Does the float bowl have to be super clean?

My motobecane wont run. I tried cleaning out the carb but I cant get the bowl super clean, theres still a white chalk film on the sides and bottom. Ive got spark, fuel flow from the tank, and some doesnt fire my thumb out but does push it out. Any tips.

Re: Does the float bowl have to be super clean?

Thats white stuff's just corrosion.. if you want to take some fine sandpaper to it i guess its ok, but i think it's better to leave it alone. What you do not want is _any_ sort of loose particles in the bowl.

Like yesterday the bike seems a bit sluggish and i developed a idling problem after a short drive. I opened the bowl and there were a few thin tiny black pieces of something in the bowl. The black color makes me think it came from some gasket sealant i used on the float bowl O-ring a while ago. Then again i might have a fuel line that should be replaced..

They were tiny, but large enough to partially block the even smaller idle jet. After a cleaning, the bike was back to normal.

Re: Does the float bowl have to be super clean?

as far as checking your fuel delivery from the carb to the engine, spray some Starter Fluid into the plug hole or the carb's air intake.. Kick it over and if the engine runs for a moment, you do have a carb problem, probably on the order of a blocked passage..

Compressed air is almost mandatory for clearing the passageways of flakes or rust or whatever.

Re: Does the float bowl have to be super clean?

ill try the starter fluid trick. Ive cleaned out the carb with both carb cleaner and compressed air. im just thinking that the float is sticking to the sides and not letting fuel in, or that theres not enough space between the float and the bowl to let fuel in, ie... because of the white chalk stuff.

Re: Does the float bowl have to be super clean?

well thats a different story.. The float itself should be completely free to move. If you have such serious corrosion that the float actually touches it..... (???) ..

forget that.. you would need about 1/8 inch of corrosion on the walls of the bowl.. Thats not likely to happen in a hundred years.

Hopefully the carb is correctly assembled. If so the float will be free to move.

Temporarily connect the carb to the tank's fuel line while it's off the bike and turn on the fuel petcock. Hold the carb level. Wait a couple minutes and turn it off. No leaks? OK. Carefully remove the bowl and see if its full of fuel. If so, your float and needle are working properly.

do the Starter Fluid thing..

Re: Does the float bowl have to be super clean?

Thats a good trick too! Ill give it a shot.

when trying to get it started it chunks chuncks chunks but never catches into a run. This is why I think it is a fuel problem....i feel the compression and Ive tested for spark. the decompresser is a bit of a pain I cant seem to get it on the right level.....some times too much decompress....sometimes too little.

The choke is a bit confusing as well in these doesnt really make sence how its set that little brass thing chokes it seems weird to me.


Re: Does the float bowl have to be super clean?

Gregory Mcintire /

There are a number of kitchen cleaning products that will gett rid of that white stuff in your bowl. I have used one called "Lime Away". There are others also which are advertised to get rid of scale on kitchen and bathroom fixtures that will work very well.

Re: Does the float bowl have to be super clean?

Lime away and stuff like that will work. Carbs are made of a 'pot metal' alloy, primarily zinc, and mild acids will dislodge and dissolve the various oxides..

(it may also have an effect on the brass jets but i'm not sure.. I do know that those acids attack both the oxides and the base metal, but they attack oxides much more quickly)

My concern would be that once you loosen that corrosion up, whatever you don't thoroughly take care of, like up in the passages, may start flaking off.

Sandpaper or steel wool is likely to leave bits of sand or steel imbedded in the soft metal.

The fact that you need acids or abrasives to take that corrosion off shows that it's stuck on there real good and isn't going anywhere. I wouldn't mess with it unless i had good reason.

Re: Does the float bowl have to be super clean?


I fixed it!!!!!! I took a dremil tool and polished up the inside of the bowl. Now she works like a charm....well a charm that wont idle.

It runs great, starts well, but when Im at a stop it dies.

Ive tried adjusting the idle screw but it doesnt help. Ive also done a plug chop and alls well in there. Ive got allot of blue smoke comming out of the exaust pipe.

Any tips?

Re: Does the float bowl have to be super clean?

here's how i do it .. if you have both an idle speed screw and an idle air screw this should work.

Take the bike for a 3 or 4 mile ride to warm it up.

Come to a stop (engine died?) and turn the speed screw in far enough to keep the engine running (kick it over again). The speed screw is the one on the carb that that pushes on the throttle linkage open.

Now slowly turn the Air screw in and out until you hear the engine speed up. This means the idle air/fuel mixture is now better.

Now back out the speed screw and slow the engine 'till it threatens to die. Again, turn the Air screw in or out till it speeds up. Then slow the motor down again with the speed screw.

Test ride and readjust if needed.

Re: Does the float bowl have to be super clean?

perhaps you put the bowl on backwards-

some carbs the bowl can go on many ways, but only one way will allow the bowl to move

turn the bolw around.

When you have the carb in ur hand- shake it gently and you should feel/ hear the float move


Re: Does the float bowl have to be super clean?

Which one is the air screw. I do see a silver screw on the bottom of the carb which leads to the main jet that it?

Re: Does the float bowl have to be super clean?

(Now I'm talking generic carburetor construction.. )

The passageway for idle fuel is somewhere above the float bowl. This fuel is mixed with air that enters a hole somewhere in the air-horn of the carb. So, both the little idle fuel jet and the air pilot screw will be somewhere higher than the float bowl. (You probably will never see the idle _jet_ unless you disassemble the carb and maybe pull a plug.)

The air screw is usually mounted where it's easy to get to, perhaps right next to the speed screw.. It will have a spring on it which keeps the screw from moving after adjustment. The speed screw also has a spring on it.


Damn.. forget all that.. here's a manual for a motobecane

I dont see any air-adjustment on page 20.. only idle speed. My guess is that its set at the factory. If the carb is clean and idle speed is set, there is no need for idle fuel/air adjustement.

I may be wrong or have the wrong manual.

Now the Clutch is broken!!!Help

Well the carb is all clean and working well. But....the clutch is acting up. It is getting jammed and killing the ped when at idle.

I replaced the clutch parts withs another motobecanes parts and its still happining. I really dont understand how the clutch works and why its jamming.

The pads on both the clutch parts are really worns down at a weird angle(ie.. the pads on the "L" things with the springs)

Is there any way the moped can run without a clutch...seems like a silly question but hey, there must be a way around it, even if it means i cant use it as a peddel bike.....

Re: Now the Clutch is broken!!!Help

I think you are talking about the two start-clutch arms. My PA50 has the two L-shaped arms like that. These are engaged when you pedal fast to start the engine. They make the crankshaft move and that causes compression and spark and the engine starts.

i'm really into hacking hardware.. in fact it's my favorite thing. But if I had clutch pads worn at a weird angle and that clutch is somehow causing the engine to die, i wouldn't even ride it unless it was an emergency.

As far as what will happen if they arent even there, i dunno for sure.. i guess you can disconnect them and start the bike by pushing it if you can push fast enough to engage the driving clutch.

But why are the pads worn like that? Is the clutch housing mounted wrong or loose? Take a close look. The cure might be real easy to figure out. Ignoring a problem with these symptoms could be really bad for that engine.

Re: Now the Clutch is broken!!!Help

Yeah those are the clutch arms. And the outside mounting/spin case is a little loose ie it tends to wiggle a little. But iI think the reason is the peddle disk is loose as well so the whole tends to wiggle. Could that be jamming the clutch?

Re: Now the Clutch is broken!!!Help

sure the wobble could jam the clutch and kill the idling engine. i have a bike with 5,000 miles on it and those clutch shoes look brand new. Your's are getting eaten up.

Why is anything in that area loose? Is it something that can't be tightened.. did something get bent?

Re: Now the Clutch is broken!!!Help

I just bought the thing last who knows what happened to it for the past 30 odd years. I havent tried tighting the peddle disk yet. I was so concerned with the carb I didnt notice it untill I knew for sure the carb wasnt the problem.

Should the clutch be gressed up in any area?

Re: Now the Clutch is broken!!!Help

if you were reassembling a clutch they might recommend a touch of grease on pivot points or places where metal rubs against metal, but its best to keep grease far away from dry clutches or brakes.

hey.. you fix one thing and you notice something else that needs fixing? it must be a moped.

Do you think I could sand down the clutch arms?

I have two sets of this engine...which means two clutch's. So I was wondering if I should sand down the pad ends on the arms inside one of the least so they arnt at weird angles anymore. ie if I screw one big deal ive got another.

the arms are called weights I think. Anyways just running some ideas off you before I do anything rash.

Re: Do you think I could sand down the clutch arms

If there's enough material left, and you fixed whatever the reason for them wearing at an angle was, it's ok to sand them and square them up.. But someday, maybe soon, you could have metal-to-metal contact. That is a bad thing that wont be cured by sanding something down.

A couple things to consider..

There may be a mechanical limit to the travel of the arms which prevents metal/metal contact when pads wear to a certain thinness..

In any case, if i got this right, the thinner the pads, the further the springs have to stretch and the faster you have to pedal to get the pads out far enough to contact the drum. And they might contact the drum but not have enough force to avoid slipping..

Re: Do you think I could sand down the clutch arms

Hmmmmmm........didnt think of that! back to the drawing board, or back to the root of the problem. It must be the wiggle in the peddle disk thats causing it...or the back peice of the clutch wheel must be warped. Do you think it will be hard to switch those peices with the spares I have.

Re: Do you think I could sand down the clutch arms

Everything is hard until you do it and learn.

i have a spare parts bike with a bent pedal shaft. It has no connection to the clutch(es) The end of that shaft will have to be cut off to get the shaft out, unless i want to risk bending the frame tube that it runs through.

So, it all depends.. There is no substitute for getting down there with a manual and some tools and figuring out what needs to be done and doing it.

I think I know the real problem

Upon reflection I think the real problem is that the Moped idle is way too high which is engaging the clutch when the moped is stopped..but running.

Is there any way to slow down the idle, besides turning the idle screw out.

Could it be that the exaust is slightly clogged and making the engine work too hard?

Funny, such a small simple engine but so many reasons for poor performance.

Re: I think I know the real problem

Is there an idle-air screw to adjust the idle-fuel/air mix on that carb?

If so you should be able to use both the air screw and the idle speed screw to slow it down.

What you would do is back off the idle speed screw until the engine is about to die and then adjust the air screw 'till the engine speeds up a little. ( It will speed up when the air-fuel ratio gets better. )

Then slow it down with the speed screw and do the same thing again with the air screw.

Piston-ported intake 2-strokes do not idle well. At low RPMs there is enough time for the mixture already in the crankcase to go backwards into the carb and load up with even more fuel. This causes misfires at idle, commonly knows as 4-stroking.

You may also have air/vacuum leaks that are preventing a smooth slow idle. Check this by spraying Starter Fluid (auto parts store) around the carb joints. If you hear the engine speed up you can be sure some of that Starter Fluid (highly flamable ether) is getting sucked in there.. and you have a leaky gasket someplace.

Vacuum leaks will make the bike run kinda crappy at all speeds. To me it feels like the engine never really warmed up, has some trouble reaching top speed or climbing hills, and it tends to die when it comes to a stop.

Re: I think I know the real problem

wouldnt the air screw have a spring attached? On the motobecane carb there is only one screw with a spring and that is the idle crew. I believe the air mix was factory set.

Do you think it may be the muffler being clogged?

Re: I think I know the real problem

yeah.. an air screw, or any adjusting screw for that matter, will have a spring on it to keep tension.

ok.. clogged muffler? I guess that could make you set the idle rpm high.. Anything that is abnormal could do the same thing. The thing aint gonna idle right unless the engine and carb and everyhing else is clean and tight.

But since this new thread started off with the clutch, i suspect the opposite of what you suspect. Instead of a high idle causing the clutch to engage, the clutch is dragging, and so forcing you to have to set a high idle rpm.

Re: I think I know the real problem

explain "clutch dragging"

Re: I think I know the real problem

When a clutch pad is touching it's friction drum _before it should touch it_ it's dragging.

Same as a dragging brake.. that brake is always in contact with the brake drum.

Re: I think I know the real problem

I figgured thats what you meant but i wanted to be sure.

hey joe thanks allot for all the help youve givin me a 28 message length chain is quite a lot time to spend.

I might be able to tinker with it tonight and will let you know how it goes.

Thanks Again!

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