Pro Rebuilt Carbs, New Plugs, New Petcock, New Vacuum line - starving for fuel

[Jenkin]

Hello all:

I have an 85 GS700e. A bit of background. It was running very strong a few months ago, however, started the annoying problem of dumping fuel into the airbox at an alarming rate. Looking into how to fix, I discovered several problems: 1) the carbs were not stock, and at this point I can't find anyone who can identify them; 2) the Petcock appeared largely useless as the vacuum line wasn't even hooked up to it - no idea how it was running; 3) the plugs were uniformly covered in serious black soot.

Because I really like the bike and its in good overall shape, and I couldn't do much with carbs I couldn't even identify and were wrong for the bike, I decided to do the following:

1) replaced the carbs with refurbished Mikuni BS32mm by WiredGeorge. They are from an older GS750. Jetted for air pods.

2) removed the airbox and installed EMGO air pods

3) replaced the Petcock with a K&L 18-4358 model, which claims to work on my bike (who knows)

4) replaced all the spark plugs with new NGK D8EA

5) replaced intake boot o-rings

6) replaced vacuum hose for petcock with OEM

Since that time, the bike is acting like it is absolutely starving for fuel. It starts well although I have to prime the carbs every single time, which may be a sign. It idles very strong and just purrs along beautifully at idle, and will rev strong. But as soon as I get on it to ride, I literally can barely move. It bogs down immediately. I'm lucky to get above 10 MPH and often have to stop and prime the carbs again.

I trust WiredGeorge's work and reputation; my sense is this is a petcock-to-bowl problem. Any thoughts out there? Should I just do my best to buy an OEM Petcock if I can find one? Thanks for any insight.

[allojohn]

Now you have the right carbs you should jet them for your bike.... put the airbox back on - you won't regret it....
Get yourself an OEM petcock, it's well known around here K&L bits are cr@p.

[Jenkin]

Thanks Mal - I should mention, the airbox that came with the bike was modified/cut/patched/messed-up significantly to accommodate for what I now know were the wrong carbs. I did ask that my refurb carbs be jetted for air pods when purchasing, I’m confident they have been. Seemed like a simpler solution if jetted properly but I imagine I could find many opinions about that here...

Thanks for your opinion on my aftermarket Petcock. Others agree with that as well?

[tom203]

Do the simple stuff first....test your petcock...in “on “ or “re” position no fuel should flow until vacuum is applied to petcock vacuum fitting : suck on it..you should see a good flow. Make sure your gas tank cap vent is not plugged and blocking fuel flow to bowls..leave cap loose and see if fuel flows better.

[slayer61]

I went through this a few years ago. My wife says

Did you check the fuel filter?

Of course I checked the fuel filter...






I checked it again when she wasn't looking & found it full of snot & nasty.

[Agemax]

Throw those crappy EMGO pod filters in the nearest trash can and buy some decent filters, APE or K&N.

[Jenkin]

Thanks all for the input. I acknowledge I have some budget choices of parts (K&L Petcock and EMGO filters) but unless either is a total failure, it doesn’t seem like either would be the sole cause of a total loss and gas starvation under load. As a troubleshooting step, I put on a clear fuel hose to see what was happening with the fuel. When the petcock is on, fuel is going into the hose and the hose fills up. However, there’s also an air bubble at the top of the hose which doesn’t make a lot of sense.

I wonder if I have a challenge with vacuum forming in the fuel bowls? Perhaps it isn’t venting properly, and the bowls aren’t filling quickly enough to supply fuel. That may also explain the air bubble I’m seeing in the fuel hose? Just thinking out loud -

[Big T]

Break out the duct tape and tape over half the surface of the pods.

[Big T]

Break out the duct tape and tape over half the surface of the pods.

If it improves, the jetting is wrong

[Steve]

I wonder if I have a challenge with vacuum forming in the fuel bowls? Perhaps it isn’t venting properly, and the bowls aren’t filling quickly enough to supply fuel. That may also explain the air bubble I’m seeing in the fuel hose? Just thinking out loud -

It might not be vacuum, it could be PRESSURE in the bowls.

Along that line of thought, what is the status of the carb vents? A surprising number of new owners don't understand where all the hoses go, and frequently get them wrong.

.

[Nessism]

Break out the duct tape and tape over half the surface of the pods.

If the bike runs better after doing this you will then know the jetting is off.

[rphillips]

Hey Jenkin, I sent you have a private message.

[Jenkin]

Steve - thanks for the response. These are just simply vents between bowls 1-2 and 3-4. Ideally one could attach hoses and take them up over the swing arm, but for now they are just open and between the carbs bowls. “Should” be venting fine.

[Jenkin]

Thanks - yep, checked the fuel filter, very clean (which I’d expect with a brand new petcock)

I went through this a few years ago. My wife says







Of course I checked the fuel filter...






I checked it again when she wasn't looking & found it full of snot & nasty.

[Jenkin]

Thanks - yes, tried the above. Petcock is working well and tried venting the gas cap. Replied to an earlier post that I put a clear fuel line on for troubleshooting and fuel is always in the line, so I’m thinking the petcock is doing OK so far. Problem continues even after I prime the carbs for a few seconds to fill them up.

Do the simple stuff first....test your petcock...in “on “ or “re” position no fuel should flow until vacuum is applied to petcock vacuum fitting : suck on it..you should see a good flow. Make sure your gas tank cap vent is not plugged and blocking fuel flow to bowls..leave cap loose and see if fuel flows better.