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Petcock/fueltap issue?

  • Thread starter Thread starter m0ng00se
  • Start date Start date
M

m0ng00se

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Ok, I have a 79 GS850. Have only driven it home. During that drive there were serious issues with driving at hwy speeds. It would go for five or six miles then spit and sputter and die. Wait five or ten mins, open the choke, start her up and go. Five-six miles later the same thing. First thing I did was drain the gas tank and clean the fuel tap. Installed new hoses and filter for fuel line. I found a vacuum hose from the tap to the carb that was not connected. I replaced that. From reading some of the posts here, it sounds like the rest are vents or drains. Is this correct? I put a clear filter on so I can see the fuel moving through the line. While in PRI, I get a little bit of drip from the tap. After it has warmed up, I turn the tap to the ON position and the bike dies. No fuel flows to the filter. The vacuum line that attaches to the tap, produces a pulsating vacuum. Is this correct?
While inspecting the hoses, I found a crack by the mount screw on one of the boots that connect the carb to the cylinder. I can also hear a loud suction sound from here as well. I need to find these parts if anyone has recommendations on where to get them. I live on the Kitsap Peninsula in the state of WA.

For this model bike the Air box is in great shape for being plastic. Would it be better to upgrade to the K&N cones or keep the Air box?

Thank you for responding you folks have been a great help with my first bike.
Troy
 
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I think you've got it basically right. Here's what I've learned about this on mine: There should be a line from the tap on the #2 carb (from the left). The vacuum will pulse in time with the #2 cylinder's intake stroke. The fuel line goes to a T in between 2 and 3. The other two lines (between 1 & 2 and 3 & 4) are vents, and should be routed over the air box to hang in front of the rear tire. You can get the carb boots (intake pipes) for about $20 each from flat out. That's the best deal I've found, but you have to wait for them to do their thing. They're a little slow, and you may get your tracking number AFTER your parts. Be aware there are left and right hand boots, and don't forget the o-rings that go against the head.

The vaccuum petcocks on these can be a headache. Your filter may be making your flow problem worse. There isn't normally a filter there. On prime, you should get a good flow, not a drip, after cranking the engine to get some vacuum. On run you should not get flow unless the engine is running. Most around here recommend replacing the petcock vs rebuilding. I just ordered mine from Z1 Enterprises for about $40.

Replace the petcock and seal your vacuum leaks and you should be in good shape.
 
Your petcock already has a fuel screen on it!

In prime, make sure the arrow is facing towards prime, not reserve, you should get more than a drip out of it as Dogma has stated.

I went OEM and just installed mine a few nights ago.
 
ditto what has already been said. On prime you should get good solid flow, not a trickle. You might want to pull the petcock off and see if the filter is dirty. I had questions about mine but all the folks here recommend just replacing it. I did and am very happy with the results.

Before I had my vacuum line connected up I would run on the bike on PRI and move it to RUN when I parked. In that case RUN acted like OFF.

My 77 GS750 had pods when I bought it. If I had the stock air box I think I would leave it on the bike until I had it running perfectly. Once it was running really well I'd move to pods. That way as you tune for pods you know what you are shooting for. Just my 2 cents.

Good luck and keep us posted!

gbw
 
Thanks For the insight

Thanks For the insight

This is what I did. I pulled the tank, filled her up to about half full. I put the tap on PRI, the fuel drained out(I was able to drain a half tank in ten mins). I put the tap on RES and sucked on the vacuum hose(I got about a half cup of fuel), I got the same results for the ON position. While I had the tank off, I looked a little closer at the "boots" intake pipes and noticed that there appears to be a plastic covering over these. That is what is cracked. Is it possible the suction that I am hearing is from the air box not being sealed properly? While the tank was empty I looked inside of it. I noticed some miner patchy rust spots on the inside. The clear filter is still very clean so there isn't much flaking of metal or rust flakes. Would I be able to get away with a good cleaning and then sealer?

Again thank you for all that you folks have done. I hope to get to ride with some of you some day.
Troy
 
m0ng00se said:
This is what I did. I pulled the tank, filled her up to about half full. I put the tap on PRI, the fuel drained out(I was able to drain a half tank in ten mins). I put the tap on RES and sucked on the vacuum hose(I got about a half cup of fuel), I got the same results for the ON position. While I had the tank off, I looked a little closer at the "boots" intake pipes and noticed that there appears to be a plastic covering over these. That is what is cracked. Is it possible the suction that I am hearing is from the air box not being sealed properly? While the tank was empty I looked inside of it. I noticed some miner patchy rust spots on the inside. The clear filter is still very clean so there isn't much flaking of metal or rust flakes. Would I be able to get away with a good cleaning and then sealer?

Again thank you for all that you folks have done. I hope to get to ride with some of you some day.
Troy
Click to expand...

I don't know much about sealing the stock airbox or cleaning/sealing a tank, but if you search for those topics you will find a lot of info about each. There is even a thread about using electrolosis to clean a tank. http://www.thegsresources.com/_forum/showthread.php?t=106016&referrerid=9262

Good luck!
 
Funny you should mention Searching.

Funny you should mention Searching.

I have found a lot of useful info so far. I just don't want to be thought of as an inactive user. LOL
 
m0ng00se said:
I have found a lot of useful info so far. I just don't want to be thought of as an inactive user. LOL
Click to expand...

HA! I used to think that as well. My personal experience is the deeper I get into this bike the more "active" I become on the forum. And everyone here has been great about helping. Anything I have learned and can pass on is directly attributable to what I've learned here.
 
So Far...

So Far...

The tap is clean and working as it should. The tank has been cleaned out but not sealed. The fuel filter is cleaned. now is it possible that a fuel line could be to long? The fuel system in my understanding is gravity fed system. I Have noticed that the inlet to the filter sits higher than the outlet of the tap. Is it possible that this is preventing the fuel from flowing properly?

m0ng00se
 
If there's not enough rust to clog a filter, you don't need to seal the tank.
Is your gas cap vent functioning normally?
 
Gas Cap

Gas Cap

I am not sure how to test that. The gas flows out of the tap normally with the cap on. I can provide vacuum to the tap and it will allow about a half cup of fuel to flow from the ON position. Would this not happen if the vents are plugged? When I had the cap apart the vents holes were open(nothing stuck in them).
 
she's running like an old hag(and I couldn't be happier at this moment)

she's running like an old hag(and I couldn't be happier at this moment)

Finally my GS is running like a 79 GS should. 850 that is. I have not road tested her yet but she is purring like a cougar. I already can tell there are carb problems. I sprayed some starter fluid on the intake boots and instantly the idle smoothed right up. It was like this for all 4 intakes. No surprise considering it is 29 yrs old and never had the carbs off... Solution to the fuel delivery system; Small engine filter as an inline filter(not a fram car filter they are way to big.), Lined everything up so that fuel flows down to the carb(not over a hump in the hose), I also shortened the hoses by about three inches to compensate for the length of the filter. I also threw some seafoam into the tank to see if we can't clean the carbs out a little.
 
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thanks for the tip.

thanks for the tip.

Dogma,

Thanks for the tip on the intake pipes. Do you know what category they would be listed in? I think I am going blind and cannot see them in the pictures.

Thanks
Troy

Dogma said:
I think you've got it basically right. Here's what I've learned about this on mine: There should be a line from the tap on the #2 carb (from the left). The vacuum will pulse in time with the #2 cylinder's intake stroke. The fuel line goes to a T in between 2 and 3. The other two lines (between 1 & 2 and 3 & 4) are vents, and should be routed over the air box to hang in front of the rear tire. You can get the carb boots (intake pipes) for about $20 each from flat out. That's the best deal I've found, but you have to wait for them to do their thing. They're a little slow, and you may get your tracking number AFTER your parts. Be aware there are left and right hand boots, and don't forget the o-rings that go against the head.

The vaccuum petcocks on these can be a headache. Your filter may be making your flow problem worse. There isn't normally a filter there. On prime, you should get a good flow, not a drip, after cranking the engine to get some vacuum. On run you should not get flow unless the engine is running. Most around here recommend replacing the petcock vs rebuilding. I just ordered mine from Z1 Enterprises for about $40.

Replace the petcock and seal your vacuum leaks and you should be in good shape.
Click to expand...
 
m0ng00se said:
Dogma,

Thanks for the tip on the intake pipes. Do you know what category they would be listed in? I think I am going blind and cannot see them in the pictures.

Thanks
Troy
Click to expand...

On sites that use the Suzuki microfiche (flatout, bikebandit, etc.), the intake pipes are on the cylinder head. Your guess is as good as mine on any other sites.
 
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