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2004 Honda: idles..rich when throttle is opened..exhaust..air filter

Customer Question

2004 Honda Ruckus starts and idles but sputters rich when throttle is opened. Black puffy exhaust. Carb has been dis assembled and cleaned, new spark plug installed, cleaned air filter, stock jets. Runs better to good at half throttle. Not sure what to check next.

Mike
Submitted: 2 years ago.
Category: Motorcycle
Expert:  .... replied 2 years ago.

Brian :

Good day and welcome to Just Answer. My name is XXXXX XXXXX I'd be happy to help you with your problem today.

Brian :

Black puffy exhaust is a rich condition either due to over fueling or not breathing.

Brian :

I think you need to look into the carb set up, a stuck choke or a valve adjustment.

Brian :

If not all of them

Customer:

I know this. What part of carb setup? This does not have a choke. It has enrichment needle valve. How should it be adjusted? Valve adjustment has been checked and is oK.

Brian :

The fuel mixture & float adjustment. That has an auto choke on it, & they get stuck.

Customer:

I am sure choke is not stuck. Scooter starts immediately and idles well even after warm. This suggests the start enrichment system is closing properly. The only fuel mixture is for idle and is a "D" screw near the front of the carb which I cannot turn. Would this adjustment have any effect on high speed operation? Float bowl is not overflowing and seemed to close properly when I reassembled the carb. Is float level critical?

Brian :

Yes, if the float level is too high you have rich condition.

Brian :

There is no indication thus far that the choke is not stuck and I'm not sure why you are trying to convince me otherwise when your symptoms contradict your thinking.

Brian :

Idle adjustment is not fuel mixture & all carbs since the 80's have had to have mixture screws on them & in fact your carb can not be cleaned without removing it.

Brian :

Yes, fuel mixture adjustment can effect all or certain rpm ranges depending on your fuel mixture needs.

Brian :

Unfortunately because I don't have the carb in front of me I can only suggest to you what I suspect as an issue based on your symptoms

Brian :

Since you know the valves are good I think the issue is the mixture or float level, with the "by-starter" deal being last on the list.. definitely over fueling

Customer:

Are you familiar with this exact carb? It does not have the traditional low speed, high speed mixture screws common on other carbs. There is one screw with a "D" head which is not meant to be adjusted according to what I read and it is for idle, not high speed. You need a special screwdriver for it which I don't have. It does not have a "choke"; instead it has a needle valve which is open cold and electrically closes as the engine warms up. The only thing that makes sense to me is the float level. Any other ideas? Could the throttle position indicator be involved?

Brian :

There are no carbs that I'm aware of with two mixture screws. Most have 2 jets but all only have 1 mixture screw.

Brian :

An idle adjustment only adjusts mixture on a 2 stroke carb, you do not have that. & yes, you set the idle & only adjust as necessary.

Brian :

It does have a choke, it an auto choke called a "by-starter valve" by honda, otherwise know as an electric or auto choke, if you need to refer to it as a needle valve that is fine, but be clear, it is an auto choke.

Brian :

You have to understand that fuel mixture adjustments & idle screws are not the same & you are dealing with 4 stroke carb not 2 stroke small engine carb. They are very different & are tuned differently.

Customer:

Do you know where I can get a driver for this "D" shaped mixture screw? Or is there some clever way to use existing tools to turn it?

Brian :

You have a 2 jet carb with a fuel mixture screw right on the side of the carb. As per epa regs the mixture screws are capped from the factory, but I would think on an 04 the carb would have been serviced several times & the cap removed.

Brian :

That is just a thumb screw as far I know, maybe I'm not clear on what you are referring to & since that is an idle adjustment only, is not your issue.

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Expert:  .... replied 2 years ago.
I'm sitting here looking at the exploded view of your carb, I'm not sure what we didn't get together on?..
Customer: replied 2 years ago.
I agree that the idle is not the problem but it is not a thumb screw. It is a recessed screw with a brass end with a "D" shape. I was finally able to remove it and cut a slot in it so I could adjust it. As expected, adjustments make a small difference in idle but no effect on high speed.

I checked the float and as far as I can tell there is no adjustment. It is all plastic except the pointed valve itself which looked OK. On reconnecting, I checked the fuel pump. I barely moves any gas at all and would not fill the bowl. I removed the gas tank and gravity fed the carb and the bowl filled and turned off. The scooter than started and idled but stuttered when the throttle was opened and would only stay running at half throttle. I know this seems weird but that is what is happening. Can you tell me how much gas the pump should deliver?

I am thinking the next step is new jets and maybe a new fuel pump.

Other ideas?
Expert:  .... replied 2 years ago.
You would only need new jets if they are not clear, which is easy to check visually.

Removing & slotting that screw was not ever to accomplish any positive results.

Clogged jets would not cause an over fueling condition, & without a adjustable float tang only the float needle itself will leak & over fuel.

The fuel pump is only there to fill the carb it is not a pressurized system but will over fuel if the float needle tip is shot.

You have an over fueling condition, I'm clear on that. Because you are there you'll need to determine why that is. I personally think the valve clearances are the main issue but that is just what I see in the shop. The other is stuck by-starter valves & bad float needles.
Customer: replied 2 years ago.
The jets look clear and have been overnight in carb cleaner and blown out. However, this scooter sits for six months at a time and had gas go bad in the past. Is there a chance that even though you can see through the jets, they are still microscopicly restricted?

Again, the pump does not put out much, only a dribble. It would probably take several minutes to fill the bowl. Is this normal?

I will check the valve clearances again.
Expert:  .... replied 2 years ago.
The main jet is far too big to clog. The pilot jet should be fine after an overnight soak. I normally use lacquer thinner on brass jets to avoid any question on that issue.

That float bowl in not very large so it does not require much fuel, that is like a 3 psi system.

You should also keep in mind that the same fuel that gums up the carb gums up the pump & causes the same issue there.

Which would be opposite of you issue & why I think you are going in the wrong direction.

If the pump were an issue you would be over fueling.

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