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rebuilt carbs and still running problems

  • Thread starter Thread starter denton550
  • Start date Start date
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denton550

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just rebuilt the carbs on my 1981 gs550T, new gaskets and o-rings and plugs and dipped for 24 hours, the idle screw is broke, but that dosent explain why carb #2 is leaking gas, i have reset the float height and im at my wits end, any ideas?
 
Hi,

How's your petcock?


Thank you for your indulgence,

BassCliff
 
As Cliff alludes, if the petcock has failed there may be fuel back-flowing down the vacuum line and into #2 carb. A piece of clear tubing in place of the vacuum line should tell the tale. If this is not the case, then your float needle is not sealing. There are various possible reasons but you need to take the carbs back off and figure out what's wrong.
 
denton550 said:
I have no vacuum line, would that be a problem?
Click to expand...

That would be a different problem.

Your float needles are probably leaking and failing to cut off fuel when the bowl fills.

Here is the saga from my overflowing carb adventures.
 
For normal operation, the petcock requires vacuum in order to flow. The vacuum line runs from the #2 carb to the petcock. With the petcock set to the Prime position fuel will flow without vacuum, but that position is not intended for normal use since the fuel will continue to put pressure on the float needles even when the engine is turned off.

A fresh and clean float needle and seat should be able to hold back the fuel even when the petcock is set to Prime. In the reality of old parts though that's a tall order. I suspect your #2 carb float needle and seat is not performing like it should. This is often the case with old carbs, particularly if the little spring in the float needle has lost it's springiness. With the petcock on Prime, and fuel allowed to flow all the time, some incremental seepage gets past the float needle and before you know it the carb is leaking fuel.

My suggestion is to check the petcock to make sure it functions properly: fuel should not flow when set to the ON or Res position unless vacuum is pulling at the port. When fuel does flow none should be going down the vacuum line. The vacuum line must be hooked up otherwise the petcock won't work right and there will be a massive vacuum leak which causes a host of different issues.

Next, check the function of #2's float needle and seat. It should be strong enough to hold back the fuel when the petcock is flowing fuel and the float bowl is full. It there is leakage replace the parts as required. I advise you to make a fuel level gauge and check the fuel height properly, that way you will know for sure if the float needle is working properly.

Hope this helps and good luck
 
I trimmed the gasket down because I believe it was rubbing against the float, I believe it did the trick. I filled it up with gas and no more leaks! Now I just need to tune the carbs, get a new idle screw and air box cover
 
OK, re-re-rebuilt the carbs, checked all the float heights (22mm) and set all the air screws to 2 1/2 turns out, installed the carbs with fresh idle screw, sealed boots ( air and engine side) new o-rings, everything has been dipped and cleaned, new gaskets, checked all ports and holes in the carbs for crud, cleaned and did everything by the book, go to start it up, and nothing, if i play with the choke i get a stutter like her is going to start but still nothing, what am i doing wrong? the ignition and spark plugs are fine and its getting plenty of gas, petcock is ok too. any ideas? should i try the air screws at 3 turns out? shim the needles? the bike is completely STOCK, everything is OEM. even got my air filter cover on too. i just want it to start at this point :(
 
I got her running, once i adjusted the air screws to 2 1/2 turns out, i heard a little bit of life, however the battery was dead, so after a quick charge, i plug it back in and tried again, this time i did full choke and after a small struggle i opened the throttle and held it, tuned the idle a bit to keep her from dying and its been running since. now to sync the carbs and personalize the bike. thanks for all the help guys
 
denton550 said:
I got her running, once i adjusted the air screws to 2 1/2 turns out, i heard a little bit of life, however the battery was dead, so after a quick charge, i plug it back in and tried again, this time i did full choke and after a small struggle i opened the throttle and held it, tuned the idle a bit to keep her from dying and its been running since. now to sync the carbs and personalize the bike. thanks for all the help guys
Click to expand...
Nicely done.

Have you done a valve adjustment? The carb synch should be done after that. There's no harm in doing it before the valve adjustment, but you'll have to repeat the job when you do the valves.

I'm a little concerned by your use of the phrase "quick charge". What do you mean by that? These little batteries shouldn't be charged up at much more than 1.5 amps. Be careful here as it's pretty easy to fry a battery on a car charger.
 
i have not done a valve adjustment, i do not have the confidence to go digging in the engine like that
 
denton550 said:
i have not done a valve adjustment, i do not have the confidence to go digging in the engine like that
Click to expand...

If you don't adjust the valves they will burn and you will be walking.:mad:
 
Denton, do you have any kind of a camera - digital or phone? If so, take pictures of every step you take and upload them to your computer. If you are unsure about something come on here and ask or search through the archives; you are not on uncharted territory. If you get lost about the order of parts, look online at the parts fiche - it shows everything you need to know.
 
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