CB100 6 volt to 12 volt conversion, almost there! HELP!

zimfistofdoom

New Member
So here is what I have replaced so far in converting my 1972 CB100 to 12 Volts:
-stator
-regulator/rectifier
-ignition coil
-capacitor (Kickstart, replaces battery)
-bulbs and whatnot to match the 12 volt system

Here is the problem:
I can get it to kick over and start, but the idle is very low and as soon as I start rolling on the throttle it stalls out. Before the conversion it ran fine, started on the first kick and ran like a champ. I'm undergoing this project so I can have a headlight that is useful at night....


I tried adjusting the carb, but that seems to be to no avail. My initial thoughts are timing adjustment, tappet adjustment or spark plug gap, but I would like a little insight before I do any damage.

Has anyone out there done this conversion or something similar? Any and all information would be greatly appreciated. I haven't been able to find a definitive guide for how to do this conversion, so I plan to put one together (once I am successful in the swap....)
 
Looking forward for some response on your thread. I am going to be doing the same thing with my CB100.


It does not have a battery right now and has similar issues.
 
Done the conversion and so far im am successful. CB125
12v stator
12v rectifier
12v regulator
12v headlight and bulbs
12v battery
i used the 6v coil and wired in two 1 ohm resistors to bring the resistance up to what a 12v would be.


So far it runs fine and charges. Before it put in the resistors it ran real good. After i put in the resistors i had to fuss with the carbs a bit. I think the hotter spark was compensating for the carb setting. Now if your not running a battery your spark may be even weaker because at idle its only running of what the bike can provide. I would do all the the tune up stuff, valves, spark gap, point gap and timing. See if that helps. Then i might consider adding a battery. Just to see if that is the problem. THis may not help but is pretty cool. Pamco Ignition. http://www.cb750ignition.com/ I have one on my 6v CL125 but it works on a 12v conversion as long as you are using a 12v coil or the resistors like mine.
 
You can run 12v blinkers. And 12v headlights are a little brighter. Not much advantage for the amount of work required.
 
In progress update:
I opened up the carb to see if it could be clogged. Found some particles but everything seemed to be flowing properly. Turns out the float level was waaaay off, correcting that and retarding the timing made for much better idling. It has also ceased stalling upon throttle, but is still backfiring and sounds like it is only firing every other stroke. I'm going to try jetting it once the new jets come in, I do have a Uni pod filter on it which may explain the backfiring and lack of power. Will update when I try something else!
 
Any luck? I'm going through the process of trying to get my cb100 after swapping it over to 12v and am having trouble getting spark. Out of curiosity what coil did you end up going with?
 
With the stock coil and the 12 volt you will get a bigger spark but it will shorten the life of your points. I'm running a few resistors to bring the resistance to the right amount
 
Ahh gotcha, my stock coil died on me before the change over so I'm trying to get 12v coil from JC whitney to work. It seems my condenser is bad as well so now I'm waiting on a new one to come in.


-Thanks,
Zach
 
find out what the resistance of the coil your getting is. i think a stock 12v coil for a honda was about 5ohms
 
Hrmm looks like this one is 3.5 primary and 10.8 Kohms secondary. I don't have a decent multi-meter on-hand today, but I'll check the actual unit as soon as I can. Would a lower primary resistance have an adverse effect on getting spark? I would think only a higher resistance would cause a weaker spark and lower shouldn't harm anything, am I wrong in that?

-Thanks,
Zach

Edit:
Just found the nice one (read: the one that actually works) and it read 5.4-5.5 primary and 10.3 Kohms on the secondary. Hopefully that's within the acceptable range. For future reference though am curious about what a coil with the wrong resistance can cause if anyone knows.
 
The lower resistance the stronger spark but the more there is running through the points and shortening their life.
 
Cool, that's what I figured was the case. Thanks for clarifying! I'll post up my build as soon as it's running!
 
I read about the hondaman ignition setups that help the point life considerably.. wondering if there is a setup for the 100/125s
 
There are 2 options. 1 is the hondaman. He does make them for the singles but they are not any cheaper then the one for a 4 cylinder. I have one for my 550. The other option is a PAMCO ign. I have one of those on my CL125s. Both will work on a 12 or 6 volt but still require the correct resistance or you will fry the unit. Increasing the resistance is as easy as buying two 1ohm resistors at radio shack and wiring them in before the coil. It cost less then $5 im sure,
IMAG0308.jpg
 
Hi gents!
I see 12v conversions must be common. I have a 1981 CB125s (stock bike with 6v electrical) that I want to convert to 12v so I can use 12v lights.
My bike has CDI. I am not sure what all I need to swap out on it for the conversion. I am guessing some years of bikes might require changing different things?
 

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