86 GS450: Fuel in the Airbox Question

[pnwesside31]

Well, I'm still chugging along on this project, and slowly but surely I'm learning....anyway, my question is about fuel in the airbox.

Basically, I tried to fire up the bike, and it would turn over here and there, but there's an issue with fuel getting to the engine. I accidentally left the fuel in the prime position, and when I got back to the bike, I noticed fuel dripping consistently out of the overflow valve? that points directly to the floor. After I realized that, I turned the fuel to the correct position to stop the leaking. I know I had fuel delivery issues this whole time, and I thought the carbs weren't getting any fuel or any fuel to the engine, but I'm assuming the fuel is getting to the carbs now because the airbox had fuel it was draining, so why wouldn't it get to the engine consistently?

Thanks to all who've helped me get this far. I'm hoping to finally get this thing going.

[Steve]

OK, we have a few things to clarify before we can get down to solid answers.

... I accidentally left the fuel in the prime position, and when I got back to the bike, I noticed fuel dripping consistently out of the overflow valve? that points directly to the floor. ...

To the best of my knowledge, your bike does not have an "overlfow valve". Exactly where is this device you are talking about?

I know I had fuel delivery issues this whole time, and I thought the carbs weren't getting any fuel or any fuel to the engine, ...

I looked back at some of your first posts and saw that you had fuel delivery problems back then. I did not bother to read what all has happened in the last 10 months. Did you ever get the bike running? You mentioned several months ago that you had "cleaned the carbs". How did you do that? If you merely sprayed some cleaner around at the parts you could see, that's not nearly enough. The carbs must be dismantled and dipped, then re-assembled with new o-rings.

... but I'm assuming the fuel is getting to the carbs now because the airbox had fuel it was draining, so why wouldn't it get to the engine consistently? ...

Maybe because the carbs are not clean?

Also, if your valves are not properly adjusted, the engine can spit back through the carbs, taking the fuel mixture back into the airbox. If this happens often enough, gas will accumulate there.


Hope this helps, it sounds like you have been fighting this for quite a while.

.

[pnwesside31]

Thanks for the note. I actually got the bike running for a good week. That was the best week of my summer. And then after that week, same issue. The engine just wasn't getting consistent fuel flow. Here's what I know...

Overflow valve off the airbox: It's located at the bottom center rear of the airbox. It's in between the airbox and the rear tire, and the overflow flows through a small straight pipe down to the ground. I guess it's more like an overflow hose more than a valve.

Cleaning of the carbs: I basically got it cleaned (dipped) and looked at 3 different times. I'm not sure if they replaced the rings, but to be safe, I was going to do it a 4th time. I was basically going to replace the gaskets and needles, as well as spray it down with carb cleaner. I tried to find a rebuild kit for these carbs, but the shops around here (portland, or) don't have any.

Valve adjustment: Haven't even gone down that road. I'm hoping the above takes care of everything.

[BassCliff]

Hi,

I found some notes on overflowing carbs and other stuff on some guys website. It might help.

Overflowing Carbs

Carb Specs:Float Height/Jetting/Cleaning

Carb Notes (sync, etc)

Thank you for your indulgence,

BassCliff

[GER144]

You are going to have to go through your carbs again. Make sure the float needles are clean and in good shape, (not grooved/worn), if your float needle seats are removable and have o-rings around them they need to be replaced. These float seat o-rings are a very common place for fuel leakage. After the carbs are done again, bench test them to make sure they do not leak. Hook up a remote fuel supply to the carbs and see if they hold.

Even if you left the bike's fuel tap on 'prime', if the float needles/seats/o-rings are in good shape, there should be no leakage into the air box.

As for fuel delivery problems, maybe it is time to replace the fuel tap. Or rebuild it, if there is a kit available. (K&L kit?). Also check the vacuum line to the tap to make sure it is not cracked broken, etc. The fuel tap and vacuum line can cause fuel delivery issues. Good idea to remove the tap completely and check the filter screen, as it may be plugged with crap too.

[Steve]

Skip the carb kits. Period. They often contain parts that are of sub-standard quality and don't contain all the parts you need, anyway.

If you are going to do the carbs yourself (you really should), get a can of Berryman's or Gunk carb cleaner dip. It is a gallon-size can that has about 3 quarts of liquid in it, along with a basket to hold the parts. That will cost less than one carb kit. Get a set of o-rings from cycleorings.com. See if he has the intake o-rings, too. Eventually, you will need a device to sync your carbs. With only two carbs, your options are greater, but since you might later upgrade to a multi-cylinder bike, go ahead and get a gauge set now that will handle it. The best is about $95, the others range from about $50 to $90. With only two carbs, it will take half the time to do your carbs, figure on a total of three days. (The rest of us require five.)

When cleaning (dipping) the carbs, do not skip any steps. Any steps you skip you will have to come back and do later, but you won't notice it until you have the carbs on the bike and can't figure out why it's not running right.

.

[pnwesside31]

Dumb question..........what is a fuel tap, and where is it?

[BassCliff]

Hi,

Fuel tap = petcock.

On the left side, rear, bottom of the tank, next to your left thigh.


Thank you for your indulgence,

BassCliff

[pnwesside31]

Got it.....I rebuilt that already.

[KitKat]

rebuilding an old petcock might not work. purchase a new one from partshark.com or some other place, then your good for another 20 years

[pnwesside31]

couldn't find anything on partshark.com. Do you recommend any other sites?

[terrylee]

Try bike bandit or cheapestcycleparts.com terrylee

[pnwesside31]

Thanks for the websites. Just want to make sure I need a completely new petcock vs my rebuilt one. I actually tested it, and this is what I got:

Reserve Position: No gas
On Position: No gas
Prime Position: Steady Gas Flow

As far as the carbs go, I started taking them apart to rebuild eventhough they don't make rebuild kits for these carbs any more. I called the local (Portland, OR) Shop and they said all I could buy is float bowl gaskets, float needles, and as I take my carbs apart and find O-rings, just bring em by and they should have them.

Is this all I could do?
Is this all I NEED to do?
How do I know if I should replace something, or if it's still good?

So many questions, so little time. Thanks for your help.

[Steve]

I actually tested it, and this is what I got:

Reserve Position: No gas
On Position: No gas
Prime Position: Steady Gas Flow
...

One more test: in the Reserve and ON positions, apply a little vacuum (suck on a hose), you should have gas flow.

As far as the carbs go, I started taking them apart to rebuild eventhough they don't make rebuild kits for these carbs any more. I called the local (Portland, OR) Shop and they said all I could buy is float bowl gaskets, float needles, and as I take my carbs apart and find O-rings, just bring em by and they should have them.

Is this all I could do?
Is this all I NEED to do?
How do I know if I should replace something, or if it's still good?

So many questions, so little time. Thanks for your help.

No, that's not all you can or should do. Get a full set of o-rings from cycleorings.com. The owner there is a member of this forum and had put together kits with ALL the o-rings you will need.

.

[pnwesside31]

Thanks for the quick response. Which hose do I suck on?