i have no clue why cylinder 3 & 4 are cold please help!

[steve_crabb]

I have a 1981 GS550 and cylinder 3 and 4 are running cold! i pulled the plugs and they are getting spark but i don't know where to go from here. i just changed the oil replaced the petcock and cleaned the tank, i also took off the screws on the botom of the bowls and sprayed carb cleaner up there and put on a new air filter. the bike fires up and idles but has no power due to the fact it is only running on one cylynder. i'm hoping it is nothing to complicated and any advice will help since i don't know much about working on Bikes and this is my first bike.

[blackwolf]

Maybe you not getting any fuel to the other cylinders.So it might be that your floats in carbs are not level or maybe you have blocked jets.

[Nessism]

Sounds like a classic case of gummed up carbs.

[Steve]

I am just a bit cornfused here...you say that #3 and #4 are cold, but it's only running on ONE cylinder? Would that be #1 or #2? If it's only running on one of them, why isn't the other one cold, too?

As I see it, the only thing that 3 and 4 have in common is the right carburetor (this is the model with two 2-barrel carbs, right?). I would open the drains on both carbs and compare the amount of gas that comes out. It is possible that the right carb (for #3 and #4) will be dry, or at least not have as much as the left carb. Look for a plugged screen on the inlet to the carb or mis-adjusted float level. It would also be wise to check the floats. If there is a hole in the float, it will not float at the right level, so the fuel level will be off, too.

[Nessism]

I am just a bit cornfused here...you say that #3 and #4 are cold, but it's only running on ONE cylinder? Would that be #1 or #2? If it's only running on one of them, why isn't the other one cold, too?

As I see it, the only thing that 3 and 4 have in common is the right carburetor (this is the model with two 2-barrel carbs, right?). I would open the drains on both carbs and compare the amount of gas that comes out. It is possible that the right carb (for #3 and #4) will be dry, or at least not have as much as the left carb. Look for a plugged screen on the inlet to the carb or mis-adjusted float level. It would also be wise to check the floats. If there is a hole in the float, it will not float at the right level, so the fuel level will be off, too.

I'm assuming that he doesn't know exactly how many cylinders are misbehaving but it seems that at least two are since the pipes are cold.

Regarding the reason, it's not likely to be float height related; the floats don't just change their height and the main pickup for the engine feed is at the bottom of the float bowl so as long as any gas is getting in there, there shouldn't be an idle issue. Most likely the issue is that the idle jets and low speed jets are plugged up. The orifice hole through these jets is VERY small so they clog easily. Of course, it could be that the float is stuck closed due to gunk as well. In any case, the carbs should come off to check everything over. Contrary to what some stay, you can do a good job of cleaning by taking the carbs off the bike, removing the float bowl, remove the float and ALL the jets, and then spraying everything down with some good carb cleaner. It may take several cans but I find this easier than taking the carbs off the gang like some do.

Good luck.

Ed

[steve_crabb]

my confusion continues about the cold pipes!

I sprayed some starting fluid in the two right carbs and it seemed to bog down and back fire! then i completely switched the negative and possitive wires that go to the two coils and the problem switched to the other two pipes, so 3 and 4 were running hot and 1 and 2 were then cold. does this mean i have bad coils or do i need to look into something else? thank you for your help (i'm guessing i'll still need to take off the carbs and clean them out but this has me baffled!) any advice will be a big help! thanks!
steve

[Nessism]

My first thought is that you have a harness problem but then I'm not really sure. Maybe a little jumper harness is in order so you can wire it the way it runs best as a test?