Electrical Short Question

[CrazyCloud]

I have done a lot of work to my '78 GS750 over fall and winter. Finally took her out for a short shakedown spin today. All was going great on the drive out. As I pulled off the road to turn around the bike died. Main fuse was blown. Replaced, bike started, go a few feet, dies again. Repeat with new fuse, dies again. The only electrical things I have done are wire in the brake signal wires to a new front master cylinder and put in new spark plug caps. Looking at it now it the 2 wires to the brake switch have uninsulated spots near the ends that may have touched. Could this have blown the fuse? It seems like it would have just made the brake light come on. I am severely electrically challenged, so please respond as if you are speaking to an 8 year old kid. If that wouldn't cause it, I'll start the wild goose chase...
Thanks guys!

[posplayr]

Do a search; you are not the first. I distinctly rember posting a step by step short detection process. Basically divide and conquer process of elimination. Engage brain now.

[CrazyCloud]

I was mostly just making sure there was no way the 2 brake signal wires touching can cause a short. I know the switch completes the circuit between the two wires, I just wasn't sure if the wires themselves touching could be a short. I don't think its the problem, but I would hate to overlook it out of being afraid to ask a question. I am not afraid to use my brain or search, just asking for feedback on one possibility for the problem. Thanks

[posplayr]

Your asking for the silver bulit answer when there is no simple way around a process of elimination unless you get lucky and find it early.

[GSCafe]

You are probably looking for a short to ground. Since you did make an electrical change, you might start your search there. Of the shorts I have experienced, one was inside a rubber booted connector. Maybe water got in there, I dunno. I found it by pulling and reconnecting each connector searching for the issue. I redid the connectors and put insulation on them. The other was a fray in the hot side of the taillight wire that touched the frame. Best of luck. I hope your short is obvious enough to make your search easy.

[CrazyCloud]

OK, thanks guys. I think I will clean/insulate each connection as I go, as has been suggested, and go through the whole bike. Looks like I will be spending some quality time with posplayr's GS charging health link and BassCliffs electrical odds and ends this weekend. I am very grateful to have all of the great information found here. I intended the bike to be a mechanical education, and it has lived up to that for sure!

[posplayr]

OK, thanks guys. I think I will clean/insulate each connection as I go, as has been suggested, and go through the whole bike. Looks like I will be spending some quality time with posplayr's GS charging health link and BassCliffs electrical odds and ends this weekend. I am very grateful to have all of the great information found here. I intended the bike to be a mechanical education, and it has lived up to that for sure!

I think you should get back to a running bike before you start tearing into everything. Your bike was running and now you have electrical cutout (i.e. no lights, no starter cranking) and apparently something that is blowing your main fuse. Solve this first; it will be easier for you to keep focused).

Step #1 Solve the blowing Main First:
Pull all of your fuses except the main fuse. Turn on the Key, see if the main fuse blows?
1a.)If it does, it is probably your R/R; disconnect the R/R and turn on the key without starting.
If the lights come on without the R/R connected then the R/R probably has a internal short. (you can test with an ohm meter to confirm)
1b.)If it does NOT blow the fuse then start inserting fuses one at a time till with the key on the Main fuse blows.
When you have a fuse that when inserted is blowing your main you know that circuit is causing the short.

In step #1 you should have figured out what is causing the main fuse to stop blowing.

Step #2 Figure out why the bike will not start.
2a) Turn on the key, do you have lights (yes this is what you fixed in step #1 above)
2b.) When you turn on the kill switch to RUN and push the start button does the motor crank?: If NOT check the voltage to Y/G wire to the solenoid
It should have +12V on it when you PRESS START (with Ign on and Kill on and Clucth pulled unless you disable clutch interlock)
2c.) If you have voltage then your Solenoid may be what "popped" and is bad. You can usually take these apart and clean if not get a lawnmower replacement from Lowes.
2d.) Once the bike is cranking again it should start (you said it was running before this problem started).

Step #3 Check your charging using the "Quick Test" (make sure the battery is good)
3a) Report the results here so we have a baseline and can diagnose the readings.
3b.) You will probably be instructed to follow troubleshooting based on these results.
One we confirm your parts are good, then you should be OK to start generally cleaning and reconfiguration of the wiring as per "GS Charging Health".
3c.) Follow the instructions in the GS Charging Health steps #1 and #2 for cleanup of connections and the grounding, and then the revised stator pages. But if you do step 3a above we can help direct you through the revised stator pages.
3d.) Strongly consider getting a SERIES SH-775 is yours is bad or you have a bigger bike.

Buy a can of DeOxit or the similar product that they have at Radio Shack. If you can't get that then get dialectic grease, but the spray is much easier to use. The DeOxit product, eats away corrosion and leaves a non corroding barrier on the metal that is still super conductive. For very dirty conenctiosn use Naval jelly of similar acid to get rid of the big stuff, flush with water the apply DeOxit.

[CrazyCloud]

That is a huge help. Just what I needed prioritize my efforts; I think you just saved me several hours of chasing my own tail.

[Gambit]

While I am a brand new member and not at all motorcycle inclined, that fuse will blow for only one very broad reason. There is a short of the hot wire to ground before it gets to where it is supposed to go. A crude way to describe it is the + or hot side of the battery is the top of a mountain, and the - or ground is the bottom of the mountain. Your electricity or current is like a river. All the river ever wants to do is get to the bottom. There is a dam in the middle of the mountain that is your component like lights or whatever. Without this dam, the river moves in a dangerous way. Your current, or river is bypassing whatever component it is supposed to hit and going to ground. Imagine the fuse as a wall at the bottom of the mountain protecting a village. By not hitting any obstacles, the river moves too fast and blows the fuse or hits that wall.

Sorry if this didn't help you. It is an odd way to understand electricity, but it's how I was taught many many years ago.

Basically, you have a short to ground before the voltage gets to do whatever it was supposed to do. Where is it? Dunno. Could be any hot wire. Basically, inspect your wires coming from your battery all the way to wherever they are going. Unplug and replug everything that you can think that may have been even temporarily disconnected or nudged or sneezed on while you were conducting your maintenance. Do not just keep replacing the fuse. A couple times is acceptable (as posted in the trouble shooting below) 5 is a good limit. Once you blow 5 of the same fuse, stop before you set the bike on fire. There is a serious problem that needs a proper resolution. Find it. Be sure. Fix it. Drive on.

[CrazyCloud]

Thanks Gambit, that does help. Pos, looks like my bike only has a main fuse, there is not a fuse box(1978). Looks like I will be unplugging connections instead of fuses to complete step 1 above. I'm picking up some fuses today so I can have a good main for the testing.

[posplayr]

I'm guessing you also have the separate r
ectifier and regulator. Take a stab in the dark and disconnect the regulator. That could easily be where your short is. Don't run the bike that way. If the short goes away then you need to change the the two r and r units. Then question is are you going to leave the bike electrical stock or do you anticipate changes like led lights? A simple solution to stay stock is get the Honda r/r from duanage. Otherwise the sh775. Read about these in gs stator in my links.

[CrazyCloud]

Quick test results:
Key off =12.8. Key on & lights 10 sec = 12.15. Idle @1500rpm = all over... 13.4 to 13.7, 13.8, back down. 2500 rpm = 13.43. 5000rpm = 13.7. Key off = 13.15. Suggests bad regulator?

Put a new fuse in to do quick test, started, idled, rev'd fine. Took for a spin after the test & it popped the fuse again after a few mins on road. I realize battery with load tested weak, it was new in August & trickle charged a few hrs last night. Was 12.4V before charge.

[posplayr]

Quick test results:
Key off =12.8. Key on & lights 10 sec = 12.15. Idle @1500rpm = all over... 13.4 to 13.7, 13.8, back down. 2500 rpm = 13.43. 5000rpm = 13.7. Key off = 13.15.

Put a new fuse in to do quick test, started, idled, rev'd fine. Took for a spin after the test & it popped the fuse again after a few mins on road. Possible bad regulator? I realize battery with load tested weak, it was new in August & trickle charged a few hrs last night. Was 12.4V before charge.

Based on the Quick Tests results:

• the battery is fine and is pretty well charged. Anytime you can set with lights and ignition on, bike not running at over 12.0V you are good. 12.2V is about as high as I have seen.
• The bike is charging but not quite up to where it should be. Could be dirty grounds. If you clean that up then the voltages should rise. You can test for dirty connections in revised Phase A tests. You do it at 5000 RPM, however you need to deal with the main fuse blowing first.
• Find out what is causing you to blow a main.

1. [*=2]First make sure you are using a 15 amps fuse.
   [*=2]If it is a 15 amp fuse switch to a 20 amp to make sure it is not something just barely pushing you over the top.
   [*=2]Check the wiring for evidence of additional accessories or other wiring magic. Is the bike electrical stock?
   [*=2]From what you are measuring I doubt it is the R/R but it is possible it is intermittent.
   [*=2]Is this a split R/R?

[CrazyCloud]

All electric so far looks stock. Yes r/r is separate units. I did try a 20 amp fuse, it blew too. I did clean up the grounds already, will check connections too. Will proceed with solving blowing main...

[posplayr]

All electric so far looks stock. Yes r/r is separate units. I did try a 20 amp fuse, it blew too. I did clean up the grounds already, will check connections too. Will proceed with solving blowing main...

I would replace the Separate R/R at this point. The old style R/R is nothing but bad news and unless you have a bare wire somewhere, it is probably the R/R. doing it.