cant let go of the choke (mobylette)

ok i wasnt able to start my mobylette, untill today. before i had thought that it was the compression or god knows what else, but i tinkered with it a bit annd was able to get it to go. the only problem is that when i finally get it to turn over i have to hold the choke and pull the throttle a little bit and if i let go of the choke i die out.

i am still having a problem also with the throttle cable getting stuck open and not closing which is scary as all hell...

so i i think if i can fix these issues i will be able to ride my hot new mamma around and scare all the small children, that is untill i get my exhaust hooked up haha

am i wrong or is it bad to have to pedal a few times to get it to start, is that a timing issue?

Re: cant let go of the choke (mobylette)

in regards to the choke thing, it sounds like you need to cut some air intake to get the correct air:fuel mixture. This indicates that not enough fuel is being delivered.

Restricting air intake makes up for less fuel.

Since, evidently, the carb has some problem (in particular an improperly low float level) all the different metering systems in the carb are acting strange, including the idle system. This might be the reason it's a little bit hard to start.

Starting requires a really rich mixture. Idling requires only a bit less fuel than when starting. If too little fuel is available, it won't idle well and would be harder to start.

Re: cant let go of the choke (mobylette)

ok so what should i do to restrict my air intake?

would tightening the choke cable help it seems awful loose.?

also there is no exhaust on it, would the lack of back pressure also be causing it to die out without the choke being held?

Re: cant let go of the choke (mobylette)

My Moby behaved exactly this same way, until I cleaned the main jet. It was totally (re)plugged. Used a little piece of copper wire to clear the blockage, then shot a bunch of carb cleaner through it to clean up what the wire didn't touch. Runs fine now.

As for the sticking cable, you need to correct that; it's a real safety issue.

Make sure the throttle slide moves freely, and that the return spring is good. If that's all OK, then you need to find out if it's the cable or the throttle grip itself that is sticking.

Shoot some lube like CableLife -70 or Tri-Flow into the twistgrip mechanism. If the cable is dry, lube it. If it's frayed/damaged, replace it. One or several of these will make it work smoothly, and snap back reliably.

Re: cant let go of the choke (mobylette)

i think it may be my spring and a dry cable, where could i get a new spring?

Re: cant let go of the choke (mobylette)

Maybe you misunderstood.

If you need to deliberately keep the choke partly closed to keep the engine running, you are already restricting air intake.

The reason you need to do this is because the carb is not able to deliver an adequate amount of fuel. Limiting how much air can get in helps the engine idle since this forces the mixture to become "richer".

So, it sounds like something is wrong with fuel delivery. Something is restricting fuel. My first guess would be a low float level. It could be other things, like restricted fuel flow through the float needle.


No exhaust pipe or muffler will have no effect as far as starting that thing up and it should rev up to high RPM too... I have run top speed without any exhaust just for kicks and, although acceleration was really bad, top speed actually increased.

In my mind, there's no debate about backpressure on two stroke engines. Too much definately causes high heat and can burn a piston.. but "too little" has no permanant negative effects.

Re: cant let go of the choke (mobylette)

my fuel flow from my petcock, which leaks, seems like it is a bit slow.

how should it flow out?

what i get is like a thin stream, should it be as wide as the fuel hose or is it coming out the way it should?

could this also be part of the prob???

also if that is not a prob. how would i fix the float needle issue?

Re: cant let go of the choke (mobylette)

Fuel should flow from the fuel line in a thick, steady stream, from the "main" tank and from the "reserve' setting.

If flow from the tank is inadequate the symptom will probably be that you sorta "run out of gas" while riding. After a few minutes of sitting there wondering what the hell happened, the bike will start and run fine for a little while. Then it will die again .. mysterious :)

Since your trouble happens at idle where not a large supply of fuel is needed, chances are the problem is in the carb.. like the main jet is partly clogged, or flow into the bowl is _really_ slow.. or the float level is low..

I think you'll eventually have to get into the carb and examine it.. clean it.. adjust it. First take care of any fuel leaks like the petcock thing or whatever.. Also make sure all nuts and bolts are tight. There's no way to tune a carb if you've got fuel or vacuum leaks.

Re: cant let go of the choke (mobylette)

ok ill post again when i have fixed those things

thanx for your help

Re: cant let go of the choke (mobylette)

cool.. no hurry. A big part of moped ownership should be the enjoyment of working on them and fixing them. So much time will be spent doing in that direction that otherwise it's not worth it.

There's much to be said for finding some broken down, obsolete, rusted piece of crap leaning against a dumpster and transforming it into a very useful, reliable, practically unique (these days) vehicle.

I think you DO need an exhaust

joew, I hate to contradict you, especially since I'm quite new at this, but I've been told several times that having an exhaust is critical if you want your two-stroke engine to run for any appreciable amount of time. There are two reasons for this: 1) Without the backpressure provided by an exhaust pipe, a lot of your intake charge goes right out the exhaust port, carrying a lot of oil with it, and 2) you'll suck fresh air in through your exhaust port, which causes the engine to run lean. Running lean increases combustion temperature, and that's the last thing you need when half your oil is escaping. As far as having an exhaust that's too restrictive goes, I think that just fouls plugs and causes "bogging".

Re: I think you DO need an exhaust

well.. the idea that a 2-stroke requires backpressure gets thrown around a lot so i'm not suprised you've heard it a few times.. However, I'd be more than willing to debate anyone on the issue.

As far as the open exhaust port sucking in fresh air, why would it do that? Both hot expanding exhaust gas is trying to escape through the port as well as fresh mixture being pumped up into the cylinder and out the exhaust.. It seems to me that there is no opportunity for anything to get sucked _into_ the cylinder through the exhaust port..

And I'm certain a lot of fresh fuel / oil is surely wasted out the exhaust.. But I do not see how this necessarily damages anything. A whole lot of fresh fuel is wasted on all 2-stokes with your common, stock mufflers too.

Early "high-performance" exhausts were nothing but a header and a diffuser which forcefully sucked exhaust and fresh mix out, without regard for how much of either, other than the maximum..

All that was important was that the resulting mixture trapped in the cylinder was cleaner and burned hotter.

BTW, you ever play with those little Cox TeeDee .049 2-stroke engines.. the ones they use on model airplanes?

None of those come with any sort of exhaust.. nor, i imagine do the more modern 2-stroke RC engines. They are open ported and yet run fine and last forever.. And they run on nitromethane/alcohol..

Re: cant let go of the choke (mobylette)

yeah i love this ped. it is my idea of what one should look and feel like. i am soooo excited to get it going but like you said reviving it is part of the fun. i cant tell you how happy i was when all the hard work i had done and all the time i had spent cleaning pulling things apart and checking/double checking, finally kinda paid off. it is the smallest amount of progress but i was so excited

thanx for all the help

Re: cant let go of the choke (mobylette)

About the 'choke' on a Motobecane (Gurtner).

I've looked pretty carefully at these carbs, and the choke mechanism is kind of a mystery. It's not exactly like any design that I am familiar with, but I do have some idea about it.

It doesn't appear to be a 'choke' at all.. it looks like an enrichener device. That is, it doesn't provide a rich mixture by choking off the air intake, but by opening a secondary metering passage that allows more fuel into the engine.

The mystery is mostly due to the fact that I have no idea how the internal passages of the carb are connected & routed. But since the 'choke' does not appear to have any method for actually choking the intake, I assume it must be an enrichener.

On motorcycles, it's very common to have a lever marked 'choke' that actually controls an enrichener. It's marked as such, as the owener doesn't know (or need to know) what an enrichener is - it works the same as a choke.

cant let go of the choke (mobylette)


By the way, if this is the typical gurtner carb found on most motobecane, the float level is not adjustable by any normal means.

It uses a baloon style float, the kind with the fuel inlet needle as an integral part. No obvious method of adjustment. Replacing the inlet needle & seat involves replacing the float and the float bowl cover.

It might be that the needle is free to be moved up & down within the float, but I'm not willing to find out the hard way. The manual also makes no mention of adjusting or checking float levels.

Re: cant let go of the choke (mobylette)

Mike Scouty McScoutington /

i know this sounds kinda silly and i dont doubt anyones mechanical ability but when i had my gurtner it was acting up when i cleaned the carb and put the float in upside down. could this be the issue? it wont seal right and all that fun stuff.

Re: cant let go of the choke (mobylette)


Thanks for the heads-up..

Unless i know the specifics, I do my best to make conversation about general principles, hopefully avoiding being specifically wrong about a particular carb or bike or whatever. But i'm wrong a lot about a lot of things anyway.

These bikes are different and yet so similar. Without actually seeing a bike you never know what's bolted up to it..


BTW, I've noticed that when you respond to a particular person, your posts are not threaded.. That makes me think you are operating in "Flat View ".

There is an option to use "Threaded View". It's up there to the left of the "Search" feature. Threaded view makes it easy to point answers directly to a specific person's posts.

Pardon me for mentioning it if you already know exactly what you're doing and prefer to do it that way... I know that "Flat View" makes it easy to read all the posts at one time and has it's own advantages.

Re: cant let go of the choke (mobylette)

well when i cleaned it i put the needle end up.

is that correct???

Re: cant let go of the choke (mobylette)


You're right.. I do use flat view most of the time, due to a bug that makes me click every threaded post twice to view it. I do use the "Reply To This Message" link, but apparently, it's not dropping the replies into the thread where I intend. Good to know.

And yeah, I'm totally with you on the specifics stuff. At times, I also post info that is technically correct - but turns out that it doesn't apply to the specific situation. With the myriad of design quirks in this field, no mere mortal can "know it all".

And anyone who thinks they do, is a bigger fool than all of us put together.

If I post a 'correction', it's really more of an addendum. My interest is only in getting good information out to people who need it. It's not about ego. I sense that you have similar goals & motives. Keep it coming man!

Re: cant let go of the choke (mobylette)

yup pointy end up is correct.

I have found a few mashed up needle points because it is easy to put the carb back together with the float not seated properly, so be carefull when you reassemble.

Re: cant let go of the choke (mobylette)

by the way i tightened up the choke cable and i no longer have to hold it in to keep it from dying, i guess it was just a bit old and had stretched a bit.

but for some reason i cant pedal without the engine trying to start... the engine stwitch on the left handle is off but it still wants to start... whats that about?

Re: cant let go of the choke (mobylette)

That is just the way mobies work-

on the outside of the pulley wheel (near the left pedal) there is a rotating switch, right now it is set in the moped position. if you spin it you can put it in bike mode (engine disabled) for when you break down and have to ride home

Re: cant let go of the choke (mobylette)

ok i get it now thanx i feel dumb haha

hey now that i am almost on the road with this ped how fast can i expect to go.

i got it going today and it feels powerful, i have no exhaust on it right now so i didnt really ride it long, didnt want to piss off the neighbors.

Re: cant let go of the choke (mobylette)

was wondering... the mobylette has an ignition key?

i dont have one so what should i do, do i need it?

Re: cant let go of the choke (mobylette)

these forums never worked quite right for me either.. a pop-up login window appears everytime i view a page.. im not complaining.. things are much worse at

Re: cant let go of the choke (mobylette)

It is not an ignition key, it is a fork lock key and you dont need it.

you may also have a strange little metal clip on the gas tank.

That clip worked as a helmet lock. You would clip your helmet into the clip, then turn the forks to one side (thus locking the clip (and helmet) in place.

If you can go 30 you will be doing well

If you are not going that fast, you may want to look into some of the other things you were thinking about...Timing and compression.

I have a bunch of 50v's and I do not think any aftermarket stuff is very available, or worth it.

PS, I have nopticed that my moby speedos display on the slow side a bit.

moby speedo 30mph = 33ish mph

Re: cant let go of the choke (mobylette)

ahhh good to know. i was worried about the key hole.

i would like to get the key just to make it a little more secure.

its to bad also that the mobys are so hard to upgrade.

i was hoping to get at least 27 so i could have the same speed or more than my batavus so at least i got that.

im not complaning though i love this ped.

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