#1 pipe cold

[egetron]

Hey guys.

I have a 1980 GS550. Right now the bike runs pretty well, the only problem is that the first cylinder is not getting hot while idling, and when I run it for a while, it doesn't feel as hot as the others.

What I've done so far:

I've rebuilt the bottom end to fix a transmission issue successfully, which was great. Thanks for all the help on that. That thread is here:
http://www.thegsresources.com/_forum/showthread.php?t=206259

I had some starting issues which I resolved here:
http://www.thegsresources.com/_forum/showthread.php?t=216084

To summarize, since acquiring the bike, I've:
-Thoroughly stripped/dipped/cleaned carbs twice according to BikeCliff tutorials and replaced all o-rings.
-Replaced spark plugs
-Brand new, freshly charged battery.
-New Intake O-rings
-Checked for air-leaks
-Checked float heights
-Replaced exhaust gaskets
-Checked valve clearances (I had some trouble with this because everything was covered in oil... my clearances seemed to be ok but I'm wondering if I forced in the gauge with too much pressure)




What else should I be checking?

 

[almarconi]

Check for spark and compression on that cylinder. Check the plug wire from the coil. Re clean the #1 carburetor paying special attention to the pilot circuit.

 

[tkent02]

And the choke feed passage in the float bowl.

 

[Steve]

Did you sync the carbs?

With the very small clearances on the valves, there is no way to "force" that very thin feeler in there.
It will fold LONG before you can force it where it won't fit.

Even though you have "cleaned the carbs twice", don't rule out the possibility that something has gotten into the pilot passage of #1 carb.

.

 

[Crankthat]

Did you sync the carbs?

With the very small clearances on the valves, there is no way to "force" that very thin feeler in there.
It will fold LONG before you can force it where it won't fit.

Even though you have "cleaned the carbs twice", don't rule out the possibility that something has gotten into the pilot passage of #1 carb.

.

Been there!

 

[tkent02]

I bet the bike in question has sat a long time on the side stand?

 

[Wingsconsin]

What is your idea here ?

What is your idea here ?

I bet the bike in question has sat a long time on the side stand?

Fuel trickling over to the #1 and turning to varnish ...?

 

[tkent02]

It's always #1 or whichever one the vacuum line comes from.

 

[egetron]

Bike has not been on the side stand... It's always on center stand. My petcock vacuum line is attached to #2

I synched the carbs with a vacuum gauge.

I really cleaned the **** out of the carbs. Full dip in Berryman's for 24 hours (I did this twice on #1 carb just to make sure). sprayed and poked out every imaginable crevice with carb cleaner and compressed air.

If I've changed plugs, swapped the 1 and 4 plug wires and the problem persists... can I rule out electrical as the problem?

 

[tkent02]

Bike has not been on the side stand... It's always on center stand. My petcock vacuum line is attached to #2

I synched the carbs with a vacuum gauge.

I really cleaned the **** out of the carbs. Full dip in Berryman's for 24 hours (I did this twice on #1 carb just to make sure). sprayed and poked out every imaginable crevice with carb cleaner and compressed air.

If I've changed plugs, swapped the 1 and 4 plug wires and the problem persists... can I rule out electrical as the problem?

How did you synch the carburetors? One single vacuum gauge or a set of four?

 

[egetron]

Set of 4, Morgan Carbtune.

 

[tkent02]

You cleared the choke fuel feed passage in the float bowl?

 

[Maddevill]

Cleaner and air may not be enough to clear the tiny passages the idle circuit works on. You may need to get one of those Motion Pro carb wire kits and actually push a wire through the pilot jet and it's passage.

 

[egetron]

Choke passage in the float bowl is clean clean clean... It got dipped with the rest of the carb and when I sprayed it with carb cleaner, the spray came out the other end in a clean, uninterrupted jet.

I can try re-cleaning the 1st carb over and over, but I'm not feeling confident that's going to solve this issue.

 

[tkent02]

Make sure you get the tiny transition ports behind the first one the pilot jet goes into. There are one, two or maybe three transition ports right behind the first one. Also the air passage from the intake side of the carb to the pilot circuit?

There's really not much else.

 

[Steve]

When you have your "cold pipe" symptoms, does it also sound like it's running on just three cylinders? :-k

Just for fun and games, while it is idling, turn the mixture screw on #1 out another turn or two.

My son's 650L has one carb that need the screw out about 4 turns, while the others are about 2 1/4.

.

 

[egetron]

I'm not sure how to tell if if it's on three cylinders.

While it's running, if I unplug the spark plug of the cylinder in question, the engine does begin to gurgle and die out, albeit somewhat slowly. If I do the same with any of the other cylinders, it dies out immediately.

 

[tkent02]

That should tell you something. Normally a four cylinder GS will keep running just fine on three cylinders, although it would be a little rough. It will idle, and it will rev up, you can ride it around just fine, just has about 25% less power… More like 35%.

 

[Wallowgreen]

First thing to say is Tom and Steve know exactly what they're talking about with these kind of problems. But, here's my experience with his kind of problem take it as it's intended, just an extra data point.

I spent many, many months working a similar problem on both my 850 and 550 Kat. I stripped, dipped, sprayed and shot compressed air through everything about a bazillion times on both racks of carbs. I even took the set from the 550 to the lab at work to xray the bodies so I could visually inspect the micro bore passages inside them. All looked good and open as far as both the technician and I could tell. Then I wasted months looking elsewhere for the problem.

Then a set from a 550L that had the same part numbers for each individual carb came up for sale on fleabay for $35. I bought them, did the usual clean with my ultra sonic cleaner and put them on. Hey presto! Never had any problems since.

Same thing fixed the 850.

So while I concur with the clean your carbs routine, I've also found that some bodies just can't be cleaned good enough. I guess you can argue anything can be cleaned if done properly and maybe so. But at the end of the day I got fed up with taking carbs off, cleaning them and refitting them that I say just get a spare set, clean them and try them. See if that fixes your problem.

 

[almarconi]

I find it so tiresome to offer advice to some people on this forum. No matter what you suggest they already have a counter response yet their problem still exists. This thread is an example of this. No matter what is suggested the problem will not be fixed because the OP already has all the answers. Why bother to offer advice to people who already have all the answers and know how to solve the problem?