Fuel flow?

[Downer]

Ok so I pulled the drain screw out on both carbs and on a previous thread someone told me that with the petcock on fuel should flow but nothing is coming out of the drain thought maybe it was the gas cap being air tight but no and I ran all new fuel lines with inline fuel filter anybody have any ideas to get this fuel flowing again?

 

[tx650]

Is yr fuel delivery via vacuum or str8 thru?

 

[Downer]

Straight through

 

[tx650]

Might be the filter in the actual petcock could be a blockege?

 

[jamesgs4]

does your petcock have a "prime" or "pri" setting? try that one.

 

[Downer]

Ok so if I were to blow into the fuel lines through to the carbs should there be pressure? Or should it just blow through cause right now it's got pressure and won't go straight through

 

[xjwmx]

If you hold the carbs upside down so that the float valves are seated it'll block air. Right side up, no. To see if your petcock is working take the hose off of the petcock and see what happens. If everything is right and your petcock isn't vacuum type fuel should flow out of the drains with the drain screws out because it keeps the float valves low enough to not seal. Could be old sediment in the area of the drains plugging them up. Sediment tends to settle around there.

 

[Downer]

Ok dropped the bowls and on the right side the float was stuck in the closed position tapped it once and everything was fine so I'm guessing the float needle was stuck now I guess I'll just have to tap on the bowls every once in awhile

 

[gentlemanjim]

Why not clean them properly or replace the needle and seats very cheap?

 

[Downer]

I did clean them but will replace next time I order from mikes

 

[XSLeo]

Take the cotton off the end of a q-tip, wrap a bit of 40 steel wool around the end of the q-tip . Use this with a bit of carb cleaner to clean the seat of the float valve. This cleans out the crud and polishes the valve seat to just like new. You can do this with the carbs on the bike. Remove the bowls and float, don't lose the needle.
A very close inspection of the needle may reveal that the needle has a groove around it where it seats in the valve. This won't seal well.
I have read that the viton tipped needles like used in the BS34 carbs will work with the earlier BS38 valves. It may be worth checking into. The Viton tip should seal better than the steel tip of the regular needle.

 

[xjwmx]

His description is they're sealing too well, not inadequately It's hanging closed. What would cause that?

 

[jamesgs4]

crud in the space where the needle is.

 

[xjwmx]

Naw, that would make it leak unless it was totally crudded closed Mayber a rusty hing pin or something. Some of the pics I've seen of the insides of carbs, I can't believe.

 

[jamesgs4]

thats what I mean, crudded closed. a stuck hinge pin would also make it stick open.

 

[Downer]

ok old thread kinda new delima anyways bike will run with the fuel thats in the lines and with a full fuel filter but after the line and filter go dry no more fuel will fill the lines and filter its not a petcock problem cause ive pulled the line and drained into a cup not a carb problem cause the bike will run through the fuel. now if i empty the fuel filter and line then turn on petcock it wont fill but if i squeeze the line then it slowly sux fuel into filter and line but thats the only way it will fill any ideason how i can get this fuel flowing? thanx

 

[jchrisk1]

Have you tried changing the fuel filters? Last time mine did that I changed them and it flowed again. It was doing it again at the end of the season last year so I will replace them again and see if that fixes it. I also have to clean the gas cap vent. I've ran mine down on reserve a few too many times and I think the filters are filling up with crap. If you find it is something else post up so I can check it out too.

 

[XSLeo]

With enough crud in on the float valve needle and seat they can stick closed as well as open.
On the carbs, If they are the stock 76-77 set up, there are float bowl vents up on the inside of the carbs. If they are inter connected the bowls can't vent. If the air can't get out fuel can't get in.
I think I have a pic of my 76-77 carb set. I'll post it up to show how the bowl vents had hoses running of the vents to below the carbs.

From between the carbs you see two clear hoses that run from up high on the carbs, and cross as they go down through loops at the corners of the carbs, to below the loops. These are vents. They need to be open to air.
Leo

 

[Downer]

That could be my problem cause I have just one tube connecting them both like the tube below but that's how I've seen all the carbs my buddys were set up the same way but I'll check it out

 

[jchrisk1]

My carbs are 78-79 and don't vent like that. I changed the filters and cleaned the carbs. When I first opened the petcocks they filled as normal. Then after a short time the left side is dry again. I tried opening my gas cap and that didn't help. I'm wondering if my petcocks might be dirty. I'll keep searching until I figure it out.