Need help with electrics please

[gbw]

I'm getting quite frustrated. Any suggestions?

77GS750B. Stock jet sizes, stock airbox, stock exhaust, Martek electronic ignition.

Could not get carbs sorted after complete dip and rebuild. Always rich.

Spark weak so cleaned/replaced connections and grounds and did the coil relay mod.

Spark still weak so replaced 30 yr old original coils, wires, and plug caps (with these coils/wires and NGK caps).

Spark still weak so tested charging system according to manual.

Test indicated regulator failure (less than 14V across battery...was actually 11.5).

Bought and installed duaneage r/r.

Test still indicates regulator failure...measures 12.5 across battery at 5k rpm.

Spark still weak.

Read that bad battery could muddy results. Topped off battery with distilled water and charged fully, same results of 12.5v across battery at 5k rpm.

Had battery tested. Test results were marginal. Bought new AGM battery for $70 + tax.

Still getting 12.5v across battery at 5k rpm. Spark still weak. Carbs still rich. Plugs still fowled. Getting 20 mpg. Feeling frustrated. Going broke.

Any suggestions? Think I'll go get a beer.

Could the Martek electronic ignition be the problem? I don't think the company even exists any more. I'm not even sure how to troubleshoot it.

At this point I may need counseling. I mean, I really like this bike but it is driving me FREAKIN crazy. How come I cant get it sorted out?

Any ideas are appreciated.

duaneage asked the following questions in a PM. Thought I should include them here:
1. possible bad battery, dead cell.
ans...new battery today

2. How are the ground connections on the RR as well as the battery?
ans...RR is mounted under the battery box in the holes from the old regulator. It is grounded to a bolt that holds it to the battery box. There is 0 resistance between the body of the RR and neg battery terminal. There is 0 resistance between the battery case the neg battery terminal.

3. Last, what were the stator voltage readings?
ans...80V AC between each of the three legs at 5k rpm...also, while I was testing just now two of the bullet connectors you provided slipped off the wires. Obviously I did not crimp them well. I didn't have any bullet connectors so I replaced all the connectors with new weatherproof spade connectors. Got the same 12.5v dc across the battery.

Thanks

[BassCliff]

Hi Mr. gbw,

Did you get a 6-wire unit from Mr. duaneage? Is the sense wire connected to a switched 12v source? Usually the rear brake light connection is used.


Thank you for your indulgence,

BassCliff

[duaneage]

It is connected or he would have 16 volts on it. A simple test would be to disconnect the black wire from the brake light switch and see if the regulator drives the voltage up. This is done in cars as well to test the charging system.

I think something is pulling the system down, could be an electrical problem with an accessory or a short circuit through a component somewhere.

Pull fuses for the headlight and other lights leaving the main fuse in (naturally that is required to test) and see if removing load increases the voltage. On my 650G I can switch off the lights to test no load charging.

Referring to the diagram below, measure voltage from the red wire off the RR to the green wire metal tab. Then unhook the red wire connector and see if the RR provides ample voltage without being connected to the bike or not.

[gbw]

Hi Mr. gbw,

Did you get a 6-wire unit from Mr. duaneage? Is the sense wire connected to a switched 12v source? Usually the rear brake light connection is used.


Thank you for your indulgence,

BassCliff

Thank you, yes. 6 wire unit. Black wires connected to the switched power to the rear brake switch. This wire shows the same 12.5v as the battery.

[gbw]

A simple test would be to disconnect the black wire from the brake light switch and see if the regulator drives the voltage up.

I will do this test in the morning and report the results

Pull fuses for the headlight and other lights leaving the main fuse in (naturally that is required to test) and see if removing load increases the voltage. On my 650G I can switch off the lights to test no load charging.

The 77 GS750 only has one fuse. Well, mine has three, but I added two of them. One for the coil relay mod and one for the battery tender. The 77 GS750 has an on/off light switch. Per the manuals, all these tests were conducted under no load...ie, the light switch in the off position.

Referring to the diagram below, measure voltage from the red wire off the RR to the green wire metal tab. Then unhook the red wire connector and see if the RR provides ample voltage without being connected to the bike or not.

I don't see a diagram. Am I missing something?

[TheCafeKid]

Ermm. What are your fuel screws set at (the ones on the bottom of the carbs?) What possition did you set your needles? AND, are those IN FACT 77 carbs? If not, this will skew basic settings a hair. Also, I have seen and heard people upjetting because their bike starts to run like crap when they dont adjust the valves. What were your jet sizes? do they conform with the jet sizes for the 1977 GS750 VM26SS carbs? There were a couple of differences between 77 and later model carbs.

[BassCliff]

I think Mr. TCK posted that to the wrong thread.

Are you talking about this diagram?




Thank you for your indulgence,

BassCliff

[TheCafeKid]

I think Mr. TCK posted that to the wrong thread.

Are you talking about this diagram?




Thank you for your indulgence,

BassCliff

No actually i didnt. If you RE Read his original post on this thread, he says he is having trouble with it CONSTANTLY running rich. I am not entirely certain his spark is entirely to blame. He may be having issues with weak spark, but this all stems back to being rich from the get go. I simply suggested he check his carburetion settup again.

BY THE WAY: I would eliminate any NON STOCK items from your equation, aside from the R/R. Ditch the ignition system, put the points and condensor back in, untill you are sure the ignition system is or isnt the problem. Chasing an ignition problem from an unknown/defunct company might well be a nightmare.

[BassCliff]

No actually i didnt. If you RE Read his original post on this thread, he says he is having trouble with it CONSTANTLY running rich.

Sorry. I guess amongst all the electrics talk, I overlooked both times Mr. gbw mentioned running rich. I bow to your carb expertise. And I'll make an appointment with the optometrist.


Thank you for your indulgence,

BassCliff

[J_C]

All this talk about regulators.... have you tested the stator? Need to make sure that's working too.

Also, check your battery leads. I had marginal charging, found a bunch of corrosion on the battery + and - wires. Replaced those and got a significantly better result!

[TheCafeKid]

Sorry. I guess amongst all the electrics talk, I overlooked both times Mr. gbw mentioned running rich. I bow to your carb expertise. And I'll make an appointment with the optometrist.


Thank you for your indulgence,

BassCliff

No expertise here, just happen to know there are slight but important differences in the 77 carbs from the later model VMs. Mainly, in the slide assembly, needles and needle JETS. (different sizes from later) Im not saying that his ignition isnt the problem, just curious how he set his carbs up when reassembled, and if they are stock to the bike. Thas all

[gbw]

Thank you for the questions. All this electrical stuff started because of the carbs. Actually I have not messed with them much since I installed the stock airbox and jets because I knew I'd be going thru the electrical anyway.

What are your fuel screws set at (the ones on the bottom of the carbs?)

1.5 turns out from bottom. Now, my #1 and #4 carb had stuck fuel screws which I got out during the carb rebuild. However, as part of the getting them out process I'm sure I changed the size of the jet hole a little. I'm sure I'll have to turn these screws in further at some point but was trying to get the electric sorted before I set the carbs.

What possition did you set your needles?

Center. I will probably move it down one notch next time I have the carbs off to eliminate what I think is a lean condition at WOT. Again, I've postponed my plug chops until I have strong spark.

AND, are those IN FACT 77 carbs? If not, this will skew basic settings a hair.

I believe they are stock. No way to really be sure I guess.

bike starts to run like crap when they dont adjust the valves.

Valves were adjusted a few hundred miles ago.

What were your jet sizes? do they conform with the jet sizes for the 1977 GS750 VM26SS carbs?

Got the jets from the rebuild kit. Main jet is 102 and Pilot jet is 15. Manual says stock are 100 and 15 so that should be pretty close. If I can't get the carbs dialed in once I have strong spark I'll drop back to 100s. These replaced 105 and 17.5 the PO used with the K&N pods.

Really appreciate your help.

[gbw]

Ditch the ignition system, put the points and condensor back in, untill you are sure the ignition system is or isnt the problem. Chasing an ignition problem from an unknown/defunct company might well be a nightmare.

I was afraid someone would suggest this. I was really trying keep my head in the sand on the electronic ignition. I mean, its electronic right...should last forever??? Wishful thinking. The PO installed this ignition and I don't have the original.

Now I have to find and buy a stock ignition. I can buy from Bike Bandit for $120 to $140 (I'm not sure if I have KD or ND. Anyone know how I can find out which?). Or I could buy a DynaS from Z1 for the same price. Of course if I buy a DynaS I would probably want to buy Dyna coils to replace the JC Whitney coils I'm running now so I guess that will double the price.

[gbw]

Thank you for replying and for the suggestions.

have you tested the stator?

.
I get 80V AC across each of the three generator leads at 5k rpm. What I've read leads to me believe this indicates a functioning stator. Do I need to troubleshoot the stator further?

Also, check your battery leads.

All the battery leads look good with no corrosion, but I will check them again this afternoon.

[gbw]

disconnect the black wire from the brake light switch and see if the regulator drives the voltage up.

Goes to 12.7v

measure voltage from the red wire off the RR to the green wire metal tab..

13.3v

Then unhook the red wire connector and see if the RR provides ample voltage without being connected to the bike or not.

126v