Carb problems, please help!

Nicolas Anbeek /

Hi everybody, and thanks for reading this. Please bear with me as I'm new to engines and learning as I go, but still quite ignorant.

I have a 1974 Batavus Bronco (dutch). The other day, I think while adding oil to the tank I think I got some shit in there somehow. The moped stopped running, with symptoms of fuel system problems - i.e. it would run for twenty feet, then stall. Then I'd wait, and it would run again a bit, and stall.

So... I took the carburetor off, and cleaned it all out. I sprayed every orifice with carb cleaner and even soaked it over night. Then I rinsed everything out with gasoline, and put it all back together.

Now, the problem seems to be a BIT better, but it's still messed up somehow. I can keep it running if I play with the gas and choke, but it keeps trying to die on me. It also lurches and stuff.... revving the gas-grip doesn't let me GO like before, just moves it a bit, then slows down, etc. However, if I run the bike on the center-stand, it goes no problem... I can spin the wheel indefinitely without it stalling.

(Sorry if I suck at describing this).

Can anybody provide ANY clues as to what my problem is? I'm quite sure I put the carburetor back together properly, yet I'm sure it's a carb problem. The ignition is fine, there is a good spark (it starts with two different spark plugs), etc.

Any advice?

Thanks in advance!

Nick

Re: Carb problems, please help!

SteelToad /

It sounds as though the fuel may not be getting out of the tank. Try running a

fuel line from another source (small bottle or such) and see if that works.

(Just guessing here)

Re: Carb problems, please help!

Ron Brown /

Nick,

You say you were adding oil to the tank. Is this the gas tank, as in premix, or the oil tank.

If you were adding oil to the fuel tank, this is wrong. You should allways mix the fuel in a separate container and shake it up.

Disconnect the fuel line at the carb and make sure fuel flows freely. If it does, drain the tank and try new fuel mix.

If not, remove the petcock and clean it.

Ron

Re: Carb problems, please help!

Nicolas Anbeek /

So it's not ok to add the oil directly to the tank? Ok, well I've learned something!

Anyway, I know the fuel flows freely because I have disconnected the fuel line at the carb and let it flow freely into a little bucket.... so that's not the problem. It also seems clean. Should I still drain the tank and start over?

Re: Carb problems, please help!

Nicolas Anbeek /

By the way, how do I remove the petcock? Is that where I turn the fuel from on/off/reserve?

Thanks.

Re: Carb problems, please help!

Ron Brown /

Nicholas,

Yes on the petcock but if it works, don't mess with it.

Yes on draining the fuel and using fresh pre mix.

Don't overdo the oil.

Ron

Re: Carb problems, please help!

I had that problem with my Puch. Turns out it wasnt a fuel problem but an exhaust problem. If your exhaust port is clogged, it will not let all the exhaust out and your mixture will not completely burn. I would recommend cleaning out the exhaust very well.

You'll be amazed at how much faster your bike is if this is the problem.

--(another)Nick

Re: Carb problems, please help!

Nicolas Anbeek /

Yes, I thought about the exhaust, but that wasn't the problem. I took the whole thing off and it made no difference.

So...

I guess the only thing to do right now is drain the fuel tank and start with a fresh mix and hope for the best. But if the fuel is flowing freely and seems clean, is this likely to be the problem?

Re: Carb problems, please help!

How do you clean out the exhaust? Thanks

Re: Carb problems, please help!

Brandon Edge /

Ron,

> If you were adding oil to the fuel tank, this is wrong. You

> should allways mix the fuel in a separate container and shake

> it up.

Why is that wrong?

Brandon Edge

Re: Carb problems, please help!

Simplest way is to take it apart and scrape it with a long screwdriver. If you have a torch or are willing to soak it in gas and light it, that usually works better. Then tap it gently to knock the carbon out.

daveb

Re: Carb problems, please help!

Ron Brown /

Brandon,

If you can guarantee the quantities of gas and oil you add, you remember to close the petcock first and you can pick up your ped and shake it well, no problem.

In practice, ped tanks are so small, that if you try to mix in the tank, you wind up mixing odd quantities which makes it easy to screw up the ratio. Mixing exact amounts in a gas can avoids this problem and you can top off your ped's tank any time even if you are mathematically impaired.

Ron

Re: Carb problems, please help!

most likely its bad gas. my moby is very pickiy about the gas/oil mix. maybe you put too much or too litle oil in. or maybe thats not it at all, but its worth a shot

Re: Carb problems, please help!

Nicolas Anbeek /

Ron,

Regarding adding oil to the fuel tank after adding gas... What I do, is go to the gas station and add an exact, measurable amount of gas, for example 2 litres. Then I know that I need 20ml oil/litre of gas (1:50) so I add exactly 2 X 20ml (40ml) of oil (measured with a measuring spoon I carry around). Then I stir it around a bit with a clean plastic dip-stick which I have. This seems to work quite well. Unfortunately, I think I got some crap in there in the process so I have to re-think my method.

I believe that I have solved the problem of crap in the fuel system, however - because I cleaned every little orifice and hole and nothing's clogged. Here's my new theory... it seems like the bike is starved for gas... i.e. the fuel/air ratio is too lean. If I ride around with the choke pulled halfway, it seems to run fine, or at least much better - it doesn't stall out or anything. SO... when re-assembling my carburetor, I think I messed up the choke cable somehow... does anybody know if there's a way to adjust the choke... so that it's a bit tighter and doesn't let so much air in all the time...? I might have to take the carb apart again and check that out ..... does this make sense? Like I said, the bike will start and run almost perfectly if I hold the choke down.

Thanks again!

Nick

Re: Carb problems, please help!

Are you running an air filter?

(because you should be... it richens up the fuel/air mixture.. which sounds like your problem)

And did you use compressed air to blow out the small orifices in the carb?... (you HAVE to do that)

Re: Carb problems, please help!

Ron Brown /

Nicholas,

I am assuming that before your fatefull trip to the gas station, your ped ran just fine.

You know you have good fuel flow and provided you assembled it correctly, you know you have a clean carburetor.

On the assumption that the only change you have not yet reversed, is the new tank of gas. Drain it out and replace it with fresh mix. This may not be the problem, but at least you will have eliminated the possibility.

AFTER you have done this, if you still have a problem, partially choking the carburetor is not a solution. If you have to do this, you either have too little fuel (partially plugged main jet) or too much air, see Fred's post and check the fit of the carb to the manifold for air leaks.

Do not loose sight of the fact that the ped used to run ok, so you do not have to modify anything to make it run, simply get it back to the way it was when it ran .

Ron

Re: Carb problems, please help!

Nicolas Anbeek /

Hi Ron, thanks for the info.

Based on everything I've read, I'm convinced that I have some sort of an air leak - I changed the fuel and it made no difference. And if it runs ok by manipulating the choke, that must mean my fuel/air mixture is too lean, like you say. SO... what the heck's the problem? I've put the carb back on exactly how it was and everything seems nice and tight like before. The only thing I'm worried about is that there was a sort of ripping "seal?" "gasket?" -not sure of the exact word. It goes between the carb and the manifold where the carb attaches to the bike - it's a small piece of material, almost like cardboard, that was ripping - however, I set it in there exactly how it was and it seemed ok. Could this be the problem, a TINY amount of air getting in there? Seems unlikely, but who knows?

But shouldn't a bike run fine without an air filter (I know it's a bad idea, but in theory it should run, right?).

Hmmmm.. I don't know, I'm stumped. I wish I never took the bloody thing apart!

Nick

Re: Carb problems, please help!

Ron Brown /

Nick,

Got to the auto parts store and buy some gasket material that looks about the same and says it is good for manifold gaskets. Carefully cut a new one and install it. Do not overtighten the bolts, this will distort the flange. Check it with a straight edge and make sure it is ok.

Most peds will run without an air cleaner but some rely on the restriction of the air cleaner to enrich the mixture. Your best bet is to run the configuration that worked before the problem.

Ron

Re: Carb problems, please help!

Nicolas Anbeek /

Thank you Ron for the fantastic advice... like I said, I'm learning as I'm going so I really appreciate your help - and of course, everybody elses.

I will try this within the next couple of days and let you know if it works... it's a great idea!

Nick

Re: Carb problems, please help!

Nicolas Anbeek /

THANK YOU EVERYBODY! My moped is now running, thanks to everybody's help. Cheers!

This place is fantastic!

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