Topic: Gas to carb problems.... or do I just not understand?

[vulture0027@gmail.com]

Having problems with my carburetors.... pulled them out....
- ran carb cleaner through slow jet & mainjet
- floats move freely

Before I pulled the carbs out, gas was draining from carbs #2 and #4
- after “cleaning” out said jets, I decided to hook the fuel line from the gas tank petcock to the carbs to see if each carb was getting gas...
-gas flowed through the left side but not the right side—
-took lines off the gas tank... petcocks both drained gas
-both gas lines looked clear
- I took the line on the right and blew air through it fine, blew through the line on the left and there was resistance....
- lifted the float on the one on the right and air went through....
-wft???-
Also: do I need to replace my fuel lines?... they look orangish/brown.

[bryanj]

Thats the wrong type of fuel line and definately needs changing for the correct type

[Deltarider]

Thats the wrong type of fuel line and definately needs changing for the correct type

+1
From my other post that I have just finished: What I have learned from experience, is that the CB500 and early models CB550 are very sensitive to have the correct fuel lines. If you have the standard petcock, length should be 18 and 30 cm resp. with an ideal internal ⌀ of 5,5 mm (outside ⌀ will be around 10 mm). If you have the newer model petcock (that hasn't the little bowl) length should be 17 and 28 cm resp. Route the fuellines correctly using for the  fuelline to carb 3 + 4 the little clamp you will find in the front of the carbs. Make sure this particular fuelline will not have an 'up and down' if you know what I mean, but will facilitate gravity to do its work unhindered. No extra inline fuelfilters. They'll bring nothing but trouble on these models.

[my name is nobody]

Having problems with my carburetors.... pulled them out....
- ran carb cleaner through slow jet & mainjet
- floats move freely

Before I pulled the carbs out, gas was draining from carbs #2 and #4
- after “cleaning” out said jets, I decided to hook the fuel line from the gas tank petcock to the carbs to see if each carb was getting gas...
-gas flowed through the left side but not the right side—
-took lines off the gas tank... petcocks both drained gas
-both gas lines looked clear
- I took the line on the right and blew air through it fine, blew through the line on the left and there was resistance....
- lifted the float on the one on the right and air went through....
-wft???-
Also: do I need to replace my fuel lines?... they look orangish/brown.

Petcock flow can be confusing. Each port serves a pair of carbs. By design, the petcock will
deliver fuel to the pair of carbs that needs it most. To check it for proper operation,
run a hose from each port to a drain jar....-
Turn the valve on, Block/restrict one of the hoses and leave the other
hose hang unrestricted... Fuel should flow freely and consistently from the unrestricted hose. Change sides
unblocking the first hose and restricting the opposite hose..Fuel should flow....
Finally, unblock both hoses and note flow. Under this condition, the valve, by design,
and gravity MAY cause the fuel flow to alternate between ports. This si to balance the fuel levels in each pair of carbs.

[evinrude7]

get rid of the inline fuel filters and try the test again.  are there an in-tank filters?

[TwoTired]

Do the float valves move freely in their holders?  There is no solid connection from float tang to valve for opening, only closing.

Cheers,

[vulture0027@gmail.com]

-float valves move freely
- no in-tank filter

.... just so that I’m reading you guys loud and clear...
I’m should take OUT the inline fuel filter so that there is NO filter between the gas tank and the carburetors, correct?

[TwoTired]

The stock fuel valve has a filter incorporated.  Extra inline filters are not desirable or necessary.

There should be a filter between fuel supply and carbs.  The stock one works well.

Cheers,

[vulture0027@gmail.com]

I will definitely change out the fuel line and get rid of the inline fuel filters....
evinrude and twotired- I think I misunderstood what you guys where saying , but I think I understand now... yes, I BELIEVE that the bike has the stock fuel valve with an incorporated filter... sorry, I’m a novice and I VERY MUCH appreciate your patience with me ....
I’ll report back with my findings (and hope that you guys are still on board to help this rookie out!)

[bryanj]

Yup, with a good fitting spanner on the hexagon on the bottom unscrew the bowl and inside is a filter and O ring.

[przjohn]

Having problems with my carburetors.... pulled them out....
- ran carb cleaner through slow jet & mainjet
- floats move freely

Before I pulled the carbs out, gas was draining from carbs #2 and #4
- after “cleaning” out said jets, I decided to hook the fuel line from the gas tank petcock to the carbs to see if each carb was getting gas...
-gas flowed through the left side but not the right side—
-took lines off the gas tank... petcocks both drained gas
-both gas lines looked clear
- I took the line on the right and blew air through it fine, blew through the line on the left and there was resistance....
- lifted the float on the one on the right and air went through....
-wft???-
Also: do I need to replace my fuel lines?... they look orangish/brown.

Petcock flow can be confusing. Each port serves a pair of carbs. By design, the petcock will
deliver fuel to the pair of carbs that needs it most. To check it for proper operation,
run a hose from each port to a drain jar....-
Turn the valve on, Block/restrict one of the hoses and leave the other
hose hang unrestricted... Fuel should flow freely and consistently from the unrestricted hose. Change sides
unblocking the first hose and restricting the opposite hose..Fuel should flow....
Finally, unblock both hoses and note flow. Under this condition, the valve, by design,
and gravity MAY cause the fuel flow to alternate between ports. This si to balance the fuel levels in each pair of carbs.

Huh?

Are you saying there is a balancing device inside these petcocks? I have never seen any device to regulate automatically the flow of fuel on these bikes except the float valves inside the individual carbs.

[Bodi]

Not a balance device, but fuel will often flow from one nipple and not the other if connected to open tubing. Just a weirdness of fluid flow with very low pressure, I guess. So if you hook up the carbs with no bowls to check fuel flow it's not unusual to get fuel coming from one or two only. Close those float valves and the fuel comes out of the other ones. In actual use, all the float valves are pretty much closed to let in just the amount of fuel the engine is using.

[my name is nobody]

Not a balance device, but fuel will often flow from one nipple and not the other if connected to open tubing. Just a weirdness of fluid flow with very low pressure, I guess. So if you hook up the carbs with no bowls to check fuel flow it's not unusual to get fuel coming from one or two only. Close those float valves and the fuel comes out of the other ones. In actual use, all the float valves are pretty much closed to let in just the amount of fuel the engine is using.

Yup, and if you don't know better, you end up chasing something that isn't a problem..
Don't ask how I know this It took me a while to figure it out.

[vulture0027@gmail.com]

ok MYNAMEISNOBODY....

-getting rid of the inline fuel filters
- got new fuel line
- hooked them up to the gas tank
- in the "on" position, NO gas flows from either gas line
- in the "reserve" position gas follows from one tube, but not the other. when i restrict (pinch the tube) of the gas line that is draining gas, gas follows from the side that it initially didn't drain gas from.

....i THINK i have at least 1.5 gals in the tank
is there something possibly obstructing the part of the tank that drains gas from the gas tank when it is in the "on" position?... if so, what's the proper way to clean the petcock of the gas tank?

[Deltarider]

Fill tank some more or at least tilt tank momentarily some 80 degrees to the left so the fuel that's in the right hand side of the tank will flow into the left hand side (where the petcock is). Then check again.

[przjohn]

Not a balance device, but fuel will often flow from one nipple and not the other if connected to open tubing. Just a weirdness of fluid flow with very low pressure, I guess. So if you hook up the carbs with no bowls to check fuel flow it's not unusual to get fuel coming from one or two only. Close those float valves and the fuel comes out of the other ones. In actual use, all the float valves are pretty much closed to let in just the amount of fuel the engine is using.

Yup, and if you don't know better, you end up chasing something that isn't a problem..
Don't ask how I know this It took me a while to figure it out.

What had me confused was that you stated a couple of times in your first post, “ by design” What is really happening is that the fluid is taking the path of least resistance

[Stretch]

Gas will flow to the point of least resistance first. The carbs should get fuel only when the fuel in the bowl drops to the point of opening the float needle valve. So, if you close one float valve on each fuel circuit then it should come out through the other carb.

[TwoTired]

Reading thread.  ...wow... just wow...  How can communication be so poor?


Cheers??

[bryanj]

Problem TT is the many varying countries that people come from on here! Its bad enough UK English to US English-----took me months to figure out whar a tree or a wristpin was but bet you wondered about yokes and gudgeon pins!!!

[my name is nobody]

If what I posted is wrong, please correct it. I only meant to simply describe the way fuel flows through the 2 port petcock. Maybe I didn't quite word it right. My reply was meant to add to what was already posted. Sorry if there is any misinformation or if I stepped on anyone's toes.   

[Don R]

 I've seen the top of the petcock covered with rust flakes, I normally rebuild a petcock when I can and clean it out. Do what makes sense, inline filters may be problematic at times. If you have a flow problem that's a good first thing to eliminate.  I had one that I could blow air through into the tank but fuel would not drain out through it, even with the line hanging straight down and open.
 Maybe you need more gas?

[vulture0027@gmail.com]

Is it important to match a specific port of the gas tank to a specific port to the carbs?

[vulture0027@gmail.com]

Also: deltarider- I tilted the tank (at least) 50 degrees.... has still didn’t flow from the “on” position..... didn’t put more gas in yet though.

[Deltarider]

Is it important to match a specific port of the gas tank to a specific port to the carbs?

No.

[Deltarider]

Also: deltarider- I tilted the tank (at least) 50 degrees.... has still didn’t flow from the “on” position..... didn’t put more gas in yet though.

I suggested this, because it helped me out a couple of times when stranded without gas. After the remaining gas in the RH side had travelled into the LH side, I had enough to reach a gas station. Just fill the tank some more.

[PeWe]

Good idea to have a new o-ring available for the petcock bowl. It might leak after you have had it apart after cleaning the mesh filter inside.

[Don R]

 It always surprised me how flat that o ring gets. The ones in my kit are always too fat to allow the threads to start. I bought a few genuine Honda ones to have on hand. The one on top of the petcock also may not reseal and the screw washers will sometimes be an issue. A small cost but a big issue if you don't have them and need them.