74 cb125s frustrations...

[bamajoe]

I guess I need some help brainstorming...

My cb125 will not run..
Backstory.. I bought this bike, cleaned the carb and it ran. I rode around a little bit than tore it down to chop it (it wasn't good enough condition to restore or anything like that) well that project drug out about 2 yrs like projects tend to do.. Now it's time to get it running.. Cleaned rebuilt carb, cleaned points again. Fired it up! Ran but felt like it needed some jetting due to exhaust and intake changes. Rode it about a mile.. Worse and worse... Pushed it back to the house. Checked battery, dead. Checked my wire found the charge wire loose. Fixed that, charged the battery. Will not run or even hit... Rechecked points, a little out, adjusted. Verified fire. Good. Got fuel. Checked valves, perfect. Carb perfect all jets clear. Getting plenty of fuel. Kick kick kick... Nothing. Check plug again, wet. Clean it. Check fire against, good. Won't hit.
What am I missing????

 

[lucaspa]

That sucks, I ran into similar issue with my 75 CB125. Sounds dumb but your ignition is on and switched to run right? I have to check as I spent 15 minutes trying to kick over a bike because of this. Also, I had a battery that died and showed good after charging but it was not alive enough to hold charge or provide enough current to start bike. So if you have a spare battery I would check this first, just swap them out. Next I would check volts on battery and take out plug ground against engine and kick to make sure you are getting a strong spark. Also, check the voltage drop over your harness as you may have a shit ground or harness that needs some love. Third, do you have a clear fuel line from tank to carb? I ask as if the petcock or gas cap are plugged you may have gas in tank and line but it may not be getting to your carb. The vent hole on the gas cap can get plugged from rust. So get a PVC pipe and two caps, drill a hole in one thread a fitting into it and make yourself a temp gas tank. This will help eliminate fuel line issues. That's all I got so I wish you luck man.

 

[Big R]

Once everything cools down, check for spark again. Old ignition coils heat up and fail, but then work after cooling down.

 

[bamajoe]

I've pulled the plug and yes it's got spark. The battery reads 6.2v probably could be a little higher but I AM getting spark. I've got clear fuel line and yes fuel flowing good and the plug is wet after I kick it several times, so I'm defiantly getting fuel up thru the carb.
I'll charge the battery again, spark might not be hot enough.

 

[bamajoe]

Alright so I finally got around to getting a new battery in and it fires right up! Barely charging tho which is probably due to my unfinished sketchy wiring . It seems that if the battery doesn't have 6.5 or more volts IT WILL NOT START! it'll have spark but won't hit at all... O well.. I guess it's picky.. Are these bikes known for that?
Here's a little vid..
http://youtu.be/TCc-_XrWebI