Need help with gs 850 fuel system

[jdvorchak]

Not sure which model used a 34mm petcock but I ended up with a Suzuki petcock, which was 34mm, on my KZ750 because all of the KZ petcocks I saw, on eBay, were 44mm. The tank was not the correct tank for the bike but it was what I had. I could be wrong on that. It was over a year ago. But the point is to be careful with his selection of a new petcock so he gets one that will fit first time. Especially since he doesn't know what model or year of the gas tank.

[Big T]

I dont know anything about a leverless petcock but you can simply check its operation by putting a 1/4 hose to the vacum side of the petcock and sucking. If the petcock is working gas will immediately start to flow from the fuel side of the petcock.

This

You guys are going on and on about replacing the petcock without even having it checked

1. Is there a vacuum hose that runs from the petcock to the top front of carb #2? If not, that's likely the cause
2. Boriqua is correct. Disconnect both hoses from the petcock, attach a hose to the vacuum port and suck on it. If gas flows, the petcock is good. If it doesn't flow, it's either clogged or faulty.
3. If no gas flows, drain the tank and remove the petcock. See if the fuel screen is clogged up

No RTV and get the correct gasket when you reinstall the old or new petcock. The bolts holding the petcock to the tank may have special washers with a seal



Post up some pictures of your tank and petcock

[Nessism]

This

You guys are going on and on about replacing the petcock without even having it checked

1. Is there a vacuum hose that runs from the petcock to the top front of carb #2? If not, that's likely the cause
2. Boriqua is correct. Disconnect both hoses from the petcock, attach a hose to the vacuum port and suck on it. If gas flows, the petcock is good. If it doesn't flow, it's either clogged or faulty.
3. If no gas flows, drain the tank and remove the petcock. See if the fuel screen is clogged up

No RTV and get the correct gasket when you reinstall the old or new petcock. The bolts holding the petcock to the tank may have special washers with a seal



Post up some pictures of your tank and petcock

One other thing...

When the slot in the petcock is horizontal that's the normal running position. Vertical slot is prime.

With the slot vertical pull a vacuum on the vacuum line and release. If the primer feature, and the check valve, is working fuel will flow. No fuel will flow until vacuum pulls the diaphragm open. If fuel stops flowing when the vacuum stops, and the slot is in the prime position, the check valve in the cover has failed.

[Redman]

mg,

Other conversation:

Is it running okay (now that you figured out the petcock)?
If not: Please describe "cleaned the carburators"....

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[Boriqua]

I will add something that is probably obvious but since there seems to be advice on what petcock you need for the year bike you have...

If you find that the petcock is faulty .. and mine was TRASHED .. just take a ruler with MM on it and measure the mounting screws center to center. Its bone simple and will remove any guessing. These are old bikes and you never know what tank might be on what bike.

[Machinegunner]

mg,

Other conversation:

Is it running okay (now that you figured out the petcock)?
If not: Please describe "cleaned the carburators"....

.

Haven’t received the petcock yet. Mine is the 50 mm. I tried putting gas via a funnel straight into the gas line but the battery died after about 10 seconds so I didn’t get it started. I checked for pressure on vacuum line and it was fine. I will update as soon as I receive the petcock.

By cleaning the carbs I mean complete disassembly, soaked in carb cleaner and jets checked for clogging.

[Cyrano]

Glad you went with a new petcock. I have the same model and had the same problems. I tried rebuilding the origianl and then went with a second hand unit and only got it right when I bought a new (50mm) part. Since then all has been good.

[Machinegunner]

Put the petcock in today. Found out the choke cable is broken 😠. Engine won’t start or run unless I hold the choke bar( not sure what it’s called) all the way to the left. Even then it runs very slow. Where is the carburetor (fuel or air) adjustment?

[Steve]

Engine won’t start or run unless I hold the choke bar( not sure what it’s called) all the way to the left. Even then it runs very slow. Where is the carburetor (fuel or air) adjustment?

It is quite normal to need the "choke" (it's actually an "enrichment system") to start the engine, especially when cold. To answer your question, I am going to refer to your first post and ask a question.

Hey, newbie here. Had a 1980 GS850L given to me. It had been sitting for 4 years. I cleaned the carburetors, ...

Exactly HOW did you "clean the carburetors? If you had cleaned them properly, you would know where the adjustment is for Idle speed, because it would have been removed in the process of cleaning the carbs.
But, to answer your question, the IDLE SPEED control is below the carbs, between #2 and #3.

If all you did was to drop the float bowls and clean them out, your bike will not run (well) until you clean the properly.

Click HERE to visit our library, also known as "BassCliff's site." You can download a manual for your bike and see tutorials for virtually anything you need to do to your bike.

Click HERE to see the tutorial for properly cleaning your carbs.

You may as well continue with some other maintenance that has likely been ignored, so click HERE for a tutorial on how to adjust your valves.

You will eventually need to check your charging system, too, but let's get the bike running first.

If the bike has been sitting for four years, I can probably guarantee that the tires and brakes were not changed just before the bike was parked, so they should be checked, too.

Yes, the list goes on and on, but when you are done, you will have a safe, reliable bike.

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[Machinegunner]

Wasn't asking for the idle adjustment. Is the single screw on the bottom of the float bowl the fuel adjustment? If so what is the factory setting?(how many turns out?) I might have tightened them all of the way when reassembling the carbs. I will post a video of it running as soon as I figure out how. Only runs with choke all the way out and if I rev it at all it cuts off.

[Machinegunner]

[Steve]

Wasn't asking for the idle adjustment. Is the single screw on the bottom of the float bowl the fuel adjustment? If so what is the factory setting?(how many turns out?) I might have tightened them all of the way when reassembling the carbs. I will post a video of it running as soon as I figure out how. Only runs with choke all the way out and if I rev it at all it cuts off.

OK, if you are not asking about the idle adjustment, the only other external adjustment is for pilot mixture. That is NOT the "single screw on the bottom of the float bowl", that is the drain screw that will empty the gas out of the bowl. They SHOULD be reasonably snug so they don't fall out.

The pilot adjustment (also known as the "mixture screw") is on the top of the outlet of the carb. If your carbs have never been worked on (quite likely), they are still sealed from the factory and not recognizable as such. If you do have access to the screws, turn them IN slowly, counting turns until they seat LIGHTLY, record the numbers. When I rebuild a set of carbs, I start with the screws out three full turns, knowing that they will need to be fine-tuned from there. They might end up about 2 to 2 1/2 turns out, but three turns provides a slightly richer mixture that lets it start easier for tuning.

Again, I have to ask, exactly how did you "clean the carbs"?

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[Machinegunner]

OK, if you are not asking about the idle adjustment, the only other external adjustment is for pilot mixture. That is NOT the "single screw on the bottom of the float bowl", that is the drain screw that will empty the gas out of the bowl. They SHOULD be reasonably snug so they don't fall out.

The pilot adjustment (also known as the "mixture screw") is on the top of the outlet of the carb. If your carbs have never been worked on (quite likely), they are still sealed from the factory and not recognizable as such. If you do have access to the screws, turn them IN slowly, counting turns until they seat LIGHTLY, record the numbers. When I rebuild a set of carbs, I start with the screws out three full turns, knowing that they will need to be fine-tuned from there. They might end up about 2 to 2 1/2 turns out, but three turns provides a slightly richer mixture that lets it start easier for tuning.

Again, I have to ask, exactly how did you "clean the carbs"?

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Took off float bowls and top took out jets and soaked. Drained the carbs last night and carbs 3 and 4 had no gas in them?

[Boriqua]

You mean when you initially took them off to clean the bowls had no gas? There is only two things I can think of.

one ..gas is not coming in because of a physical blockage where the fuel enters the carb. The gas line and the hole that allows gas into the carbs are fairly large but if there was a lot of rust in the tank .. I guess its possible to block it.

Second thought is there is no gas going in because of a mechanical failure. Your floats sit on a wee bitty pin that controls fuel flow. There is a name for it that escapes me now but if they are stuck in the closed position as if the float were at their maximum height just due to gunk and age then no gas. It works kind of like the float in your toilet to control how much gas lives in the bowl.

Edited to add
Soaking alone will NOT clean your carbs. Download one of the pdf's on cleaning. Dont ask me how I know
I Soaked, then sprayed all the passages with carb cleaner, The washed them in warm water with dish soap and then blew them out with a compressor.
Oh .. but I did not poke! So a few weeks later I was doing the whole damn thing again .. so poking is good.

[Nessism]

Carb rebuild tutorial linked in my signature. Might want to review again. Some of the questions being asked suggest that some steps were missed. Also check the newbie mistakes thread to see if anything applies. For example, it's critical to change the intake boot O-rings if you haven't already.

Again, the factory service manual details how the prime feature works with the leverless petcock. If no fuel is getting through to carb 3 and 4 that means that your float needles are stuck or you are not engaging the prime to fill the bowls.