Just picked up a GS on Friday, and she's already sick!

Symptoms:

Down on power
Rev it up when it's just sitting there and it revs to 11K without a problem, under a load, it struggles for 7k.
Will just sudenly die out and have a hard time starting again
Has a hard time getting past 60MPH going up hills on the freeway
Leave it idling for more than 5 minutes and it will just die
very very rattly, knocky and clattery noises from the motor, I've heard lawnmowers that sounded WAY healthier.
There is a hole in the round cover on the right side of the bike. I can see what looks like a large 17mm bolt that is not spinning in a circle when the motor is running. Looks more like an eliptical orbit.


Checks I've done:

Removed ALL fuel petcocks, so that the motor gets a direct feed of fuel, we thought it was a petcock problem, but it is not fuel starvation
Checked the spark plugs
Checked the coils to make sure it's getting spark
Checked the carbs for proper opperation
Checked the compression on the motor both hot and cold and it comes up to right around 118 psi on Both cylinders.

I checked the compression by removing one spark plug, unplugging the coil on the other side, putting the tester on, and cranking the engine over several revolutions with the throttle both open and closed. Between 118psi and 122psi on both cylinders, hot or cold.

Do I have a totally trashed motor?

  Ummm the spinny thing  is your ignition rotor and if it's moving in an ellipse you probably only have spark on one side or inconsistant spark on both sides

Bad gas will rev fine but crap out under load, but I don't think that's the problem

He's right ... that spinny thing is your ignition rotor.
However you take off that cover and look at it. When the bike is not running, and you turn it by hand, you see that its nose gets to the same distance on both the 2 pick up points ... that means its OK. your problem is else where. More than likely.
I think carbs ...
Cool.
Srinath.

Ok, one more symptom I forgot.

When it is idling, when I pull just the right spark plug wire off, it will stay running, but a just a tad rougher.

When pull just the left spark plug wire off, it immediately dies.

sounds like only one cylinder is running?

Quote from: Gabriel Tyler on May 07, 2007, 11:06:54 AM
Ok, one more symptom I forgot.

When it is idling, when I pull just the right spark plug wire off, it will stay running, but a just a tad rougher.

When pull just the left spark plug wire off, it immediately dies.

That means the right cylinder isn't firing correctly.  

The list of symptoms mostly point to you're running on one cylinder.  You just have to figure out why.  I'd start with a thorough carb cleaning/o-ring replacement, valve adjustment, and carb balance.  

The low compression and clattery sounding motor low compression aren't things to be worried about, just quite yet, then?

Note that I said "mostly."  The cause of it running on one cylinder could very well be the compression.  However, if I'm not mistaken, isn't the service limit something like 110 psi?  I don't have a manual handy.

Also, you're going to get bad readings until you get both cylinders running.  It won't get up to temperature correctly.

You might invest in a mechanic's stethoscope.  They're relatively cheap, and you can use them to determine the location of the noises (e.g. head, pistons, bottom end, left vs. right).  A stethoscope with a metal probe works better than a piece of hose or screwdriver (less damping of the noise), but those will both do in a pinch. 

Your motor might be hosed, but then again, it might be valves and/or cam shaft end play.  One step at a time though.

Usually 1 cyl probably is vaccum leak, vacuum line problem especially if it also has a "only running in prime problem" or auxillary ground problem.
Cool.
Srinath.

Or a stuck needle valve.  Or a clogged jet.  Or unbalanced carbs.  Or a bad coil.  Or a bad plug.  Or a bad plug wire.  Or misadjusted valves.  Or a bent valve.  Or leaking valve guides.... 

Or in other words, it could be many, many things.  Further diagnostic work is required to narrow down the possibilities.

1 clean/adjust the carbs and change the oil to 20W-50
2 while you have the carbs off....do a compression check
          114 is low limit
          standard is 142-199
          max diff between sides.....28
  actually better to do on a hot engine but....whatever, it will get you in the ball park

3 if still low.....add a little bit of oil to the spark plug hole and see if compression goes up
4 check your valves and retorque the head while you are there
5 sync carbs

Thanks for your input guys!

I took the rotor cover off and the bolt that holds the rotor onto the crank was broken off (the head of which had dissapeared).

The rotor had been flopping around and done quite a number on the points! I'll replace the rotor and points and see what happens!

Ummm that could be a problem   How the hell do people do this to a GS  Mine never skips a beat and we all know about my riding habits

Quote from: Gabriel Tyler on May 07, 2007, 11:06:54 AM
Ok, one more symptom I forgot.

When it is idling, when I pull just the right spark plug wire off, it will stay running, but a just a tad rougher.

When pull just the left spark plug wire off, it immediately dies.

Uh... for those that recommended servicing the carbs and fuel....last time I checked the spark plugs are electrically operated...I could be wrong though 

Gabriel,
I crashed at the track in 95 or so and the 6mm bolt broke some time later
and it did a number on the pickups
did you get the broken bolt out?
wrap some wire around the pickups if they are not completely trashed
and try starting the bike....i used safety wire and rode it that way for a yr or so til i found the part

Quote from: dgyver on May 07, 2007, 06:08:06 PM

Quote from: Gabriel Tyler on May 07, 2007, 11:06:54 AM
Ok, one more symptom I forgot.

When it is idling, when I pull just the right spark plug wire off, it will stay running, but a just a tad rougher.

When pull just the left spark plug wire off, it immediately dies.

Uh... for those that recommended servicing the carbs and fuel....last time I checked the spark plugs are electrically operated...I could be wrong though 

it could have been poorly synched carbs....but the igniter coils will definately cause the problem

Sounds like you found your problem with the ignition setup. Look on ebay/wrecking yards etc for the ignition pieces that you need.

Quote from: dgyver on May 07, 2007, 06:08:06 PM

Quote from: Gabriel Tyler on May 07, 2007, 11:06:54 AM
Ok, one more symptom I forgot.

When it is idling, when I pull just the right spark plug wire off, it will stay running, but a just a tad rougher.

When pull just the left spark plug wire off, it immediately dies.

Uh... for those that recommended servicing the carbs and fuel....last time I checked the spark plugs are electrically operated...I could be wrong though 

His problems weren't necessarily spark plug related.  It's was simply one cylinder not running, which can be easily determined by taking off the plug wires.  Mine ran with one cylinder, and it was all carburetor (unbalanced carburetors, clogged jets, non-operational choke, and gods know what else).  It just so happens that carbs are the easiest and cheapest to check and fix, as well as being the most common problem with the GS.

This time, apparently it wasn't. 

Quote from: spcterry on May 07, 2007, 06:02:14 PM
Ummm that could be a problem   How the hell do people do this to a GS  Mine never skips a beat and we all know about my riding habits

I figure what happened is that someone tried to hand-crank the engine with the small bolt instead of the large one, with obvious results.    Sounds like something you would do, special. 

My point to that was no one suggested checking anything electrically related. Yes it could be carb related but the odds are greater that it is electrically related with the info provided. Heck checking electrical most components is normally free, as long as you have a voltmeter.

Ummmm.....yeah I'm not quite that retarded   With the exception of getting air screws right I'm pretty good with a wrench.............God don't let the military know   They wont let me shoot stuff anymore