Fuel Delivery Questions

[Beemer]

GS 1000L
The upper hole seems to be closed off.
The lower hole is open.

Is this piece of plastic in the holes fixed or is it supposed to turn to create flow from one, or the other or both, or close off? It doesn't move when I flip the lever back and forth.

I'm working towards cleaning the carbs next weekend. I'm starting at the pet cock and working backwards to the carbs.

There's an inline filter of some sort on the gas line. Is this necessary?

I'm trying to work out a problem of a lack of power and a studdering. It seems the bowls aren't being replenished. What would be the next component after the fuel line that could create a restriction to the bowls?

Yesterdays events:
Setup the timing and gapped the plugs.
Started the bike.
Lots of revs finally. Thought I had the problem fixed with the timing setup.
Lots of oil smoke out of the left pipe that took a few minutes to clear up.
After 5 minutes of test riding & great power, the loss of power returned.
Took it easy going home.

Any thoughts?

[arveejay]

You have a petcock that is set in the prime position and there is one hole that appears open. Turn the lever and note that the other hole should open. One half of white plastic is for reserve part of gas supply. It should only fit in one way. The lever should always point straight down in normal situation, it is marked on. Sound like it's sucking gas thru the diaphram in the petcock. With the lever pointing straight down you should put a vacuum to the smallest tube on the petcock and it should allow you to suck with no restriction on the bigger tube. Another guy used a baster and I think I will use one next time I need to do this. Squeeze the bulb, force it into the smaller hoes on the petcock and let go of the bulb. It should stay crushed, if it fills up with air the hose is bad or the diaphram is bad. This would cause raw fuel to enter carb number 2 and it would look like oil burning smoke, it would also foul a plug very fast and quit firing on that cylinder. If it holds a vacuum, try to suck through the larger hose, it should pull air easy. If it doesn't, the diaphram needs replaced. Perform this test several times and see if results repeat. If the white piece inside the petcock doesn't turn with the lever you have a problem with the petcock. The rebuild kits for the petcocks are inferior, if you won't buy a new petcock you will fight it forever. If you want factory petcock I use www.bikebandit.com .

[Beemer]

Thanks arveejay.

I took the lever off the petcock to re-examine behind the lever. The plastic slot is nothing more than a semi circle. I guess it jammed and someone with a strong hand turned it anyway and broke off the other side of the slot. One of the 2 pegs on the back of the lever is broken off as well.

So, one hole isn't enough to fuel the carbs I take it?

[arveejay]

If it is stuck in the run position and you never need to prime the bowls or switch to reserve you might get by, if it's not sucking fuel into number 2. You are really just creating a problem that won't go away. A new petcock will cost around 50-60 bucks, then never worry about it again. Cheapest route is, block off the vacuum tube from carb 2 and put an inline on/off valve in fuel line within reach. You can buy an on/off valve at lawn mower shop for $5.00. Just remember to turn it off when parking and turn it on when riding. I've done this many times while waiting for a new petcock to arrive.

[Beemer]

It's in the Primer position. Dang....

I take it the Primer position only offers a small amount of fuel and not a sufficient amount to ride. (Just for my understanding.)

[arveejay]

When in the prime position the fuel flow is wide open gravity feed downhill. If you have the slightest seepage in any of the 4 float valve (including around the sealing O Rings) or floats set slightly deep, it will over flow that carb with gas and it will run directly into that corresponding cylinder, past the piston rings and into the crank case, Not good at all. That's why I suggested the shut off valve.

[Beemer]

No smell of gas in the crank case luckily.

Will Prime allow me to run the bike as if in the On position?

Thanks for your help Bob. I appreciate it.

[arveejay]

It would probably supply an over abbundent amount of fuel, as in too much.

[Beemer]

OK. I finally have some time to work on my bike. I stated earlier that I thought the petcock was in the prime position. Now I figure that I have no way of knowing for sure other than it's stuck in either the prime or run position. I need an accurate answer.

Looking at my picture above and disregarding the lever since the inards are broken, the lower of the 2 holes is open for fuel travel.
The top hole is closed.

What position is this petcock stuck in?

[arveejay]

I'm not sure what position your petcock is stuck in. You can buy an inline on/off valve at a lawn mower shop for around $5.00

[Beemer]

Damn. Every time I look at this thing new info comes to light.

Res is forward.
On is Down.
Prime must be back but doesn't have a designation stamped on the clip.

The plastic piece that is stuck with one hole showing must be in the Res position, horizontal and forward.

Nothing fell out from behind the lever when I remove the clip holding it on so who ever discovered the petcock lever wasn't changing position must have "glued" the position at Res. This would make sense.

Moving on.

Starting to remove the carb’s from the bike and before I start loosening the carb's I inspected what I have to deal with. Nothing special. Used to rip out my carb’s all the time on my 77 and 81, 750 SuperSports rejetting for pipes and K&N's.

Sitting in the seat and reading #1 carb as being the extreme left, I found a hose leading to no where from the #4 carb. (See pic.) It's on the on the back aiming slightly up. The end was just resting on the air box, up and out of the way. Is this supposed to be hooked up to anything?

Confirm the arrangement of the hoses on the back of the carb,s please.

Carb #1 - Blanked on the body
Carb #2 - Hose leads to sending unit on tank
Carb #3 - Petcock vacuum hose
Carb #4 - Hose leading to nowhere

[bwringer]

I don't mean to be rude, but will you PLEASE go buy a freaking petcock already??????? It is no good. Get a new one and eliminate it as the source of your problem.

Petcocks do not last forever, but 20 years or so is pretty good. Every vintage bike on the road today has needed a new petcock at some point. Get a new one and then forget about it for another 20 years.

Also, remove the inline filter. Some have had good results with these, many have encountered problems -- it's very difficult to route the lines with no kinks and to ensure adequate fuel flow through the filter. Remove this from the equation for now.

Now then. On to the hoses. It sounds as if you do not have the petcock vacuum line hooked up.

There are two hoses that are the bowl vent lines. They simply route over the airbox (to keep water from entering the hoses) and are open to the air at the other end. These are usually plumbed into T fittings between the 2-3 and 3-4 carb bowls.

Another hose is the fuel line. It goes from the larger fitting on the petcock to a T fitting (normally metal) between the #2 and #3 carbs.

A fourth (smallest) hose is the vacuum line that operates the petcock. On CV carbs, this connects to the smaller nipple on the petcock and to another nipple on carb #2. On slide carbs, this vacuum nipple is on #3, I think.

There is often a drain hose connected to shield over the fuel sender unit on the gas tank. This is simply routed to the ground via some convenient path just in case the fuel sender decides to spring a leak. (So gas doesn't drip onto a hot engine.) This is not connected to the carbs or to the petcock. Many bikes have lost this hose at some point in the last 20 years.

Hope this helps!

[Beemer]

If it was as easy as going out and buying a petcock, I would have. Can't locate one so far.

I removed the inline filter as I've never had one on a bike to date.

There is often a drain hose connected to shield over the fuel sender unit on the gas tank. This is simply routed to the ground via some convenient path just in case the fuel sender decides to spring a leak.

My sending unit hose is presently leading to carb #2 vaccume nipple.

Sounds like this is wrong and needs no vaccume.

Is it important to have carb #2 vaccume line running to the petcock? or is a vaccume a vaccume?

Changed all the plugs, snipped the plug wires and re-inserted into the boots, Fast clean of the carbs (removed top and bottom bowls and covers and cleaned out the jets and needle holes), presuming the petcock is working in Run position and checked for vaccume. Put it all back together and went for a long ride.

I used Autosol on the blue of the pipes and it worked like a charm. Just a slight golden colour remains.

Slight adjustment on the timing and I think I have a bike.