#2 cylinder (From the left) getting no fuel?

[Guest]

Good morning guys! So I was referred to you by a friend, and told you this is a great place to learn about our bikes. I've spent the last hour searching the forums about my problem, and none of them had solutions, or weren't exactly the problem I am having.

1981 Suzuki GS550L
17,900 miles

So my problem is my #2 cylinder is getting no fuel at all. I bought the bike two days ago and rode it home. When heading home, I noticed the bike would not go over 40 mph. From reading on the forum, this could be a spark plug issue, or fuel issue, so I started my diagnoses..

I switched the plugs, no difference.
I checked spark, and am getting a strong blue spark.
I made sure all of the lines were hooked up. (The previous owner did add an inline valve after the petcock, to shut fuel off, as the petcock only has prime, fuel, and reserve)
I checked to see if the air filter was clogged (Didn't have one in there..)
I removed the carbs, checked everything on the #2 carb compared to the rest.
The #2 carb is a different color, because it hasn't been getting fuel in there. But, the float, and everything looks good. An important note is that I drained all of the bowls, for all four carbs. All of them had gas in the bowls, the same amount also.

I've went on a 10 minute ride, pulled the plug for cyl #2 (From the left), and the plug was clean, looked brand new. I also for a second, touched the exhaust pipes for each cylinder. The cyl #2 pipe, I could hold my hand on it, and it was barely warm. The other cylinders were hot to the touch of course. So my theory is that fuel is getting to the carb in the bowl, just not to the cylinder for some reason.


My questions are:

1) Is their anything specific to Cyl #2 carb (vacuum wise, or other) that I can check? I ask this, because their is a vacuum line going from the petcock to the carb for cyl #2.
2) The carb works by vacuum, which moves the piston up and down inside the carb to pull fuel up and into the cylinder? Is the vacuum coming from the piston in the engine moving up and down, where this could be a no compression on that cylinder issue? (I hope not!) Or is their another source for the vacuum on the carb?

I am going to say I'm mechanically inclined, but not really with carbs :\ So anything I need to learn ,please let me know, thank you!

[gustovh]

Well it sounds like you need to do what most of us do when we get a new old bike. Go through them, change all the fluids, check and clean connections, adjust the valves, pull and clean the carbs per the tutorial on this website and change the intake O rings which are probably rock hard.

My guess is that the pilot circuit on the #2 carb is plugged. The original gas valve is not functioning thus the reason for the additional shut off valve.

V

[tom203]

The vacuum line from petcock to #2 cylinder lets the fuel flow from tank to all 4 carbs. The vacuum piston in each carb has no control over this- it goes up/down depending on throttle position/load and delivers mixture to cylinders.
As mentioned your pilot circuit is likely plugged and is failing to deliver.
The added fuel shut off is unnecessary unless the petcock has failed- which is very likely.

[mrdennis87]

The vacuum line from petcock to #2 cylinder lets the fuel flow from tank to all 4 carbs. The vacuum piston in each carb has no control over this- it goes up/down depending on throttle position/load and delivers mixture to cylinders.
As mentioned your pilot circuit is likely plugged and is failing to deliver.
The added fuel shut off is unnecessary unless the petcock has failed- which is very likely.

Thank you for the fast response! I agree, I am going to change the fluids (gas seemed to be dripping from the crankcase vent hose.. was told carb related) and have the carbs off to soak and clean them. I will check the site here for the link on cleaning the carbs, and I believe you guys order the o-rings from cycleorings.com. I am not sure of the type of carbs I have.. If I should order the CV, or the VM rings..? I will definitely have to make sure that pilot circuit is cleaned out. Again, thank you so much for the help guys!

Follow up questions, if you don't mind..

1) So the vacuum line from the petcock provides the vacuum, letting fuel flow from the tank down the other line, into all 4 carbs?
2) The pilot circuit, is the long metal stem, with a very small hole in it reaching to the bottom of the bowl. On the left in the picture.. This is what brings the gas from the bowl, up and into the cylinder?
3) So the no fuel into cylinder #2, is not going to be caused by low or no compression in that cylinder?
4) You mentioned that the petcock has failed, what happens if it fails? do you mean, that the one vacuum line, should control the fuel coming out of the petcock? and the petcock failed pouring fuel out constantly instead of as needed? Forgive my asking questions, I like to learn and understand how things work.

IMG_3632.jpg

[Big T]

1. Yes
2. Yes, and maybe
3. Compression could be a factor, but most likely, plugged carb
4. When it fails, the diaphragm inside it breaks, causing fuel to flow down the vacuum line into carb 2, flooding it. It can also create constant fuel flow down the fuel line, which should be held in check by the floats

Simple side test - remove the oil filler cap and smell the oil. Smell like gas and oil?

Look for the Cv carb rebuild on the BikeCliff page

[mrdennis87]

Awesome, thank you so much! I've placed the order for the CV carburetor O-rings so I can replace all of those.
I've found the instructions for the carb rebuild also.
I will have to wait until I'm home to check the oil smell, but when the crankcase vent tube was dripping I smelled the liquid and it smelled like gas.
So I'm all set, except for one more thing.. I've got the O-rings ordered, now I need a rebuild kit for the carbs.. or should I just clean them really really good and that should be ok? The other three seem to be great, just the one messing up. I promise this is my last question I will update once I've got them all clean and installed (Hopefully it's not worse putting them back in, getting them out was a pain).

[geol]

Just a thought but there are three things necessary for the cylinder to fire. Compression, spark and fuel. You can open the drain screw on your carb and if gas flows out, perhaps the carb is the culprit BUT if you were going 40 mph, the pilot circuit would not be able to shut off all fuel flow if plugged because the needle jet/jet needle is contributing fuel at this point. That leaves compression. As with any new bike, CHECK COMPRESSION right from the get-go. If you have no compression, the cylinder won't fire. Lack of compression can be from a holed piston, usually caused by air leaks through the carb holder; it can be caused by lack of valve adjustment and then there is the situation where the piston rings can't seal or you have a bent valve or a mechanical problem of this nature.

I personally would not rebuild the carburetor until I checked compression for those reasons. May be the carburetor or may be lack of compression.

[tom203]

You don't need rebuild kits- just the o-ring kit from cycleorings: the metal jets don't wear out.
As to your pilot circuit, look at this pic and see the convoluted path gas from bowl has to travel to blend with air and make it to carb throat exit- lots of tiny passages that get gummed up easily and will resist quickee attempts to clean them!

[mrdennis87]

I understand exactly what you mean. I am going to make sure to follow the guide and clean everything twice. I did notice though, when reading through the rebuild guide, my carbs are missing (or don't have?) the plug for the pilot jet. I pulled all of the bowls off last night, and none of them had that plug. Is the purpose of that plug to keep debris from getting into the pilot jet? Everything came apart nice and easy, so I'm thinking they've been apart before..

[mike10]

I understand exactly what you mean. I am going to make sure to follow the guide and clean everything twice. I did notice though, when reading through the rebuild guide, my carbs are missing (or don't have?) the plug for the pilot jet. I pulled all of the bowls off last night, and none of them had that plug. Is the purpose of that plug to keep debris from getting into the pilot jet? Everything came apart nice and easy, so I'm thinking they've been apart before..

Yes you must have those plugs. Shop around prices very. I got a set of 4 new 10 bucks on e-bay. Can't remember why they are needed right now, just woke up.

[yank]

Just a thought but there are three things necessary for the cylinder to fire. Compression, spark and fuel. You can open the drain screw on your carb and if gas flows out, perhaps the carb is the culprit BUT if you were going 40 mph, the pilot circuit would not be able to shut off all fuel flow if plugged because the needle jet/jet needle is contributing fuel at this point. That leaves compression. As with any new bike, CHECK COMPRESSION right from the get-go. If you have no compression, the cylinder won't fire. Lack of compression can be from a holed piston, usually caused by air leaks through the carb holder; it can be caused by lack of valve adjustment and then there is the situation where the piston rings can't seal or you have a bent valve or a mechanical problem of this nature.

I personally would not rebuild the carburetor until I checked compression for those reasons. May be the carburetor or may be lack of compression.

Say what! Then what would you suggest?
Sorry read that wrong. Also have your throttle wide open and a warm motor if possible.

[geol]

Yes you must have those plugs. Shop around prices very. I got a set of 4 new 10 bucks on e-bay. Can't remember why they are needed right now, just woke up.

Mike the plugs are needed as there is a hole going between the pilot well and main jet well and the pilot jet in those type carbs draws fuel through the main jet well. And anyone who has a carb that isn't flowing gas at idle and doesn't use new pilot jets is setting himself up for trouble. Cleaning jets with a jet cleaning tool abrades the orifice where gas flows and ruins the chamfer on the inlet where gas is pulled in. Just use new pilot jets... you can often get away with the original main jets. And the jets are brass but while they may not wear, if someone has been using air filtering method that is ineffective, then the needle jet will usually wear quickly and oval and performance and gas mileage will degrade. If the air filter is REALLY bad it will scour the finish off the jet needles and they are toast at that point.

[geol]

Say what! Then what would you suggest?
Sorry read that wrong. Also have your throttle wide open and a warm motor if possible.

Rebuilding the carbs in this case is more of a chore than checking compression and a new owner should baseline the bike anyway. It could turn out that a valve has no clearance. While checking the engine warm is preferable, in this case it won't matter a lot because if the cylinder isn't firing, there is likely to be very little compression in the cylinder... plus if the cylinder isn't firing, it won't get warm anyway.

One last point, never put your pinkies on a headpipe that is hot. Use a spray bottle with water and hit a pipe that is firing, The water vaporizes instantly and if the pipe isn't firing, it will be very hot from being next to the other pipes but the water will spit and sizzle.

[gustovh]

I'm sure that you realize that it is the rubber plug in this picture that he is talking about.


V

[mike10]

Good morning guys! So I was referred to you by a friend, and told you this is a great place to learn about our bikes. I've spent the last hour searching the forums about my problem, and none of them had solutions, or weren't exactly the problem I am having.

1981 Suzuki GS550L
17,900 miles

So my problem is my #2 cylinder is getting no fuel at all. I bought the bike two days ago and rode it home. When heading home, I noticed the bike would not go over 40 mph. From reading on the forum, this could be a spark plug issue, or fuel issue, so I started my diagnoses..

I switched the plugs, no difference.
I checked spark, and am getting a strong blue spark.
I made sure all of the lines were hooked up. (The previous owner did add an inline valve after the petcock, to shut fuel off, as the petcock only has prime, fuel, and reserve)
I checked to see if the air filter was clogged (Didn't have one in there..)
I removed the carbs, checked everything on the #2 carb compared to the rest.
The #2 carb is a different color, because it hasn't been getting fuel in there. But, the float, and everything looks good. An important note is that I drained all of the bowls, for all four carbs. All of them had gas in the bowls, the same amount also.

I've went on a 10 minute ride, pulled the plug for cyl #2 (From the left), and the plug was clean, looked brand new. I also for a second, touched the exhaust pipes for each cylinder. The cyl #2 pipe, I could hold my hand on it, and it was barely warm. The other cylinders were hot to the touch of course. So my theory is that fuel is getting to the carb in the bowl, just not to the cylinder for some reason.


My questions are:

1) Is their anything specific to Cyl #2 carb (vacuum wise, or other) that I can check? I ask this, because their is a vacuum line going from the petcock to the carb for cyl #2.
2) The carb works by vacuum, which moves the piston up and down inside the carb to pull fuel up and into the cylinder? Is the vacuum coming from the piston in the engine moving up and down, where this could be a no compression on that cylinder issue? (I hope not!) Or is their another source for the vacuum on the carb?

I am going to say I'm mechanically inclined, but not really with carbs :\ So anything I need to learn ,please let me know, thank you!

You also must have an air filter in the air box or it will not run right . You will not be able to do proper carb adjustments