still have weak spark...now what???

[gbw]

From previous post I've been trying to sort out the weak spark situation on this bike. My question is that after all the things I've done below, I still have weak spark. What could possibly be left that I have not replaced? Why would the spark still be weak?

The following is a summary to date:

77GS750B. Stock jet sizes, stock airbox, stock exhaust, stock points/condenser ignition (thanks wazz for the 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.

TCK suggested that my Martek electronic ignition could be questionable and he is not the first cast doubt on this discontinued product.

Thanks to wazz I now have a good as new points and condenser igition...just installed. The bike starts and runs pretty good with the new ignition but I've not put a timing light on it yet.

Anyway, the spark still looks very weak. I'm getting pretty frustrated with this thing. What could possibly be left that I have not replaced? Why would the spark still be weak?

I feel like I need a strong spark so I can sort out the carbs. I really think this is the last thing I need to do to the bike this season. Hope I can get this sorted out before Fennimore...otherwise I'll have to rent a Harley for the trip! Now how would that look???

 

[Guest]

What's the volts at the coils with the coil mod? Maybe a bad relay?
What are you guaging the weak spark on? It's running good with the new ignition?

 

[lucabond]

You should be getting better than 12.5 at 5k. I'd start there, have you run the R/R direct to the battery ? And checked your engine ground and the cable running from the battery- to ground ? If your not getting the right voltage at the battery then there is less for the coils. Maybe it seems to run rich due to a poor spark, just thinking.
Good luck

 

[SqDancerLynn1]

Fix the charging first!! Did you check the stator ??. Big difference between 11 & 14 Volts
I DON'T think those are the right coils. Did you see the note NOT FOR 4 CYL Motorcycles

 

[TheCafeKid]

If the P&C ignition still didnt change anything... You gotta be bleeding juice somewheres. Or not making enough to begin with. Id also suggest looking at that charging system. Should get 12.5 at IDLE, and climb up to around 14 or better at 5k... (not more than 15.5 or there abouts or your Regulator is shot...)

 

[Guest]

Maybe it seems to run rich due to a poor spark, just thinking.

i'll second this!

___

definitely check your stator first. if thats ok and with the new battery the charging prob can only be due to the bad rr or poor electrical connections

though, 12.5V should be enough to give a decent spark (with the lights OFF)

measure the actual voltage at the coils

 

[rustybronco]

Check the complete charging system.

running rich...how is the air filter.
plugged, over oiled?
floats set correctly?

What are you guaging the weak spark on?

my thoughts also.

 

[RJ]

Go over your ground wire to frame connections and make sure they are shiny and spotless. Go over your connectors and make sure they're clean as well. I'm highly suspicous of any JC Whitney products. Reinstall your old coils or get a set of Dyna coils.

 

[gbw]

Thanks everyone for the overnight feedback! I'll take a look at all these suggestions today and let you know what I find. I tried to answer your questions as best I can. I'm very interested in how to test the stator more/differently than I have.

What's the volts at the coils with the coil mod? Maybe a bad relay?

I'll measure this today and let you know.

What are you guaging the weak spark on? It's running good with the new ignition?

A take a plug out of the cylinder and ground it against the engine then start the bike. I get a few little light blue threads of spark across the gap. I expect to get a big, bold, blue spark across the gap.

You should be getting better than 12.5 at 5k. I'd start there, have you run the R/R direct to the battery ?

Duanage does not recommend connecting the r/r directly to the battery, so I have not done that.

And checked your engine ground and the cable running from the battery- to ground ? If your not getting the right voltage at the battery then there is less for the coils.

Yes. The wires look good and the connections are clean. There is little/no resistance between the neg battery terminal and the frame or crankcase.

Maybe it seems to run rich due to a poor spark, just thinking.

This is what I think. In fact, I think all the carb stuff I've done has been a waste of time and money and that I should have started with the weak spark and electrical system first. The reason I did not is that the bike always starts even when it is not on the charger and it seems to run ok to me, but I bet someone with more experience would think the bike is sluggish.

Fix the charging first!! Did you check the stator ??.

Well, it generates 80V ac between each of the legs, and has continuity between each leg, but has no continuity to ground. I have not actually looked at it, but I understood that if it passed these three tests it was good. Is there something else I should check?

I DON'T think those are the right coils. Did you see the note NOT FOR 4 CYL Motorcycles

I saw that, but I know someone else who is running these on a GS850GL and he gets good spark. I will probably go back to the stock coils b/c now I don't think they are at fault.

definitely check your stator first. if thats ok and with the new battery the charging prob can only be due to the bad rr or poor electrical connections

Any suggestions on how to check the stator? The r/r is new and duanage actually sent me a second one to verify. It is possible that I missed some connections.

measure the actual voltage at the coils

I'll check this today

Check the complete charging system.

I've followed the instruction in Clymers and the Stator Papers. Is there something else?

running rich...how is the air filter.
plugged, over oiled?
floats set correctly?

The air filter is clean and lightly oiled. The floats are set correctly.

 

[Planecrazy]

NONE of the coils are the problem for now - I reiterate what others have already said ... if you're only getting 12.5 volts at 5K you have a charging system issue. Even with the bike switched off your "good" battery should read better than 12V, so it sounds like the charging system "isn't," and if it isn't providing a healthy charge than nothing you do to the ignition system is going to improve the spark - sounds like there wasn't a problem there to begin with. The R/R should be putting out better than 13V at almost any rpm if it is working properly and if the stator is generating properly.

Also, I agree that you need to triple check the ground connections to make sure the system is properly grounded. Once you've done this and run through the Stator / R/R tests you'll find the problem or verify proper operation.

Good Luck!

 

[gbw]

Also, I agree that you need to triple check the ground connections to make sure the system is properly grounded. Once you've done this and run through the Stator / R/R tests you'll find the problem or verify proper operation.

Thanks Steve. I feel like I've done this but maybe I missed something or didn't do something well. I'll go over it again. I've been toying with the idea of opening the stator case to look inside and see what is what, but since it tested well I didn't think I'd have to do that. Guess I'll need a new gasket to do that.

 

[TheCafeKid]

gbw my good sir, if the bike isnt charging at the above stated numbers, then the charging system is at fault somewhere. Thankfully, there isnt much to em, only really three (or two) parts that can be the culprit, unless its the wiring itself. If the stator tests out good, the R/R tests out good, then its the connections or grounds, or you got screwed on a battery.

 

[gbw]

gbw my good sir, if the bike isnt charging at the above stated numbers, then the charging system is at fault somewhere. Thankfully, there isnt much to em, only really three (or two) parts that can be the culprit, unless its the wiring itself. If the stator tests out good, the R/R tests out good, then its the connections or grounds, or you got screwed on a battery.

Thanks for that. Somehow that makes me feel better. I've replaced everything except the stator so I'll go over all the connects and grounds again later today.

 

[rustybronco]

Thanks to wazz I now have a good as new points and condenser ignition...just installed. The bike starts and runs pretty good with the new ignition but I've not put a timing light on it yet.

I assume you static timed it?
it should be within a few degrees if you did it correctly.

I've followed the instruction in Clymers and the Stator Papers. Is there something else?

no.
I needed to know what voltage the stator was putting out, you answered that

Well, it generates 80V ac between each of the legs, and has continuity between each leg, but has no continuity to ground

 

[Guest]

not sure this would help but you seem to be doing all the right things, so you'll get there eventually

your stator indeed sounds healthy

 

[SqDancerLynn1]

Do you have the correct NGK B8ES plugs ? gapped at .023

 

[gbw]

Do you have the correct NGK B8ES plugs ? gapped at .023

Yes sir, and they are comfortably nestled in new NGK plug covers.

 

[trippivot]

what is the unloaded AC output of the stator? are all 3 legs even?

what color is the spark you do have? orange, yellow, white, or blue?

I'm sorry but I have doubts on the quality of the information you have given us here for diagnosis. things are not adding up to me.

weak spark is common with bad points and a bad capacitor.

but electronic ignition is a very different story.