Fuel issues

I have a 1985 xj700 . 2 of my carb bowls are full and 2 are empty. The extra fuel is being pushed into the cylinders

 

Petcock vacuum not working so constant flow of gas, not good but not a direct problem if the rest is ok but clearly it's not. Stuck floats or a valve pin not closing properly on the valve seat. Saying this it is strange that 2 bowls are empty, looks like those are not getting fuel at all. After fixing you have to change your engine oil, is it more than full when you check the sight glass?

 

The 2 bowls closet to the petcock are full but the other 2 are bone dry

 

The fuel supply is in between carb 2 and 3. Looks like the float of carb 3 is stuck closed so no fuel can enter. Did you try tapping the bowl of carb 3 to see if the float comes free?

 

air head or watercooled?
what have you done to the carbs to clean?

 

Air head. I took carb rack off and cleaned it and still nothing

 

If you pulled rack , remove the float bowl , pull pin on float and pull float needle , check tip if it is rubber see if it is still pliable. If it is stiff or grooved it should be replaced. The other thing to check while float is out , remove the seat using a 10 mm socket , check the screen it could be plugged.

 

Are you on the center stand? Is your petcock set on PRI?

if you get fuel to two carbs on one side but not the other side, you have fuel flowing, but you have either

1. A blockage in the right side of the fuel T or the carb body inlet

2. Both fuel valves are stuck shut

 

^^^ blockage I have found more than one carb set with build up where the fuel tube connect into the carb bodies

 

I blew the lines out with an air hose but still nothing

 

Thanks everyone for your inputs. Sounds like I just need to rebuild them.

 

What exactly todo you mean by that?
The overflow lines? They’re always open anyway
They fuel line? How do you know air went through all 4 fuel valves?

if compressed air DOES go through all 4, but fuel doesn’t, then your floats are closing too quickly then not allowing any more fuel to flow...... either floats are wrong or needles stick. Make sure you didn’t put a couple floats in upside down. It wouldn’t be the first time I’ve seen that.....

also not sure what you mean by “2 are empty— the extra fuel is being pushed into the cylinders”.....

1.fuel doesn’t get pushed...we don’t have a fuel pump.
2.if the fuel is going to those cylinders, it MUST go through the bowl to get there.
3. If you mean the gas goes through but doesn’t FILL the bowl, then your float levels are way off

 

All I can get my bike to do is back fire

 

Check to make sure you have the spark plug caps on the right spark plugs one coil is for one and four the other ignition coil is for two and three. Why it should be labeled or the longest ones go to the outside shortest ones go to the inside cylinders.
The next step would be to home out your ignition system to see if everything is in spec. Does it backfire when you let off of the starter button or while cranking.
Tell us what you've done to the bike so far carb cleaning etc.
It could also be that the primary connectors to the ignition coils are reversed coil pack one connection is on coil pack too..
Do you still have the glass fuses? It could be just a bad connection at the fuse clips.
And what bike is it that you have.?
Have to confirming the ignition system is set in the spec you should start to look at fuel issues properly adjusted carbs probably cleaned carbs valve shims and spec

 

Do you have an existing thread about your bike? If so I'll move this post to it.
History matters.

 

Existing thread:
https://www.xjbikes.com/forums/threads/fuel-issues.129972/

 

Yes that is my post

 

I have a 1985 xj700 . The bike ran great I took off tank and fenders to have them painted. Changed throttle cable and plugs . When I got the parts back I put it together and it won't run... so far I have taken the carb apart to clean it cause I thought maybe some gunk got through the tank from being painted. All it will do is back fire. Plenty of fuel now and spark . It has back fires through carb a couple times but not like it has through the exhaust.

 

Where are you located in Indiana?

 

......

 

Merged.

 

Jetfixer is a good tech (there is a hint at how good in his username). It's common here for members to offer in-person help when possible.

When you say that you cleaned the carbs; what exactly did you do, and how did you do it?

 

This is my first motorcycle so I'm not 100% on knowing what im doing. I took bowels off , main jets, idle jets, baffles, cleaned everything with carb cleaner and brushes, cleaned floats and float pin , I blew compressed air through main gas line to make sure all passages were clear . Reassembled... The plugs are getting fuel and I have spark. Sometimes its a loud boom other times its real muffled . I've tried starting fluid in all carbs but it backfires through carb and catches fire. I have brand new plugs. Checked all for spark made sure wires were in correct order.

 

Jeremy1232 Have you done a bench sync? and a carb sync? I'd refer to the " Church of Clean" Post if I were you. Good place to start anyway.

 

What is the order you have the wires in? Yes I know you said you have them in the correct order, but what if you actually have them mixed up and don’t know it.....

 

Sounds like a rebuild is in order. If you haven’t torn the carbs down this far, your haven rebuilt them.