Topic: Carburetor drain hose weeps

[majorzozo]

Hi all,

Recently I have noticed my carburetor drain hoses weeping after about 20-mile rides.  78-750F with about 750 miles since restoration. They weep with maybe a drip or two within 5 minutes then completely stop. I shut off the fuel always about 1/4 mile from home.  Is this considered normal or is this a sign of the rubber deteriorating on the float needle valves?  Thanks in advance.   

[denward17]

Could be the float needle valves, or the level set too high.

Could be fine trash in the line, does it do it every ride?

[majorzozo]

Yes, it does it every time but stops after about 5 minutes.  Thanks, Denward.

[willbird]

Yea IMHO that means that the fuel level is too high. I played with float levels a bit and got my bike to a places where fuel would come from some overflows when bike was on sidestand. It could be that your needles leak a little or you may have your float levels set too high maybe IMHO.

Bill

[majorzozo]

I was hoping you would say "Yah, they all do it".  Hahahahaha.  Thank you both for the replies.  Time to get some valves on order.  Thanks again.

[willbird]

I was hoping you would say "Yah, they all do it".  Hahahahaha.  Thank you both for the replies.  Time to get some valves on order.  Thanks again.

What does your sediment bowl look like ?? Just a tiny amount of trash really harshes their mellow :-). Not sure if you have done it yet but you can unhook your fuel lines and install temporary ones to a container then flip the petcock to reserve which should drain any debris out of the bottom of the tank, and what will not go through the screen ends up in the sediment bowl. No intent to drain the tank here just run anything laying in the bottom out, 12 ou ces would be plenty enough I bet.

Back in the 70's having to flip a Honda to reserve could really bring on some %^$# due to more water present in the fuel and fuel tanks. All kinds of junk laid in wait for the day you hit reserve. Maybe guys who hit reserve every tank were better off.

When I put a new petcock on my K2 I discovered that as long as my dad had that tank on it and as long as I have had there was never any standpipe and thus no reserve, plus it sucked all the junk out of the bottom of the tank every time he and I rode it.

Bill

[BenelliSEI]

Your symptoms suggest the float levels are set too high and after you stop, the fuel in the bowls gets hot, level rises just enough to overflow.

However…. If your’re shutting off the flow well in advance, this should not happen. Any chance your petcock is not holding? Sure you have it off and not on reserve?

[Ozzybud]

I was hoping you would say "Yah, they all do it".  Hahahahaha.  Thank you both for the replies.  Time to get some valves on order.  Thanks again.

What does your sediment bowl look like ?? Just a tiny amount of trash really harshes their mellow :-). Not sure if you have done it yet but you can unhook your fuel lines and install temporary ones to a container then flip the petcock to reserve which should drain any debris out of the bottom of the tank, and what will not go through the screen ends up in the sediment bowl. No intent to drain the tank here just run anything laying in the bottom out, 12 ou ces would be plenty enough I bet.

Back in the 70's having to flip a Honda to reserve could really bring on some %^$# due to more water present in the fuel and fuel tanks. All kinds of junk laid in wait for the day you hit reserve. Maybe guys who hit reserve every tank were better off.

When I put a new petcock on my K2 I discovered that as long as my dad had that tank on it and as long as I have had there was never any standpipe and thus no reserve, plus it sucked all the junk out of the bottom of the tank every time he and I rode it.

Bill

This bike does not have a sediment bowl.
It has a full sock filter inside the tank that filters fuel in the on and reserve position.

Drain your carburetor bowls one at a time and look for debris. I had a problem a few years ago with my F1 where the hose i was using for replacement was some knockoff  Chinese stuff and was disintegrating from the inside. Leaky carburetors was my first symptom.  There was black debris in all the bowls
A tiny bit in the float valves caused havoc.
I did not have to remove the carburetors to remedy. I just replace the Fuel lines with OEM from Honda and flushed it out. Get fresh gas in the system and tap on the carbs a few times to clear any remaining debris out and drain the bowls a second time hoping nothing got into your idle circuit.

[majorzozo]

Thanks everybody for the suggestions.  I will check and try all before pulling the rack.  I can assure the floats were set at 14.5 MM and also the bike has never ran better.   

[newday777]

750 miles since the rebuild, that isn't riding it very much(Motorcycle Abuse!! ), so you definitely need to do some inspection and cleaning. What are you using for fuel in the tank? I know that non ethanol gas is very hard to find there in California.....

Have you taken a Qtip soaked in carb cleaner to the brass float valves yet? That sometimes makes the difference in the weeping to stop. Pull the valves out and spin the Qtip into the brass funnel to clean anything stuck to the brass body so the valve tips can seal better and inspect the valve tips for any sign of wear.
I've had the weeping after rides, yes even after shutting off the petcock a 1/4 mile from the garage and running the engine until it quits on my K5, sometimes the next morning there has been a small spot on the floor. It is frustrating at times especially after having closely checking the float heights.

A little bit of surface rust in the tank can let little specks of rust in the float valves so they don't completely close off the flow. Use a bright flashlight to look in the tank opening, and use a bore scope to inspect the inside of all the tank. You will see some discoloration in the float bowls if you have any rust in the tank. The tank needs to be derusted if there is Any surface rust, or more, in the tank.
I highly recommend electrolysis cleaning for 4-5 days, rinse with diesel fuel not water. Followed up with full tank of Evaporust(5 gallons) for a couple more days, then rinse out with 2-3 quarts of clean diesel fuel 3-4 times to clean out the Evaporust fully. Then immediately swish 6 oz of 2 stoke oil around the inside of the tank to coat all surfaces to prevent surface rust from starting again and dump out the excess oil into a container. A little 2 stoke oil in the gas doesn't hurt, even helps lube the carbs. You can add a couple oz 2 stroke oil to a full take of gas as rust preventative maintenance.
Dump the deisel rinse into a clean 5 gallon bucket to allow the Evaporust to settle to the bottom and you can later reuse the diesel fuel in a week for the next cleaning of a tank by leaving the dark Evaporust in the bottom of the bucket while slowly pouring out the diesel fuel into a clean storage container.

[newday777]

A just a little helpful FYI so it will last longer.
If you are going to leave the bike in storage more than 4 months, especially if you use any ethanol fuel, I highly recommend draining out the tank and doing the diesel fuel rinse, then coat the tank again with 2 stroke oil for the storage time. I do it every winter here in NH.
Less than 4 months, be sure the tank is always kept full to prevent moisture in the tank.
Ride your bike every week at least 50 miles at a time to get all moisture burned out of the motor and exhaust and well exercised. Just starting it without riding it is worse than not running it.

[BenelliSEI]

Thanks everybody for the suggestions.  I will check and try all before pulling the rack.  I can assure the floats were set at 14.5 MM and also the bike has never ran better.   

If the “bike has never run better” why not just flip the petcock a little earlier? If that doesn’t make any difference, I’d check that shut off first……

[majorzozo]

Thanks for all the tips fellas.  Unfortunately, health has been limiting my rides.  Tank is rust free and I will double check the fuel shut-off.  Non ethanol fuel is almost impossible to find so that is what I use. I will also drain each bowl individually to look for sediment.  If all that checks out I'll replace the needle valves and also the Orings on the drain screws.  Thanks everyone.     

[newday777]

I hope you are feeling better soon so you can get out on it before the real hot begins there.

[newday777]

#2 float valves depending on your vin numbers

https://www.southsoundhonda.com/--xpartsstream#/Honda_Powersports/CB750FA_(78)_750_SUPER_SPORT%2c_JPN%2c_VIN%23_CB750F-2200001/CARBURETOR_COMPONENTS/e6527cd1-1769-44c7-8c35-4025df7c537a/27a38075-6e0b-4d1b-ac99-5a10bb4ffd7e/y