Motobecane 50V engine problems

Christian Hanner /

Cosmetically everything is fine.

But , looks are deceiving...I believe I have some form of engine problem(s) . things I have done since receiving it:

I purchased it 3 years ago at an auction for $3.00

I've cleaned all built up grease and dirt from it(sos pad & simple green).

I have installed:

I put 2 new tubes and tires on it.

I have a new autolite 414 racing spark plug and

a new spark plug cover/connector

I put a new petcock/fuel valve and fuel line hose on it.

I have the fuel valve set to on.

I put about half a gallon of fuel in it.

Mixing ratio 4 oz. 2 stroke oil to 1 gal. gasoline as per a repair manuals rating for the motobecane 50V.

I tried pedal starting it, then I held the choke lever in and tried to pedal start it. Both times the engine shook real hard almost as if it were loose on the frame but it seems very tight to the frame. My guess is the former owners ran it till they killed it. Now how do I approach the engine problem?

Parts I have in case its an engine problem:

all new: gasket kit , piston rings, head gasket, air filter,

2 points, 1 used condenser. and an original Dealer toolkit.

Note: I have all this but only have general maintenance for engines in general. thank you for anytime alloted for your positive reply to this thread, Christian Hanner


Re: Motobecane 50V engine problems

Leon Swarmer /

Looks like a keeper.

I don't know French bikes but it certainly sounds like timing issues. is the flywheel tight on the crankshaft?

is the timing right?

others know thse peds better..but I'm on line now/

tool kit

Dave Chudak /

where did you get the dealer tool kit?


Re: tool kit

Christian Hanner /

I got the tool kit off of ebay. from a guy named joel.

ebay id wilbursantiques, don't quote me on it though.

he seems to have a lot of them, but they cost a mid-sized car payment to obtain and are rusty.

I believe its the toolkit board No.2 in the mobylette manual.

take care, Christian Hanner

Re: Motobecane 50V engine problems

Christian Hanner /

who can I talk to about timing issues that knows the french bikes better? also an update since my original post.

The more I try to kickstart it(pedal start it) the more it sound like it wants to run(ever see that movie or read the book Christine by stephan king?), seems pretty cool but still not totally turning over. help from anyone Is and will be much appreciated. Thanks for the replies, Christian Hanner


Dave Chudak /

hey man .. i cannot find any tools on ebay.. let me know if you see any more please.. i desperately need them...

my mobylette won't start either... my clutch seems to be frozen in time... will not engage..... so i get no engine movement at all....

does yours spark? touch the plug to the head and pedal... any spark??

tool pleassssse.. help me find some.. pleeeease.. hehehe..

Re: tools

Christian Hanner /

I am very convinced mine has spark as I have seen the lights go on for the first time ever, although a dim beacon they were. they would go on if the headlight was switched on and I tried to kickstart it. I think mine is almost started, but it just doesn't fully come on. Dave has yours ever worked while in your possesion? just trying to understand how you are sure its a clutch problem. I read someones (keith hannah) blurb on their moped army page. He has the same motobecane model as I do and the start of his story sounds like mine, I acquired Mine in unloved condition. he said on his page he cleaned his carb and then his ran right.

If you know how to start a motobecane 50V please clue Me in 'cause I've been going about this rather blindly.

I'll contact the guy I got the tools from and see if he's got anymore for sale. Thanks for any encouragement you can lend.

Fellow Motobecane Man, Christian Hanner

hey christian, how about this

Dave Chudak /

hey christian... i think you have found yourself a motobecane repair buddy...

i have just got my mbk in pretty rough shape too, for free though.. not a bad deal.. i will need some guidance along the way, as i am sure you will too, so how about we buddy up to fix these old beasts.....

my email is

the most i know about starting an mbk (because i have not started mine yet) is that you need to hold the decompression valve button down, get the pedals going, and then let go of the button...

try this though... take out the spark plug... leave the wire connected..... now touch the metal tip of the plug to the engine head.... does the plug spark? if so you are good to go....

my clutch seems to be sticking... when i pedal, the engine does nothing.... i dont think it is seized, i think the clutch weights are rusted.... i need the tools to open the clutch though....... please try to get in touch with the guy that sold you his.. that would definetly help...

well... i think this could be the beginning of some sweet motobecane restorations.....

Re: hey christian, how about this

Christian Hanner /

I totally agree with your buddy plan.

I could point out some things that might ease you MB towards health that are inexpensive things I did.

I bought a gallon of simple green concentrate $8.00

I bought a large can of WD-40 (don't recall price)

I bought dust off canned air(any brand will do)

I grabbed a few SOS pads from under kitchen sink(steel wool impregnated with Detergent stuff).

also grab a few rolls of paper towels (i'm partial to Brawny Brand). all of this probally will cost $25.US / 30.CANADA

the simple green(mixed 50SG/50water and sos pads + paper towels for simple green all this is your degreasing/derusting agents.

WD-40 is your lubrication where things are rusted or just gunked up.

sos pads are also used to polish chrome or nickel plated so by rubbing metals with sos pad sprayed with simple green, the pad will get foamy and kinda dirty looking, just let it set then polish it with paper towels.

this is a good starting point for anything(moped, bicycle, lawn mower) that has sat for an excessively long time without usage. Dave I'll email you more Stuff.

Thanks for the buddy plan idea, Christian Hanner

Haven't read all posts,but,

.........I would look for the variastor to maybe be frozen(rusted up) if it's shaking like moving the engine to and fro.

Check the clutch/variator operation. don-ohio


Dave Chudak /

i have pretty much cleaned up the ped... i will try that green degreaser though.. sounds good.... i have already taken the front wheel off, and am going to take apart the brakes for a cleaning and lubing... i will be taking everything off of the frame, and sandblasting it soon.... then repainting it... i have a new air compressor, and sweet detail airbrush, so i am going to try to do a sweet job on it....

going to need to rebuild the shocks too... i may try to customize them and add an pneumatic shock, as well as a new spring.... going to have to do some research on that first... once i find a working combo, i will let you know, so you can try the mod if you like.... lets just keep adding to this thread, so other people with motobecanes can join in...

thanks also to don, for adding some knowledge to the thread... he's a great asset to the army..

I will need some tools to take apart the motor, so i will wait to start the engine and clutch rebuild until i get some proper tools... someone wise always told me "use the right tool for the right job" and so i shall wait for the tools...

i need to construct a seat, or find an old one to restore... if you see one floating around, please let me know, and i will buy it... i am good with vinyl apolstering, so i should be able to restore one nicely...

i also need a kickstand if you see one.....

Re: kewl

Christian Hanner /

for those parts you need, go to ebay teal green kickstand.

also from the same seller a seat, not in best shape from what I saw, in think you got a day till they close.

I emailed don directly hoping he could jump into this one.

In my opinion based on what I have seen people shy away from things that aren't easy...thats why you see more threads about everyones tomos or puch or honda and not so many on the motobecane. The motobecane was discountinued in 1986, all those others are either still in business or have a strong aftermarket business.

We need to find or create a strong aftermarket parts network.

lets try to build a list of all manufacturers or suppliers of parts for the motobecane. Try including addresses telephone #'s email addresses and websites when available.

The reason you find junked or parted out motobecanes in because there is a weak support system (ie: lack of parts suppliers) everyone include any input on this subject.

Thanks for uniting, Christian Hanner

good ideas

Dave Chudak /

that is a good idea.. it would be nice to have a motobecane information hub, where people could actually get all the info they need to fully service the bikes... the manuals never cut it... you need experienced advice, from people that have serviced the bikes... there has to be some out there....

you also need people willing to fix the damn things... they are harder to service than the average bike, because special tools are needed.... but why has a tool manufacturer not stepped up to make re-production tools?? i should get my buddy who is a machinist, to make a dozen clutch pullers.... i just need one to look at, to reproduce it. i have to buy a mbk tool kit...

i think i will strip the entire bike down to nothing today... its a lazy sunday, and i have nothing to do... i will take a bunch of pictures of it, and post them on the guelph moped site.

the site is very slow right now... i have to do a re-design of it this week..

i will add a motobecane information section to the website too... so we can start to propagate motobecane repair info on the web..

I'm tearing her apart...

Dave Chudak /

today (sunday) i went on a rampage to dismantle the bike

i have dismantled the:



all the wiring and cables

engine, carb, variator, magneto

electronics and spark wire module

all the cosmetic trim

the chains and belts

i have the rear end of the bike left pretty much... then the frame is going to get blasted with sand, primed up, and repainted...

Re: I'm tearing her apart...

Christian Hanner /

sounds like a major tear apart. I've contacted the guy that I got tools from, still haven't heard back. has some tools, not sure what exactly. But they are kinda pricey.

Later, Christian Hanner

teal green kickstand??

Dave Chudak /

i cant find the kickstand on ebay.. which user??

i also want that seat...

i have done so much today.... i not have the carb off, and the top of the engine head... totally carbonized... i cleaned it up, and cleaned the decompression valve...

i will take some pictures soon...

Re: teal green kickstand??

Christian Hanner /

just type motobecane into ebays search. it came off a 1978 motobecane. hope that helps Dave.

talk to you tomorrow, Christian Hanner


Dave Chudak /

I ended up watching the toronto/ottawa hockey game, and taking apart the carb to clean it...

Its a GURTNER carb, stock to most of the motobecane/mobylette bikes..

for a 33 year old carb, she is looking mighty sexy now that she has been cleaned... i spend a decent 2 - 3 hours performing the cleaning... it was pretty gummed with grease all over the housing...

there are 3 pictures (all after cleaning)... the first one is disassembled... the other 2 are assembled...

i have to order a rebuild kit, for all the gaskets, and i think i will buy a new jet, even though this one appears to be nice and clean....

now i know this carb.... so if you have questions, lemme know....



Dave Chudak /

here is the picture 2 of 3



Dave Chudak /

here is picture 3 of 3..

if you have any questions on mbk carbs, lemme know


Starting a Motobecane...

Dave Chudak /

Directly from the owners manual:

"The operation of 3 controls is necessary when starting the engine.

The choke control lever.

The decompressor control.

The throttle twist grip."

ALSO ... make sure the engine stop button is not in the "off position"... make sure it is ON.

For manuals go to

go to the "moped repair" section.... everything you need...

i hope yours starts christian.... good luck... ps.. like my carb cleaning??

wrong plug christian

Dave Chudak /

i think you are using the wrong plug christian.. check the owners manual...

i bought some champion L86-C plugs

(they are the same as L86, the C is for coding purposes)

i would try that..

Re: Motobecane 50V engine problems

Hello. I have a motobecane v51... i had the same problem.

1 - find the motobecane owner manual and the motobecane repair manual.

2 - check if you have good spark.

3 - clean the carb.

4 - see my new topic instructions to clean the points.

with the manual and some friends opinions here in this great forum i put mine running, it was stopped for a couple of years.

see my bike pics at

Ricardo Oliveira.


Great photo, but could you please resize it to be smaller next time? I'm working on implementing a system on the forum where it automatically resizes photos but it's going to be another week or so. The bandwidth bills for this site are getting out of control and 10% of the traffic is coming from forum attachments.



Do a detail on Carb removal and clean up.

Christian Hanner /

Very nice carb cleaning job. Does yours attach to a black air box?, as most of the mbk's do(it looks kinda trapazoidal and sits right against carb). If yours does how do you detach it from carb without hurting it? its made of some sort of plastic.

Dave, Please do a detail of the carb removal and clean up.

List what tools you used to do the job.

what did you use to clean it?

how long might this take someone to do?

a detail outlining these things would help many greatly.

I know I always have concerns of using the wrong tools,

Plus I worry about damaging the carb parts as you don't find replacement parts easy.

P.S. My neighbor who is vaguely into motorcycles suggested I simply use WD-40 to clean out my carb. anyone with safe results from this jump in.

Christian Hanner

Re: wrong plug christian

Christian Hanner /

A detail of why I have an autolite 414 Racing Spark Plug.

First I looked in Champions spark plug book

for my model Motobecane which is a 50V.

it suggested an RL86C or an L86C, as it did for most similar mopeds, But the damnedest thing is I could not find one anywhere. Which lead me to an Advance Auto Parts store.

I asked the attendent there and of course they didn't even sell champion plugs, but they had the crossover to it in Autolite and some other no name brand. I got an autolite plug because it had a 2 yr Guarantee to work from point of purchase. and thats why I have an autolite plug eventhough my plug search started out for a Champion RL86C/L86C.

Hope that explains the reason I have the autolite plug.

Christian Hanner

Carb Cleaning Procedure

Dave Chudak /

To clean the carb, i started by taking it off of the engine... it is simple to see what need removing to do that.. just remember what you did, so you can reverse the process to get it back on...

after i got it off the bike, i put some paper towel in the open parts of the carb (air intake, choke, etc..) to keep the dirt out.....

then i sprayed it with wd-40 and scrubbed it like a mad man.. this took over an hour to get all the grease off, that had built up over 30 years.....

Then i used silicon lube (you could also use break disc cleaner, or something with high solvent content...) i sprayed it all over to melt away the rest of the grease..

then i started the disassembly... i took the fuel filter bolt out to access the fuel filter and float bowl... i lightly sanded the needle of the float bowl because some deposits had built up... i also cleaned inside the float bowl, and fuel filter chamber with wd40....

There are severy tiny screws you can remove on the carb to access airways which help clean the carb... the manual recommend a jet of air to clean the carb, but wd40 worked well to break up any grease... and my air compressor is not here right now so i didnt have the option....

the jet, i will clean soon... only in solvents, with tiny plastic brush.... or i will buy a new jet....

The whole project took under 3 hours.... i recommend this to anyone... simple to do... pretty hard to mess it up.... all i need now are a new set of gaskets for the carb,,, then i am set...

Air Box Missing... making a custom intake

Dave Chudak /

As for my air box, there was never one attached to the carb when i got it...

i think i will be constructing a custom intake system for this carb using a k&n universal filter.... then i will get a better exhaust system, and upjet for better performance.....

finding a stock airbox would cost me some money.. i would rather customize and make it better than the original parts...

I believe the stock airbox is held on by a bolt, in the center of the box... remove the bolt, and the box should just come off... there is only a lip for the airbox to sit in... and a bolt in the center... not sure about it though.. check the repair manual..

Motobecane Huret Speedometer question...

Christian Hanner /

On my motobecane 50V I have a huret speedometer that has mph markers going up to 35mph , can anyone tell me If this is telling of what speed carburator/variator my engine has?

I've read alot of 20, 25 and 30mph so I am led to assume that Mine may be a 30mph model. I also have seen speedometers for sale but they always go up to 25 or 30mph.

If anyone has the answers to the question, add to this thread or email me

Thanks, Christian Hanner

Re: Air Box Missing... making a custom intake

Christian Hanner /

I looked into it and also have my oem airbox intact and the model I have is attached by a spring clip.

there were 2 oem airboxes one rectangular one and the last one a trapizoidal thing that is clamped to carb by spring clip.

If your's will some better performance make a second one for me, Buddy :D , I almost have you a dealer toolkit .

talked to the guy twice today.

Talk to you later, Christian Hanner

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