81 GS650 engine help

[rahlberg]

Those of you that helped me get my 81 GS650 up and running, I really appreciate it. Nothing like the roaring sound of an engine coming to life.

Well, after a bit of playing with it, I'm finding out a bit more about what it does and doesn't do.

She starts up and idles fine. As I start to give it a little gas, the RPM's start to rise, but then as I give it more gas, the RPM's will drop and the engine will die. I've also noticed that with the choke on, the engine will die (it'll start with the choke off).

I'm working on cleaning up the carb, but have yet to pull it apart to do a full clean. This is a second hand bike, so I'm not sure if the needle settings are all jacked up or what.

Can anyone sugest what I should start looking at? Also, where can I find the factory specs the carb was set to?

Any help is appreciated.

Thanks!

Russ

[waterman]

Russ,
This link, which is at the top of the technical section, should have the factory jetting information that you seek.

http://www.thegsresources.com/_forum/showthread.php?t=73723

We all feel your pain at trying to sort out a new used bike, but the easiest way to get the bugs worked out is to start with a thorough carb cleaning with oring replacement, followed by a check of the valve clearances. A new battery and some fresh gas will usually get these running.

Your reported conditions are difficult to decipher, trying to diagnose with dirty carbs isn't easy. It sounds like it is rich, no choke to start, dies with any gas. This could be a petcock that is leaking, incorrect fuel level, or many other situations. I have a 550 that will die if given too much throttle when still cold.

Honestly, clean carbs and give it another go. Please report back as we like to hear success stories.

[rahlberg]

Thanks waterman. It makes sense to knock out the obvious first.

As they say....somewhere, but I can't remember where, "cover me, I'm going in...!"

I'll be back with a full status report.

Russ

[chef1366]

Carb cleaning is in order.

[KRISTI'SGS550]

Thanks waterman. It makes sense to knock out the obvious first.

As they say....somewhere, but I can't remember where, "cover me, I'm going in...!"

I'll be back with a full status report.

Russ

If you are cleaning your carbs I recommend pulling them completely apart and the bodies and components in the Barryman's carb bath. I just did that with mine and they came out so clean!

Cory

[rahlberg]

Starting Prob

Well, I finally got through the carb cleaning. Looking at the PDF and the images, it sure looked intimidating, but once into it, it was pretty easy. Pulling parts off, I found lots of bits of dirt and dust down in the nooks and crannies of lots of the parts. It's a wonder it even idled previously!

Now I've got the carb cleaned, new o-rings, and back together. I went to fire her up, and the starter just cranked over and over, but nothing. I thought it may be a weak battery, so I jumped it from my truck, and there was noticibly more power trying to turn it, but still nothing. Before I cleaned the carb, I was at least able to get it started and idle, but now it doesn't even fire.

Some things that I've checked out:
-Fuel is getting into the float bowl (I opened the drain screw and confirmed);
-Fuel is getting to the plugs (I pulled the plugs and confirmed this);
-The #1 plug was carbon fouled, but the other 3 were fine (carb set too rich previously???)
-I pulled each plug and checked for a spark in a dark garage and got nothing.

I don't know if it's the coils, or the igniter feeding the coils that may be the problem. With the key and switch on (getting ready to start it):
-I put a voltmeter across the left coil wires (the W and O/W ones) and the volt reading was about 8.5V
-I put a voltmeter across the right coil wires (Y/B and O/W) and the volt reading was a little over 0V (I was surprised that it didn't match the other coil)
-I pulled the wires off the left coil and took a volt reading directly into the wires and it was reading about 11.5V
-Did the same on the right (w/o connected to the coil), and it was reading about 3.5V
-I checked the voltage of the battery and it was reading about 12.5V (probably down a little since I tried a number of turn overs).

A few things I've concluded, but I don't know if they're correct:
1.) The coils may be fine, there's just not enough power supplying them??
2.) Could the igniter box be bad since it's what the coils connect to?

So what do you think? Any ideas? Any other suggestions I should look at?

Thanks

Russ

[tkent02]

Well, I finally got through the carb cleaning. Looking at the PDF and the images, it sure looked intimidating, but once into it, it was pretty easy. Pulling parts off, I found lots of bits of dirt and dust down in the nooks and crannies of lots of the parts. It's a wonder it even idled previously!

Now I've got the carb cleaned, new o-rings, and back together. I went to fire her up, and the starter just cranked over and over, but nothing. I thought it may be a weak battery, so I jumped it from my truck, and there was noticibly more power trying to turn it, but still nothing. Before I cleaned the carb, I was at least able to get it started and idle, but now it doesn't even fire.

Some things that I've checked out:
-Fuel is getting into the float bowl (I opened the drain screw and confirmed);
-Fuel is getting to the plugs (I pulled the plugs and confirmed this);
-The #1 plug was carbon fouled, but the other 3 were fine (carb set too rich previously???)
-I pulled each plug and checked for a spark in a dark garage and got nothing.

I don't know if it's the coils, or the igniter feeding the coils that may be the problem. With the key and switch on (getting ready to start it):
-I put a voltmeter across the left coil wires (the W and O/W ones) and the volt reading was about 8.5V
-I put a voltmeter across the right coil wires (Y/B and O/W) and the volt reading was a little over 0V (I was surprised that it didn't match the other coil)
-I pulled the wires off the left coil and took a volt reading directly into the wires and it was reading about 11.5V
-Did the same on the right (w/o connected to the coil), and it was reading about 3.5V
-I checked the voltage of the battery and it was reading about 12.5V (probably down a little since I tried a number of turn overs).

A few things I've concluded, but I don't know if they're correct:
1.) The coils may be fine, there's just not enough power supplying them??
2.) Could the igniter box be bad since it's what the coils connect to?

So what do you think? Any ideas? Any other suggestions I should look at?

Thanks

Russ

Are the spark plugs sparking?

[rahlberg]

No, the plugs aren't sparking. That's why I started checking voltages. I wasn't sure if enough power was getting to the plugs to make them spark.

[chef1366]

Check the ignition fuse after trying to jump off the car.

[tkent02]

Try running a wire from the + on the coil to the + on the battery?
If it helps, read about the relay mod discussed here this week.

That would eliminate low voltage causing a problem.

[rahlberg]

Check the ignition fuse after trying to jump off the car.

The ignition fuse looks good (as do the other 3).

[rahlberg]

I'll give this a shot tomorrow morning. If this works, is it ok to leave this wire on? Or should I make some other permanent change?

Is this the thread for the relay mod you're talking about?

http://www.thegsresources.com/_forum/showthread.php?t=120748

Try running a wire from the + on the coil to the + on the battery?
If it helps, read about the relay mod discussed here this week.

That would eliminate low voltage causing a problem.

[tkent02]

I'll give this a shot tomorrow morning. If this works, is it ok to leave this wire on? Or should I make some other permanent change?

Is this the thread for the relay mod you're talking about?
http://www.thegsresources.com/_forum...d.php?t=120748

Yes, that's the thread.
No don't leave the wire on, it's just to check for spark.
It's exactly the same as hotwiring a car to steal it.
Leaving it connected would be the same as leaving your key switched on, battery dies, points/ignitor burns up, it's all bad.
Only leave the wire hooked up for a few seconds to check the spark.
If it has spark with the wire in place, do the relay mod, or go through and clean up every little switch and connector between the battery and the coils to get the voltage up where it should be.
(the relay is easier)
If it does not spark with the wire in place you have more troubleshooting to do.
Could be your battery is lower now and not quite sending enough voltage to the ignition to run it properly while cranking the engine...
Try charging the battery first.

[Nessism]

Hope the truck you jumped off was not running or you might have fried some components on your GS.

No spark can mean many things. Take a new plug and recheck the spark. If still no spark, check the fuses and electrical connections. On my old 450 the connector for the ingitor was loose and sometimes would loose continuity.

Good luck.

[rahlberg]

Well, I "hotwired" the engine and barely breathed on the starter button and she roared to life! \\/ Looks like there was some major losses between the batt and the coils.

The next step will be to implement the relay modification. It sounds like that'll make a world of difference. I'll let everyone know how it works out.

Thanks for the advice this far!

Russ

Yes, that's the thread.
No don't leave the wire on, it's just to check for spark.
It's exactly the same as hotwiring a car to steal it.
Leaving it connected would be the same as leaving your key switched on, battery dies, points/ignitor burns up, it's all bad.
Only leave the wire hooked up for a few seconds to check the spark.
If it has spark with the wire in place, do the relay mod, or go through and clean up every little switch and connector between the battery and the coils to get the voltage up where it should be.
(the relay is easier)
If it does not spark with the wire in place you have more troubleshooting to do.
Could be your battery is lower now and not quite sending enough voltage to the ignition to run it properly while cranking the engine...
Try charging the battery first.