Topic: fuel not flowing from carbs 1 & 2 over to 3 & 4

[Somemonkey]

Ok folks, I tried finding an answer in past posts but had no luck. If this question has already been answered, I apologize.

I had the carbs off the bike not long ago to clean them and adjust the float levels. Since then, fuel isn't flowing over to carbs 3 & 4. I have a petcock with two valves. One is the regular fuel valve and the other is the reserve. I have a hose going from either valve to both sides of the carbs. Turns out the reserve valve is connected to the right side of the carbs (3&4). In the past I only had to have the main line running into carbs 1&2 and fuel would get to all bowls. Now I have to have the petcock turned to 'reserve' so fuel flows to both sides of the carbs. There's obviously a blocked hole someplace but I don't know where it's located. Do I have to take the carbs back off the bike to unblock the hole or do you think I can do this without taking the carbs off the bike?

Any help is greatly appreciated.

[Bob Wessner]

I'm a bit confused. When you say, "I have a petcock with two valves" do you mean two outlets? What year/model bike is this? Is this a stock fuel tank and carb set-up?

[Somemonkey]

I'm a bit confused. When you say, "I have a petcock with two valves" do you mean two outlets? What year/model bike is this? Is this a stock fuel tank and carb set-up?

Yes, I mean outlets. It's a 1976 CB550. The fuel tank is actually off a 73 CB500 and the carbs are stock. (as far as I can tell)

[Bob Wessner]

I'm going to assume the petcock/carb set-up is the same as other models with two outlets. The distinction between the main and reserve on the tank is a function of the petcock. Both outlets serve to feed the carbs (one outlet for 1&2 and the other for 3&4) and whether it is on main or reserve depends on the position of the petcock valve. I believe the main setting if fed via a tube that extends up into the tank. When the level of fuel gets below this tube opening, you have to move the petcock valve to 'reserve' to get the fuel to feed through the bottom of the tank, at least that's how it works on my 750. This sounds more like a petcock problem or blockage to me. The only thing that confuses me is your statement;

In the past I only had to have the main line running into carbs 1&2 and fuel would get to all bowls.

[Somemonkey]

I'm going to assume the petcock/carb set-up is the same as other models with two outlets. The distinction between the main and reserve on the tank is a function of the petcock. Both outlets serve to feed the carbs (one outlet for 1&2 and the other for 3&4) and whether it is on main or reserve depends on the position of the petcock valve. I believe the main setting if fed via a tube that extends up into the tank. When the level of fuel gets below this tube opening, you have to move the petcock valve to 'reserve' to get the fuel to feed through the bottom of the tank, at least that's how it works on my 750. This sounds more like a petcock problem or blockage to me. The only thing that confuses me is your statement;

In the past I only had to have the main line running into carbs 1&2 and fuel would get to all bowls.

Maybe i was a bit confusing before. My apoligies.  Let me attempt to clear it up:

Fuel flows from my tank to the left side of the carbs. bowls one and two fill but fuel doesn't make it over to bowls three and four. In the past, before I cleaned and adjusted my carbs, fuel would flow to all bowls from the left side. Now the only way I can get fuel to bowls three and four is to turn my petcock to reserve. The reserve line is attached to the right side of my carbs. With this setup fuel now flows to the right and left side of the carbs. There is something wrong with this though because I should only have to have the main fuel line feeding to the left side of the carbs in order to fill all bowls.

[rlarkin70]

There is something wrong with this though because I should only have to have the main fuel line feeding to the left side of the carbs in order to fill all bowls.

I think this is where you are going wrong. Like Bob said, the reserve/main setting is a function of the petcock itself. Fuel SHOULD be delivered to both outlets in either case. One of them feeds 1&2, the other 3&4. There is no path for fuel to enter the 3&4 carbs through the 1&2 fuel inlet. The T-fitting just goes to the 2 carbs it is directly connected to.

[Somemonkey]

There is something wrong with this though because I should only have to have the main fuel line feeding to the left side of the carbs in order to fill all bowls.

I think this is where you are going wrong. Like Bob said, the reserve/main setting is a function of the petcock itself. Fuel SHOULD be delivered to both outlets in either case. One of them feeds 1&2, the other 3&4. There is no path for fuel to enter the 3&4 carbs through the 1&2 fuel inlet. The T-fitting just goes to the 2 carbs it is directly connected to.

Awesome. Thanks for the help. I was under the impression that fuel somehow flowed from the left side of the carbs all the way over to the right. I actually ordered another petcock the other day because it needed to be replaced anyway. This should solve all my problems. Thanks!

P.S. When I said "in the past fuel would flow from the left to the right side fo the carbs", I was basing that on the fact that fuel would intermittently flow from the petcock to both sides the carbs. I really just assumed the fuel was also able to flow from one side of the carbs to the other via some sort of mysterious fuel opening. Yea, I've got some learnin' to do.   

[Bob Wessner]

You could check your current petcock. Make sure there is enough fuel in there to feed the 'main' setting, that is pretty full, not down to the last gallon or so. Remove the fuel lines from the petcock and hold a container under it. Turn on the petcock. You should get fuel from both outlets. Turn it to reserve, and you should still be fuel from both outlets.

[Somemonkey]

You could check your current petcock. Make sure there is enough fuel in there to feed the 'main' setting, that is pretty full, not down to the last gallon or so. Remove the fuel lines from the petcock and hold a container under it. Turn on the petcock. You should get fuel from both outlets. Turn it to reserve, and you should still be fuel from both outlets.

I'm just going to replace the petcock I currently have. It doesn't shut off all the way and it's not in the best shape anyway. In the long run I'd be better off with a new one rather than trying to fix/rebuild this one.