Petcocks and Flowing Fuel

[DJM]

I had a similar problem with my CL77 which isn't fitted with in line filters.

Not a problem when leaving the bike standing but will show similar symptoms if the fuel level is allowed to drop enough to need Reserve,

Unless switched over very quickly the bike would drop onto one cylinder and stay that way.
Initially I was taking off the float bowl or fuel line to get the gas flowing again, later I hit on an easier solution. Take off the filler cap and BLOW into the tank. If your lungs are in decent condition the pressure in the tank will be enough to get the gas flowing again.

I've had CBs for around fifty years and never come across this before but my brother in law who had a CB77 back in the 1960s said he had to do the same thing if he let the fuel level drop onto Reserve. My CL problem never really went away I just make sure to refill the tank after around 100 to110 miles, that way I never need to use the reserve position.

As there is a filter in the fuel tap and two more on the carb unions there isn't really a need for the in line filters, they look awful anyway.

[LOUD MOUSE]

Ya aware tha tHONDA discontinued the ( two more on the carb unions ) in the 1967 production carbs?. .........lm

I had a similar problem with my CL77 which isn't fitted with in line filters.

Not a problem when leaving the bike standing but will show similar symptoms if the fuel level is allowed to drop enough to need Reserve,

Unless switched over very quickly the bike would drop onto one cylinder and stay that way.
Initially I was taking off the float bowl or fuel line to get the gas flowing again, later I hit on an easier solution. Take off the filler cap and BLOW into the tank. If your lungs are in decent condition the pressure in the tank will be enough to get the gas flowing again.

I've had CBs for around fifty years and never come across this before but my brother in law who had a CB77 back in the 1960s said he had to do the same thing if he let the fuel level drop onto Reserve. My CL problem never really went away I just make sure to refill the tank after around 100 to110 miles, that way I never need to use the reserve position.

As there is a filter in the fuel tap and two more on the carb unions there isn't really a need for the in line filters, they look awful anyway.

[DJM]

To clarify, are you saying that the filter gauze inside the carburettor fuel union bolt was discontinued on the late bikes? I didn't know that as I've never worked on a bike that new in fact not many, if any, of the last series CB77s made it here.
Honda UK were still selling off 'old stock' pretty well to the end, we certainly never had the chrome fenders and candy paint colours here, never saw the folding footrests and didn't even get that many of the bikes with the late type alloy forks.

[LOUD MOUSE]

Yep.
That's what HONDA discontinued. .................lm

To clarify, are you saying that the filter gauze inside the carburettor fuel union bolt was discontinued on the late bikes? I didn't know that as I've never worked on a bike that new in fact not many, if any, of the last series CB77s made it here.
Honda UK were still selling off 'old stock' pretty well to the end, we certainly never had the chrome fenders and candy paint colours here, never saw the folding footrests and didn't even get that many of the bikes with the late type alloy forks.

[mark acker]

I have a 1967 Honda 305 scrambler CL77. I can't get the fuel to flow evenly from the petcock to the fuel lines to the carbs. One flows free, the other line won't flow at all. I can block the flowing line and other line starts to flow, but slowly and weakly. When I unblock the other line, that one stops flowing.

The petcock is cleaned, the ports inside are clear. Gas is getting to the petcock, but the trouble starts there. The petcock packing gasket behind the lever has been changed too.

Any help out there?

I'm not sure I'm understanding. Are you doing this flow testing with the two hoses still attached to the petcock and just disconnected from the carburetors or are you pulling the hoses off of the petcock and then comparing flow from the petcock's two metal hose fittings?

I have done it both ways. Usually I take the hoses off the carbs and leave them attached to the petcock hose fittings. It seems I might have a vacuum problem, my gas cap has some crud inside. Got most of it out yesterday, but still have flow problems. Got the flow started by dropping the carb bowels a little. The bike starts but runs rough, wont idle and won't keep running. It seems to be starving.

[mark acker]

Ya aware tha tHONDA discontinued the ( two more on the carb unions ) in the 1967 production carbs?. .........lm

I had a similar problem with my CL77 which isn't fitted with in line filters.

Not a problem when leaving the bike standing but will show similar symptoms if the fuel level is allowed to drop enough to need Reserve,

Unless switched over very quickly the bike would drop onto one cylinder and stay that way.
Initially I was taking off the float bowl or fuel line to get the gas flowing again, later I hit on an easier solution. Take off the filler cap and BLOW into the tank. If your lungs are in decent condition the pressure in the tank will be enough to get the gas flowing again.

I've had CBs for around fifty years and never come across this before but my brother in law who had a CB77 back in the 1960s said he had to do the same thing if he let the fuel level drop onto Reserve. My CL problem never really went away I just make sure to refill the tank after around 100 to110 miles, that way I never need to use the reserve position.

As there is a filter in the fuel tap and two more on the carb unions there isn't really a need for the in line filters, they look awful anyway.

[mark acker]

Not sure I am getting the hang of this forum, can't tell if my replies are getting out or not. To Seadog, I have tired both methods, usually disconnecting the hoses from the carbs and leaving them attached to the petcock fittings. Got better flow yesterday after cleaning out the vent hole in the gas cap, but still get uneven flows, bike wont keep running. It appears to be starving out.

Along those lines, do you or anyone else know what the two small lines coming off the back of the cylinders, right next to where the carbs are attached are for? They come together in a "Y" and it seems that tube goes into one of the air filters? What impact does this have on carburation?