1979 CB750L Runs horrible and wont charge

Emarcottesr

CB750 Member
Messages
21
Reaction score
4
Points
3
Location
Zarathustra1$
So I traded a couple jet skis to my brother in law for a 1979 CB750L he had recently gotten. He said it just needed some carb work cause they leaked but said he took it for a test run to the end of his block and back and it runs fine other than the leaking carbs. Well after rebuilding the carbs and soldering the cracked overflow stem in carb #2 I did a bench sync and put it all back together. The tank was full of sludge and I'm not kidding a hairball even came out. (don't ask me). It fires right up barely needs to have the choke on it seems great I go to give it gas and the missing and backfiring and overall struggle cries start. So I replace ignition coils. First had them wired in backward (positive to negative and vice versa) surprisingly it ran ok not great but ok. So I checked the timing and during that process found out what I did and fixed it as well as got the timing dialed in. Now the bike is running pretty damn well so I figured ill run up to the store on it. After about 1.5 miles the bike started to run like shit. Didn't want to go above 40moh and anything past about a quarter turn on the throttle was met with a dying motor. I pulled over waited ten minutes and it fired up ran pretty good got up to about 95mph for a sec but almost home and it happened again. This time battery was totally dead so after walking it a couple blocks I push started it and had to keep the choke on to make it the rest of the way. So I looked into the charging system and found that one of the brushes was jammed so I cleaned it all up got it free and back to working condition put it all back together and soon as I turned on the ignition the 10 amp fuse that runs across the starter solenoid blew. I tried again blew another one. Replaced said fuse with a 25 amp and figured fuck it the solenoid says 30 amp on it so I should be safe up to 30. That fuse didn't blow and the bike ran great. The charging system was working and i figured good to go. NOPE. I rode a loop around the neighborhood and after about 3 miles it all went back to shit. The charging system isn't working the engine feels and sounds like its missing it idles like dog shit I just don't know what the hell is wrong.
 
Sounds like you need to empty the bowls. Might have gotten something in there and the agitation of the bike will eventually send it to the jets. When you shut the bike off, it settles to the bottom of the bowl again, allowing it to start and run... until it gets back to the jets.
 
I should probably pull the carb bank off and check the jets too. Thanks for the advice. Any idea why the charging system is being hit or miss? I've checked the wires they have no damage. I barely understand how to work my voltage meter I got the expensive one so I think they expect a pro
Fix the charging issue. The ignition needs electricity to work. A battery discharged to 11 volts may not even run an engine at all.
i was told that an engine could run without a battery
 
Not exactly. This bike at idle will drain the battery faster than the charging system can replenish it. It isn't a modern car charging system. These old charging systems go bad for a variety of reasons (carbon build up, brushes wear down, wires become brittle, R/Rs fail) so don't be too surprised it needs attention.
 
Back
Top