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Alright finally some diagnostic stuff

  • Thread starter Thread starter satchmo
  • Start date Start date
S

satchmo

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1977 gs550e

As many of you know I'm getting horrendously band mileage.

I pulled all my plugs today. All of them black, including the porcelain. Kind of like #3 but not so lumpy...

http://www.dansmc.com/Spark_Plugs/Spark_Plugs_catalog.html

So I guess I'm running really rich, besides that I have no weird rattles, or vibrations, occassionally misfires when I let off the throttle.

Good power, good response.
Oh yeah, and the head of the air screw on Carb 1 is pretty much stripped, so I can't turn the thing in any direction.


So what the heck do I do now?

Satch
 
Don't worry too much about the one air screw, you can probably work around it. See if someome here can tell you what the correct jet sizes are. If they can't try moving the needles down a notch at a time and go down a size or two on the mains. Someone in the past probably thought more fuel was a good idea. Could also be retarded timing or a combination of both carbs and timing.
 
Re: Alright finally some diagnostic stuff

Alex, I wouldnt (as Billy says) worry about the airscrew. Idle mixture on that cylinder can still be compensated by fuel flow with the pilot screw.

Now, as for your symptoms, it could be ignition, timing, carbs, jetting, induction, floats, valves or electrical or any combination of small things that together become major. There really is no way to know exactly what the problem is right off. I think the best way to go about it is to progress through everything making sure each step is working properly befor moving on to the next. The order that you would usually check things is electrical (voltages and connections), induction (aircleaner and boots),
ignition (points, plugs, plug wires, plug boots and timing), carbs (settings, adjustments , jets and synchronizing)

Carbs are usually the last thing you work with when you are sure everything else is as it should be because if anything in the various stages of setup are not correct, you will not be able to adjust carbs to get the bike to run correctly. I know everyone wants to take the "shortcut" and jump directly to carbs, but I feel that is a mistake in the majority of the time. Its your bike, so we can start wherever you wish, but my suggestion is that we start with making sure the electrical system has the correct voltage in a few key places.

Your thoughts????


Earl


satchmo said:
1977 gs550e

As many of you know I'm getting horrendously band mileage.

I pulled all my plugs today. All of them black, including the porcelain. Kind of like #3 but not so lumpy...

http://www.dansmc.com/Spark_Plugs/Spark_Plugs_catalog.html

So I guess I'm running really rich, besides that I have no weird rattles, or vibrations, occassionally misfires when I let off the throttle.

Good power, good response.
Oh yeah, and the head of the air screw on Carb 1 is pretty much stripped, so I can't turn the thing in any direction.


So what the heck do I do now?

Satch
Click to expand...
 
Thanks for posting that link, I'm running a 14 which appears to be pretty good :D Before troubleshooting my petcock I was running a 20 but even whiter, what a difference! :)
 
Earl, Thanks for the tip. Electrical here I come. Alright, what do I gotta do :)

I mean, to be quite honest I don't quite understand how the electrical could give that result in the engine :oops:

Satch
 
A drop in voltage at the coils, from faulty connections and such, will cause a weak spark resulting in black plug syndrome. Thats just one place electrical to start. :twisted:
 
Your plugs are running black. That represents incomplete combustion of the mixture. It could be too much fuel and not enough air. That could mean too large a carb jet, or it could mean a clogged air intake filter, or it could mean your jets are perfect, the air filter is perfect and you just dont have enough electrical power getting through to the ignition system to run it properly.
Lack of electrical supply would result in a weaker spark. The spark being normal strength, but the timing being severly retarded could also cause incomplete combustion and black plugs. Any of these things can cause fouled plugs and poor gas milage.

Keeping it quick and easy. Just take a voltmeter or multimeter and check at the battery terminals to see what the battery voltage is. Then leave the positive meter lead on the + battery terminal and put the neg lead to ground on the engine. The voltage reading should be the same.

Next, remove the gas tank and you will see the two coils. The striped wires coming from the ignition will be connected to the + terminal on each coil. Switch on the ignition and put the + lead of the meter on the striped wire end. Put the neg lead of the meter on the engine case or any grounding point on the frame (bare metal). Do this for both coils.
We know the voltage we have in the battery and now we want to know what is actually getting through the wiring harness, ignition switch, etc, and arriving at the coils to power the spark plugs. In an ideal world, the voltages would all be the same, but they will not be. On my 750, I have about a 1/4 volt drop due to system losses, resistance, etc.

Let me know what voltages you record, and then we can decide if something needs attention or we can go onto the next step.

Earl


satchmo said:
Earl, Thanks for the tip. Electrical here I come. Alright, what do I gotta do :)

I mean, to be quite honest I don't quite understand how the electrical could give that result in the engine :oops:

Satch
Click to expand...
 
Earl,

It has become obvious to me that you must, you absolutely must, move to Massachusetts immediately! Drop everything you are doing, leave behind all your Florida life and family and friends and job and memories and warm winters, and move right this minute to Massachusetts, so that I can ride to your house and watch you work on my bike while I drink beer!

Geez, oh geez, I wish I had someone with your GS know-how, right around the corner from me! The mechanic I use is pretty good, but you got this whole GS thing licked!

Most, if not all, of us on the GSR have benefited from your GS knowledge and good humor. Thanks for being here.
 
Aw Brion, all I do is break it down into small pieces that I can understand. :-)

Earl


bgk said:
Earl,
Geez, oh geez, I wish I had someone with your GS know-how, right around the corner from me! The mechanic I use is pretty good, but you got this whole GS thing licked!
Click to expand...
 
Thanks Earl. Give me a couple of days then I will post again. I really appreciate the help.

Satch
 
Not a problem alex, I got the time if you got the........ :-) :-)
We'll get her sorted out. eh eh

Earl

satchmo said:
Thanks Earl. Give me a couple of days then I will post again. I really appreciate the help.

Satch
Click to expand...
 
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