the M unit is spliced in with the b/w so that it gets 12v power like it did with the old harness. Like I said, I am getting spark to the plugs but the bike is not starting. Perhaps the spark at the plugs is not strong enough under compression due to me not wiring the spark units correctly?

I'd really like to hear you thoughts on this one calj737.

Sounds to me like the cylinders are firing at the wrong time-180 degrees out.

Here's the catch: I didn't do ANY engine work. So, if it was running 3 months ago with the same stuff, how would it become 180 out of time? Here is a video of what it sounds like and also the exhaust:

Well you didn't mention that at the start for one. Are we to guess what work you have done previously?

Have you played around with any connections to the coils? Reversing the pairs can cause something similar to what you described.

[caluser2000]

Yes, follow the CDI approach. Yes, the relay is my reference.

I'm going to revive this thread because I'm still working through this issue and I know there will be someone behind me that finds this information useful.

I've completed the wiring of the bike and I have everything together. When I try and start the bike, it cranks with the occasional backfire through the carbs and what looks like whiteish smoke from exhaust. I've tested the spark plugs outside of the block and they are firing just fine. But, still no start. 

Here's the thing: You said to follow Revival's guide. In their guide they say "The easiest way to determine if you have a CDI is to look at your OEM wiring diagram and locate the kill switch.... When the kill switch is activated it completes a circuit that grounds out the CDI killing the ignition spark. In other words, if your Kill switch completes a ground circuit you have a CDI ignition. "

Referencing my wiring diagram (http://manuals.sohc4.net/cb650/technical_reference/WD650.jpg), it appears to me that my kill switch does not complete a ground circuit like they described.

Therefore, I wired the bike so that the wire the coming from IGNITION OUT on the M unit is spliced in with the b/w so that it gets 12v power like it did with the old harness. Like I said, I am getting spark to the plugs but the bike is not starting. Perhaps the spark at the plugs is not strong enough under compression due to me not wiring the spark units correctly?

I'd really like to hear you thoughts on this one calj737.

Sounds to me like the cylinders are firing at the wrong time-180 degrees out.

Here's the catch: I didn't do ANY engine work. So, if it was running 3 months ago with the same stuff, how would it become 180 out of time? Here is a video of what it sounds like and also the exhaust:

Well you didn't mention that at the start for one. Are we to guess what work you have done previously?

Have you played around with any connections to the coils? Reversing the pairs can cause something similar to what you described.

Just to keep the conversation relevant to the topic, I've made another topic about the issue we are talking through now. That topic can be found here: http://forums.sohc4.net/index.php/topic,186416.0.html

Copy your question over to that topic and I'll answer it in there.

Now that is damn funny

[caluser2000]

I'm really not trying to be annoying or commanding in any way. Sorry if it came off as such. I just don't want this thread, which is for an ignition-related issue, to be about something totally different. I'm trying to make it the least confusing for someone searching a similar problem.

Fair enough

[MichealAllen]

Hello all,

I'm in the process of installing a motogadget m-Unit Blue on my 81' CB650 Custom. However, it is not clear to me if the spark units from my old wiring system need to remain in the new system. Based on the research I've done, it looks like I can ditch them. Hopefully, someone with more knowledge than I can clarify if I need them in my new system.

Thank you for any and all information!

Hey thanks for starting this thread. The link you provided from revival does not seam to be available anymore. Did you finally get yours up and running? Thx
Allen

[randomguy81]

Which means a ground-activated KILL. Back to "CDI" wiring method.... 

AHHHHHHHH. It all makes sense now. I will wire it up the other way. Thank you so much for the help.

Did you get it running properly? I have a 81 cb650 with an m-unit but I’m only getting cylinders 1and4 running - 2 and 3 remain cold on the exhaust. Would greatly appreciate a wiring diagram to check what I have is correct as I’m running out of ideas

[scottly]

Which means a ground-activated KILL. Back to "CDI" wiring method.... 

AHHHHHHHH. It all makes sense now. I will wire it up the other way. Thank you so much for the help.

Did you get it running properly? I have a 81 cb650 with an m-unit but I’m only getting cylinders 1and4 running - 2 and 3 remain cold on the exhaust. Would greatly appreciate a wiring diagram to check what I have is correct as I’m running out of ideas

Read this thread: http://forums.sohc4.net/index.php/topic,186416.0.html