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Just Rebuilt Carbs Much Better But Not Right

  • Thread starter Thread starter GTGS
  • Start date Start date
G

GTGS

Guest
:DI have an 81' Gs550L purchased a few months back. The bike was running well when I got it but soon after started running bad at idle and then I noticed alot of gas in the air box and the plugs were black. I changed the oil and removed the carbs for cleaning and rebuild. I followed the procedures on this site and she fired up and idles well. No more leaks!! I installed a new K&N filter and the airbox is sealed properly. When I rev it up to 3-4000 and hold it, sometimes it bogs. If I shut it off and prime the carbs it works fine. I also noticed that the vacuum line from the carb to the petcock is pretty old and dried up (no cracks) I will replace that right away. Plug color is perfect on 1,3,4 # 2 is rich. I should also mention that it has new manifolds. No leaks. I guess my question is, does this sound like fuel starvation? Float height or weak worn out petcock? Also please keep in mind that this is all on the stand since the rebuild.
 
Welcome to the GSR!
You have a bad petcock which is the likely reason for the #2 plug running rich. I assume that you've set them all correctly as you mention color on the other 3 is spot on.

Buy a new petcock, replace the vacuum line and fuel line and ride the bike.

A slight bog at the RPMS you mention sounds a little lean on the pilot circuit. :-k Which carbs do you have? Still have the stock exhaust?

Basscliff...
 
BS32SS carbs. I also drilled the covers from the idle screws. They are set at 1-1/2 turns which is where they were from the factory. When I first started it, it fired right away and ran pretty well. I wanted to richen the idle a little so the next day I opened them another turn and it wouldn't start. I turned them back to the original setting and the next day it fired right up again.
 
1.5 turns is way to lean for a stock 550, particularly one with a K&N air filter. I'd try 3 turns and then tune from there to archive the highest idle speed. If you are getting a rich mixture at idle at 2.5 turns something else is wrong.
 
Well I have some new info. I just went out to start it and this seems to be what happens every time. I prime the carbs, pull the choke and it starts right up and idles nicely. Once it starts to warm up I push in the choke and it idles ok. When I go to rev it up a little I get BRRRRRR and it seems like its starving. I shut it off and re-prime because the fuel doesn't seem to flow through the clear filter very quickly. I re start and she runs great, fuel flow seems good after doing this and it revs hard and strong. That's why I was wondering about the petcock. It almost seems like there is an air pocket and once I re prime everything seems OK. I know that I shouldnt have to re-prime daily when I go to start it.
 
I'd ditch the filter. If you have crud in the gas tank clean it properly. In many cases the filter restricts fuel flow and forces the fuel line to make a loop which restricts the fuel further. The only filter on the bike when it left the factory was in the petcock and on the float needles (maybe).
 
Yes the air box and filter are installed and sealed properly. The only reason I put an in-line filter on was to make sure that there was no gunk flowing into the carbs right after a cleaning. I will put a new vaccuum line on today and pull the filter to see what happens.
Someone mentioned setting the idle circuit using a max idle method? Can you steer me to a link that describes that?
 
GTGS said:
Plug color is perfect on 1,3,4 # 2 is rich.
Click to expand...
the usual reason for the No 2 plug showing a rich running condition, is a leaking petcock diaphragm.

replace your vacuum hose, then try running it with the vacuum line connected to the pectcock in the normal fashion and see how it runs. then try it with the vacuum line disconnected from the petcock, the line plugged off so there are no vacuum leaks and turn the petcock to the prime position.

does it still go "Bahhhhhaaaa' and fall on it's face?
 
Well I got to try a few things today. I put on a new vacuum hose and removed the extra filter. Same issues on start up. It's a very cold day in new york but I let it warm up and made a few passes down the street. It ran good initially but then started to stumble. I stopped at the end of the street and put it on prime and waited a minute and it ran good. I switched it over to run and after a minute or two it stumbled again. I let it cool then went back out a few minutes ago and pulled the vacuum line from the tank and plugged it. Put it on prime and fired it up. This time it never went Baaaaaa and kept running well. Sounds like the Petcock diaphram is the culprit.

Should I buy a new diaphram, a kit, or an OEM from Bike Bandit?
 
GTGS said:
Put it on prime and fired it up. This time it never went Baaaaaa and kept running well. Sounds like the Petcock diaphram is the culprit.

Should I buy a new diaphram, a kit, or an OEM from Bike Bandit?
Click to expand...
As I suspected...

you should buy an OEM petcock, but not necessarily from Bike bandit. double check the prices from PartShark or Carolina cycles. you could also, if you would like, choose to spend a little more buying it local.

see Steves excellent sources list.
http://www.thegsresources.com/_forum/showpost.php?p=1128505&postcount=4
 
Last edited:
rustybronco said:
... see Steves excellent sources list.
http://www.thegsresources.com/_forum/showpost.php?p=1128505&postcount=4
Click to expand...
:oops:

I have just collected all the suggestions as others have posted them.

There are times when I am going to do some major shopping, like a few weeks ago, when I started working on "Freebie", where I will actually start a spreadsheet and compare prices between all the vendors. At that time, I did not have Cycle Parts Nation in my list. Only comparing the vendors that had ALL of the parts I was looking for, it was close between Babbitts and PartShark. Babbitts actually had better prices most of the time, but I was getting a LOT of small stuff, and Babbitts' policy of a $2.97 minimum ended up raising the bottom line. I have not bothered to go back and add Cycle Parts Nation to the list to see how much more I might have saved, but a spot check on some other parts show that they are even cheaper than Babbitt's and PartShark. Will have to order something some time to see how the service is.

.
 
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