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Right side carb not getting fuel?

  • Thread starter Thread starter Mr. Sinister
  • Start date Start date
M

Mr. Sinister

Guest
Hey folks,
My 81 GS450 carbs were professionally rebuilt recently. Long story short, this is how I came to own this bike. Previous owner didn't want to pay to get the carbs out of the shop, so I took the bike off his hands, and got the carbs out.
Anyway, we reinstalled the carbs, and the bike fired right up after priming. It seems to run well enough, but we decided to put a new set of NGK plus in it anyway while it was back at the shop to sync the carbs.
This is where we discovered the intake boots were shot (popping at idle, would increase rpm when we shot some carb cleaner around the boots). Turns out the o-rings that seal the boots were totally flat, and no longer sealing properly.
Once we got the bike home, we replaced the boots, we fired it up again, and the popping was gone. We tested with carb cleaner again, and no rpm increase. So we set the idle, and I noticed the right side of the motor was fairly cool, not nearly as hot as the left side.
So, I pull the plug from the right side, and it looks like it just came out of the box. We tested, and it's getting spark. So I pulled the left side plug, and it was black as night, covered in soot. We also noted a bit of grey smoke from the left side exhaust pipe, that looks to be an overly rich condition, confirming the left side cylinder is getting way too much fuel (at least in my mind).
The strange thing is the bike seems to idle and rev pretty smoothly, if not a bit slowly, but I'm not terribly familiar with these bikes yet.
So I'm left wondering if the right side carb is getting fuel. The bike is at my buddy's shop where we're putting it together, so I can't get to it 24/7 to test things, I'm just looking for some advice on where to start the next time we work on it.
Thanks!!

Edit: Thought I should add that we are using a auxiliary fuel tank for all this testing/tuning, not the stock tank and petcock. I've read that the fuels system on these bikes is finicky at best, so would that be an issue?
 
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Just to be sure- when you say left side, you mean the cylinder under the clutch lever? Where does your petcock vacuum hose connect (if you have one)- to this "left side" ?
Open the bowl drain for the non working carb to check for fuel.
 
Yes, my left hand side as I'm sitting on the bike.
The vacuum hose connects to a port on the left side carb, on the upper half if I recall correctly.
That was our thought. The guy who rebuilt and synched the carbs didn't notice or mention anything out of the ordinary (other than the popping because of bad boots). Exhaust pulses from the tailpipes feels strong and steady.
Stupid question, but the choke is off when the lever is up, right? I figured this was the case after watching what moves when I push the lever down. We've messed with a few bikes before, but this is our first GS, so please forgive my ignorance. :o
 
Mr. Sinister said:
Anyone else care to venture a guess?
Click to expand...
In your first post you said.....
"81 GS450 carbs were professionally rebuilt recently" Lots of members on here have learned the hard way that some "professionals" have little interest in old bikes. It's possible that you will have to do your own carb work -much as I like guessing, it's better to know.
 
tom203 said:
In your first post you said.....
"81 GS450 carbs were professionally rebuilt recently" Lots of members on here have learned the hard way that some "professionals" have little interest in old bikes. It's possible that you will have to do your own carb work -much as I like guessing, it's better to know.
Click to expand...


Yeah, and the assumption is he did a competent job. He SAID he's really familiar with these carbs, and he came with a good recommendation. But, I have a feeling I'll be tearing them down myself before this is all over.
I've also been thinking perhaps it's a problem with the left side carb, since we didn't run it for more than 5 minutes on these plugs, and not under a load at all. The right side plug probably shouldn't have much if any carbon on it yet. For all I know, the bike might just need to be taken out and blown out a little.

I think what I'm going to do it get the bike totally reassembled with the correct tank and petcock, and start from there. After poking around quite a bit here, and downloading a Clymer manual from BikeCliff's website, I think I have a good plan of action. Oil change, check valves, check timing, set carbs to factory specs, regap the plugs, and see where I'm at.
 
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