Rough idle followed by no start after oil change.

[Zack]

This would be a good time to check petcock for correct operation- so you can rule it out as a problem and move on to carbs. Disconnect fuel line at petcock - in "ON" or "RES" no fuel should flow or dribble if engine ain't running.

It doesnt flow unless its on the one across from RES, at which point it gushes.

EDIT
I took the battery to the auto store and they said it was down a volt, Im assuming this was the problem, and desperately hoping.
I can go pick it up in 30 minutes.

[Zack]

Bike turns over better now but WILL NOT START...
Spark plugs are not wet so its not getting fuel where it needs to go.

There is a second line that was never hooked up to the petcock, I never needed it before, would I now?
I dont know what to do at this point, does anyone?

[Dogma]

A second line? There's the main fuel line that goes to the T between #1 and #2 carbs. The second line is a smaller vacuum line that goes from the petcock to a nipple on the front side of the #2 carb. The vacuum opens the petcock when in the run position, and a spring in the petcock automatically closes it when the engine stops. Without this line, it will only run on prime, and #2 carb will have an enormous vacuum leak (unless it's been capped). Running on prime risks overflowing the carbs if the needle valves don't hold.

Original petcocks have often failed by 34 years of age, and rebuild kits don't often work. Sometimes if it doesn't work properly, a disassembly and cleaning can get them working again.

Proper functioning of that petcock is this: On prime, fuel should flow freely. On the run (on?) or reserve setting, it should only flow when there is a vacuum on the smaller nipple. Gas should never come through the vacuum side, and shouldn't even drip when set to on or reserve.

[Zack]

Well I seem to have isolated my problem, no fuel is getting to the carb.
I just put my lines back on and left the bowel drains open and nothing ever came out. With the line off gas will pour out the petcock, but it doesnt get through the carb.

[mrbill5491]

Umm, the main fuel line T is between carbs #3 and #2. Are you running an inline fuel filter?

[jbthomp]

So what your saying is when you first pulled the bowl drains it had fuel in it but now they won't refill correct? If that is true you either have a pinched fuel line between the tanks and the carbs or something stuck in the line somewhere. If you are getting fuel to two of the carbs but not the other two the problem is most likely in the carbs themselves. You do have the fuel line hooked up to the correct place on the carbs right? There are two vent lines for the bowls they are between #1 & 2 carbs and #3 & 4. The fuel inlet is between #2 & 3 carbs on the airbox side of the carbs. That is where the fuel line hooks up.

[Zack]

main fuel line is off, and not clogged but the T it goes into is very dirty looking into it with a flashlight.
How might I take it off so I can clean it?
ALSO, the float pins are all being very stubborn and will not come out so I can check the float pendulum hole thingy.

[jbthomp]

You probably found your problem. You have to ungang the carbs to get the fuel "T" out. If it hasn't been done recently it would be a VERY good idea to strip the carbs and dip them in carb cleaner for 24 hours. Blow out all the passages with compressed air and follow that up with all new orings.

You have to be very careful with the float pins because the little cast posts on the carb body break very easily. What i do is put a small socket on the side of the pin that has the flange on it and put it down on a table to get some support on the bottom post. Then tap VERY VERY carefully on the other side with a small roll pin punch and a hammer. Once it starts to move out you can grab it with a pair of pliers and pull it out the rest of the way.

[Zack]

Ungang them, I was afraid of that.. Are there any good youtube videos of that? I mean I have the bowels, slides etc all out but the carbs look pretty well "ganged".
I managed to get one pin out by using a dike, going to have to use my impact driver when people arent sleeping for the float screw, its stupid tight like most else.
I was hoping to just go heavy with the carb cleaner in the "T" and then hit it with air once its soaked and I have the floats all off, is that reasonable or worth the effort or am I going to have to ungang them 0_0
Ive come this far on youtube and prior dirt bike carb knowledge lol

[cowboyup3371]

You cannot take shortcuts; there are passages you cannot see that can become clogged and cause you problems. Go to Basscliff's site (http://members.dslextreme.com/users/bikecliff) and download the carb rebuilding tutorial by Nessism. Follow his step by step instructions to the letter or you will have to do it again. Get new orings from www.cycleorings.com and bowl gaskets from Z1; I would also replace the screws with allen headed ones.

[Zack]

This is excellent http://www.mtsac.edu/~cliff/storage/...d_Tutorial.pdf
Thank you.
Ill be unganging them after work today, I remain confident in my ability to put humpty dumpty back together again.
All those years of Legos trained me for this hahaha

[Dogma]

Umm, the main fuel line T is between carbs #3 and #2. Are you running an inline fuel filter?

Well, I'm just full of typos this thread.

[jbthomp]

Here is some you tube videos if that will help.

https://www.youtube.com/watch?v=MdfH_kodoSU

https://www.youtube.com/watch?v=HrfV0kN1AQA

https://www.youtube.com/watch?v=Z4VJHvqB9F0

It is a 3 part series and they do a great job of explaining the process. They take them all the way down to the bare core but you don't have to remove the throttle shafts if you don't feel comfortable. Most guys here just leave the throttle shafts and butterfly's in and remove everything else and dip them in carb cleaner.

Your going to wanna get a couple cans of aerosol carb cleaner and a gallon can of carb dip. You will also need some source of compressed air to blow through all the passages with. If you don't have an air compressor those cans of electronics duster like for your computer work just as well. Just take your time and do it right and you will be fine.

[greg78gs750]

unless i am misunderstanding something, you did NOT have the vacuum line connected from the carbs to the petcock. this line is needed to make the fuel flow in the "on" position, which would explain why the carbs were dry....yes, you probably need to clean the carbs, but dont overlook something obvious and easy.

[850 Combat]

A 1980 850G that runs perfectly will not start from cold without choke. At least not within a reasonable amount of cranking. Without the choke cable, you can pull the choke rod on the carbs to the left, and hold it. You may be able to put a clothes pin on it.

Your petcock has two connections. That means that you need to connect two connections. The smaller one is engine vacuum, which opens the valve. The other is the fuel flow. Fuel should still flow when you have the petcock on prime, but when you leave the vacuum connection off, it isa giant vacuum leak, which isn't good ever.

If this bike has been sitting without being stored with the carbs drained, you will have to clean them internally, including the emulsion tubes and all of the tiny internal passages. There isn't any debate about that.