81-550T, R/R tested good, but?

[Buffalo Bill]

I noticed that the bike will stall out during idle if I have the headlight on, but runs on with the light switched off. That's a 55 watt load.

My 81 550T is all stock and I replaced the Stator recently.
The R/R looks as old as the bike, but it tests out good, and I see 15V on my multimeter when the RPMs get over 4000. However the battery does not seem to be charging well and looses power over time.

Should the R/R be replaced, or any other reason why the headlight load would stall the bike?
Thanks. Bill

 

[Nessism]

Sounds like you have a bad battery if it looses power over time on a system providing 15V. Headlight load causing stalling could be bad battery related as well. I doubt the R/R is the problem.

 

[Buffalo Bill]

New battery?

New battery?

Sounds like you have a bad battery if it looses power over time on a system providing 15V. Headlight load causing stalling could be bad battery related as well. I doubt the R/R is the problem.

I should have said, the battery is brand new. The previous battery lasted only 18 months.
Bill

 

[Texas Don]

It's easy enough to have your battery checked. Any of the big box auto supply outlets and a lot of independent ones will test your battery for free. It seems logical that your battery should be good since it is new but, I've had 1 new battery fail almost immediately so it's not unheard of. Before you replace any part though, you should be able to condemn it on the basis of repeatable testing. If the battery tests okay and the stator output is okay, that only leaves the R/R unit or a wiring issue. Did you test the headlight switch, wiring and headlight plug for shorts, opens and grounds? If all of that checks okay then I would zero in on the R/R unit. Can you post your testing results for us?

 

[tom203]

New to you stator- did you do quick stator test to confirm its output? What voltage do you get at 2000 rpm? Maybe your connection from r/r to battery is weak, so battery is not getting that 15 volts at 4k- at idle with headlight on, things would be worse, but it shouldn't stall out, unless voltage to coils is really weak at low rpms.

 

[Graham]

Sounds like a short in the headlight circuit. If you are getting 15V @ 4000rpm then all seems well on charging.

 

[Buffalo Bill]

I think so too.

I think so too.

Sounds like a short in the headlight circuit. If you are getting 15V @ 4000rpm then all seems well on charging.

I think so too. A short or a drain somewhere in the headlight circuit.
Thanks. Bill

 

[Nessism]

Checking voltage at the coils would be the first thing I'd do. If it's less than 10.5 volts or so the coil-relay mod is in order.

Oh, and while you are checking out the charging system, did you remove the out and back stator wire loop to the hand control switch? If not, I suggest you do so before you cook the harness.

 

[Buffalo Bill]

Please don't imply, make yourself clear?

Please don't imply, make yourself clear?

Oh, and while you are checking out the charging system, did you remove the out and back stator wire loop to the hand control switch? If not, I suggest you do so before you cook the harness.

Ed, could you elaborate on this a bit. This would be good place to share an anecdotal experience.
Bill

 

[Nessism]

Ed, could you elaborate on this a bit. This would be good place to share an anecdotal experience.
Bill

Bill,

The archives has lots of information on this topic. Read this thread... http://www.thegsresources.com/_forum/showthread.php?t=165499

 

[Buffalo Bill]

Interesting, but knee jerk fix?

Interesting, but knee jerk fix?

Thanks for a tip on the weak wiring.
But I think our guys are wrong to disrespect the factory engineers, who had a good reason for sending one of the stator leads to the headlight: to protect the R/R from too much wattage and failure, which happens quite often.
After those DIY's do their direct wiring mods they risk burning out the R/R.
The factory thought to protect the R/R from overload in case the headlamp was switched off, burned out, or was unplugged.
Thanks for the link Ed.
Bill

 

[Nessism]

Thanks for a tip on the weak wiring.
But I think our guys are wrong to disrespect the factory engineers, who had a good reason for sending one of the stator leads to the headlight: to protect the R/R from too much wattage and failure, which happens quite often.
After those DIY's do their direct wiring mods they risk burning out the R/R.
The factory thought to protect the R/R from overload in case the headlamp was switched off, burned out, or was unplugged.
Thanks for the link Ed.
Bill

Bill,

That out and back leg is for bikes with a head lamp switch, which was outlawed in the US before your bike was made. The extra length of wiring serves no purpose, often overheats, adds resistance, and can destroy your entire wire harness if the heat is great enough. I strongly advocate removing the extra wiring before it's too late on all GS bikes, other than maybe the early bikes with the switch.

 

[koolaid_kid]

I have to agree with Ed. The engineers left that in the U.S. model because it is cheaper to have one world-wide harness rather than two harnesses that are market specific. Cost is the only reason, both the recurring costs of producing and tracking two harnesses and the one-time cost of engineering a different harness. As an engineer, I have to constantly look out for the bean counters, and this was clearly a cost decison.
When I pulled my harness out of my headlight this summer after my stator roasted itself, the connector was so melted I had to cut it out completely; nothing was salvageable. Since I cannot turn my headlight off I ran all 3 stator wires straight to the R/R and all is well. No functionality was lost; I checked and double-checked.
Please note, you do not have to remove the wires themselves, merely disconnect them from the stator output and R/R input.

 

[Nessism]

Please note, you do not have to remove the wires themselves, merely disconnect them from the stator output and R/R input.

Good point! Forgot to mention this. Eliminate the wire from the circuit, but it's not necessary to remove the wire physically. It's actually quite useful to leave the wire and use it for the coil relay mod.

 

[Buffalo Bill]

Good reasons from the kid?

Good reasons from the kid?

Thanks for the more reasoned answers, but Ed my bike has that headlight switch on the left hand control.
I'm going to take a deep look at the wiring after these clues, but not today, it's cold!
But, one last question please: That 3rd yellow stator wire connects to a W/G wire running to the headlight switch.
I should disconnect that yellow and connect it to what color wire in order for it to run into the R/R?
Thanks! Bill

 

[bwringer]

But, one last question please: That 3rd yellow stator wire connects to a W/G wire running to the headlight switch.
I should disconnect that yellow and connect it to what color wire in order for it to run into the R/R?
Thanks! Bill

The white/red wire.

 

[Buffalo Bill]

Just tried that, thanks?

Just tried that, thanks?

Thanks Brian,
I just came in from the garage and tried that, and ran the engine too.
I had a look at the wiring diagram and came up with the W/R wire, but is it really that simple?
I ran the bike up the highway and back, pulled up to my garage and the bike held a fast idle then came down to 1100-1500 rpm. There still is a load when the headlight is on and the idle slows, but I take that for normal.

It all gets back to this bike's frustrating problem: after it's well warmed up from some riding, it won't hold an idle below 2200rpm with out stalling out.
By trying to fix this problem, I've really improved every other aspect of it's running, but it just won't fix.
Things I've done:
Tried the coil mod trick (bummer, returned it back again).
Replaced the coils with some from a 97 Bandit 1200.
Replaced the piston rings.
Changed out the main jets for some slightly bigger ones, (makes great top end power now).
Changed the pilot jets with some slightly larger.
Replaced all the intake pipes.
New battery.
Replaced the plugs.

 

[Nessism]

Wonder if it's sucking false air past the throttle butterfly valve shafts? Something is wrong if it won't idle properly.

Where are the pilot/mixture screws set and have you vacuum synced the carbs? My old 550T was dead stock and the idle would hang until the pilot/mixture screws were opened up to 3.5 turns.

 

[Buffalo Bill]

Ed????

Ed????

Ed, you're one of the few 550 owners who respond to questions, could your references please be specific: ?the idle would hang?. What do you mean?
Thanks. Bill

 

[Nessism]

Ed, you're one of the few 550 owners who respond to questions, could your references please be specific: ?the idle would hang?. What do you mean?
Thanks. Bill

After the engine is warmed up, the idle would not drop down to the normal 1100 rpm level, or only would do so slowly. Basically, the idle would "hang" at 2000 rpm or so and not consistently move lower. This is typically a sign that the engine is drawing false air but my old 550T did this with the mixture screws in further than 3.5 turns.