Is This Right? Carb Question

[Guest]

I took my carbs off of my GS 550 to get to the intake boots/o-rings. I noticed that the cylinder (the part that holds the large needle) is set lower on the 3rd carb compaired to the other three carbs. #1, 2 and 4 carbs has about 1/8" of the needle showing above the brass piece (the part that has the jet screwed into the end of it) where carb #3 has only about 1/64" of the needle showing.

Is this right? I took some pictures to show what I'm talking about, but the camera died just after taking the pics. I'll post pics here after it recharges.

[Nessism]

Something is wrong. Stick your finger into the throat of the carb and manually lift the piston. It should lift easily without restriction. With the piston in the upper most position, let go of it and it should slide down with a damped action - and make a solid clunk when it reaches the stop on the bottom. Report back on what you find.

[Colorado CJ]

The pistons all act the same (slide down slowly) and seat with a "klunk". Here is the picture. The #2 carb is on the left and you can see that about 1/8" of the needle is exposed when it is fully seated (same as #1 and #4). The #3 carb is on the right and the needle is only exposed about 1/64" not nearly as exposed as all other carbs.



I took apart both #3 and #4 carbs and can't see why #3 is this way, all parts look the same and both have the same jet size. Both jets are clean as well.

Any help would be appreciated

[Nessism]

You might want to pull that #3 carb apart and compare the parts to one of the others since something is different. Maybe the slide has been replaced at some point with a similar, but not identical, version?

[catbed]

so they PO set the 1,2 and 4 carbs richer than 3 in the needle circuit. to adjust this, you need long reach pliers to take the locking ring off and take the needle out. it sounds like you either have after market needles or the spring in the stock needles broke.

[tkent02]

Looks to me like the slide is closing farther than the others, why would this be?

[chuckycheese]

Needle jets?

How come the needle jets are sticking up into the lumen of the carb body??

[Colorado CJ]

Yeah, the piston on #3 slides further down than all the others for some reason. I don't see why it is doing it myself. I thought maybe since the #3 carb is the carb all others go by, it is set different. Really don't know.

[Nessism]

Maybe one of the main jets is loose and the jet needle is raised up too high? Not sure but what’s going on, but I am sure something is wrong.
In my opinion, it’s time to pull down the carbs and go through them. Order up an O-ring kit from Robert Barr if they haven’t been done recently.

[Colorado CJ]

Well I found out why the #3 carb has the slide farther down in the barrel than the others, it is too long. The #3 slide is about 2.5mm longer than the other slides.

Is this right, or has the p.o. put the wrong slide in #3? I placed the #3 slides in the other carbs and it is at the same place as in the #3 carb.

I have a small lathe in the garage and I'm wondering if I should turn the end of the slide down to match the other slides overall lengths. The slide also has a larger bevel around the radius compared to the other slides.

Anyone else have a longer slide in the #3 carb?

[chef1366]

I don't think you will ever run right with the wrong slide. Find a rack on ebay or see if someone here has an extra slide/carb/rack.

[robertbarr]

I'd bet some PO found a bad diaphragm and swapped in this from a seemingly identical carb.

Maybe post in the Parts Wanted for a slide/diaphragm for that year bike. There's bound to be an eligible organ donor from all the carbs I hear about with ruined threads.

Meanwhile, if you use socket head cap screws on the diaphragm cover (M5 x 12, I think), you can swap in the replacement with the carbs in place on the bike. I'd reassemble the carbs (using the mutant slide), put it back together and give it a quick sync. Ride it until you find the slide you're looking for.

[Colorado CJ]

Posted in the wanted section yesturday morning and now have a slide/diaphragm coming in the mail today from XenoMorph.

Thanks for the heads-up about the wanted section, can't believe how fast it was!

Hopefully this will settle the high idle speed problem. I also did a washer swap on the main needles and that helped some. I can now get it down to around 1500 idle speed. It also runs much smoother and has more power compaired to before the washer swap (think it was running too lean before, here at ~5,000 ft).

[Colorado CJ]

Still Need Help!

Got the slide in from XenoMorph today (thanks again for the fast shipping!) and compared it to my other slides. It is the same length as the slide in #3 carb. Does anyone have a slide handy that they could measure for me?

The longer slides (the new one and the one in #3 carb) are 55.78 mm in length (measured with calipers) and the shorter slides (in #1,#2 and #4) are 54.55 mm in length. This is measuring from the base of the slide to the top of the plastic piece above the diaphragm.

I'd REALLY like to know what is the correct length for the slide as now I don't know if my #3 slide is correct and all others are wrong or vise versa.

[Nessism]

I have a brand new slide in a box, P/N 13500-47070, and it measures 55.68mm. This part number is called out for the '80 GS550L. Not sure what's going on with your carbs.