Topic: Charging System help!

[bjonesin]

Hey Everyone,

I have lurked on this forum for several months, while I saved up enough money and earned my license. I have a 77 CB750, and it's having some problems. I am the 3rd or 4th owner of this bike and to say its been neglected is an understatement. The first time I rode it was to have it inspected to have it tagged 4 days ago. I went out to turn it on today and the headlight goes dim within 30 seconds after starting it. It seems to die when this happens and won't run properly. I can only get it to start by kickstarting it, the electric start only buzzes. Since this is my first motorcycle I'm kind of at a loss for what to do. Is it not starting because of dirty carbs or the charging system on it is bad? Maybe a bad coil? I was told by the PO that replacing the starter wasn't a bad idea. So you all are smarter than I am, what's going on with my bike?

[bjonesin]

I know everyone likes pictures

[Plummer]

Clean your fuses and holders with some fine grit sandpaper , and put a little dielectric grease on them , mine did the same thing . If that doesn't help , get a manual and start chasing the problem .

[LesterPiglet]

It's electric problem not fuel. Don't change the starter, test it removed from the bike. If you had a coil problem it would affect 2 cylinders as each coil feeds 2 pots. Do as Plummer says and take it from there.

[Patrick]

The good news is if your new bike made it to the inspection station and back, it sounds like your engine is runable.

The bad news is I hope you are comfortable working on old bikes, cuz you are going to have to.

You bike loses juice as you ride it likely because it is not charging correctly. You are essentially running on the battery, not the alternator. Ride it long enough and it will stop. This could be as simple as a corroded negative battery cable connection to or it could be a series of connections that corroded from its time as lawn art. Clean your battery cable connections until they are shiny. Then, start the bike and put a mutltimeter between the positive and negative battery connections as the bike is running. Rev the engine to 3,000 rpm and hold it. What voltage are you reading? It should approximate 14.5 volts. If it is less than than you probably will need to clean all the wiring connections. Trace the wires. Clean. Test again.

If, after that, the bike still is not charging correctly, check back here and tell us what you have done and we can be of more assistance.

Before you do anything, though. Get a service manual.

Patrick

[grcamna2]

Get a little syringe battery hydrometer(a small tube w/ a bulb up top w/ 5 little colored balls inside)and test each cell individually on you're battery...it may have a weak or dead cell or 2 and you can then replace it and continue your tests.

[madmtnmotors]

Get a little syringe battery hydrometer(a small tube w/ a bulb up top w/ 5 little colored balls inside)and test each cell individually on you're battery...it may have a weak or dead cell or 2 and you can then replace it and continue your tests.

grcamna has the best suggestion for the first item to assess. The charging systems on these bikes will not function if your battery is failing. The magnetic field is created by an electro-magnet (field coil) that relies on a good 12 volt source. A weak battery will not drive the alternator. Newer charging systems use a permanent magnet and are not suceptible to this malady. So determine the condition of the battery first, before moving on to the next item.

[bjonesin]

Thanks for the suggestions. I don't think its a dead cell in the battery since it's less than a week old. I will start there and work through every one of the suggestions here. When I get stuck, or have results I will post. Here goes nothing!

[grcamna2]

I recommend that you charge you're battery up to max before you begin any tests...use a charger w/  1-1.5 amps constant output..NO Higher or you'll cook your battery.Then to check it you can use the mini hydrometer to test all the cells and see if all the little balls are floating evenly in every cell,then install the battery and test the system.

[bjonesin]

Well, I got her running after working on it all afternoon! I checked the battery at autzone, and cleaned the fuse holders with sand paper. That's the picture I provided.  My wiring looks like its a mess. After getting it to run intermittently, I was looking for causes that were suggested. I figured the next bet was the coils and only way I knew how to check the coils without taking them off was to feel the header. After one side being ice cold, I regapped and cleaned the spark plugs and reinstalled.Turns out that was the problem. I ran it around the neighborhood to make sure it worked.

Thanks for all the input and help!