Why is my Motobecane 50V clutch area so loud?

This is my first 50V that I've had running so maybe it's normal but it seems loud around the clutch area. Is this normal? It's hard to desribe the sound. It almost sounds like one can rotating inside of another one. I know that's kind of whats going on there but should it make that sound? If it's fairly common, what causes it? Thanks.

Re: Why is my Motobecane 50V clutch area so loud?

Wow, Mine does the same thing and i'm new to motobecanes too. It's a very noisy metallic sound...I'm thinking it may be the bearings rattling around but i sure don't know for sure. I was thinking it's the nature of the beast....i'll looking forward to hearing from others about this too!

Re: Why is my Motobecane 50V clutch area so loud?

ಠ_ಠ Jon Folks ಠ_ಠ /

My 50V is pretty quiet in the clutch area. Maybe you need to grease them bearings up good! Do a search on it, its actually not too easy from what I hear.

Re: Why is my Motobecane 50V clutch area so loud?

Hey,

Yeah, I've got 2 mobies, one has a bad sound coming from the clutch, and the other has an absolutely terrible sound.

I think it has to do with the main bearings, like they are particularly prone to corrosion in the moby engine.

I don't know, though if you are of the religious persuasion, you should pray that the bearings aren't bad, as they aren't (easily) replaceable.

Hope this helps,

willie.

Re: Why is my Motobecane 50V clutch area so loud?

Just got mine running too and it also has a weird noise, but not the same one--you can hear the clutch engaging. Right when it starts to spin, you can hear a little scraping sound, then it goes away when the clutch engages fully.

The thing only has 800 miles on it, so I doubt the clutch pads are worn out. But it hadn't run in many years, so I'm hoping they just have some crud on them and it will go away once I take it for a good long ride.

Hopefully, that will be soon--just have a couple front fork and rear brake issues to iron out and I should be good...

Why is my Motobecane 50V clutch area so loud?

OK, a couple of ideas. Any one else know what causes it and how to fix it?

Re: Why is my Motobecane 50V clutch area so loud?

Hayden Stevens /

I have 8 Motobecanes...My main one is quiet as can be..like, you can have a conversation over the sound of the engine..haha....but one of my other bikes in particular is extremely loud, with this Metalic sound you speek of..It's so loud it drowns out the actual engine sound...Well this Engine went to hell and I brought it back...this thing was seized so bad I had to soak it in marval mystery oil for a week before I could even start to loosen anything up...I to chissel the piston rings out.....well anyways....I am pretty sure that the sound from that engine is due to horribly rusted and corroded engine barings...but I have gone a couple hundred miles on this bike and it works fine..it's just loud....If I'm not mistaken, you'll need some very special motobecane shop tools to get to those barings..( more than just a clutch and cam shaft puller) I tried my best on a junk engine and just couldn't do it....My advice...open up your engine and soak the crank case with marval oil...and put a little extra 2 stroke oil in your gas if you want........Good luck

[hayden]

Re: Why is my Motobecane 50V clutch area so loud?

If you have eliminated all of the other possibilities then you can safely say that the sound problem is bad crank bearings. Any imperfections in the bearing will make a noticible sound (sometimes enough to basically drown out the engine sound). Replacing these is a delicate procedure and does require surgical skill and patience. No special tools required: other than a jaw puller to pull the cases off each side of the crankshaft; a good punch to pound the old bearings out of the cases; a piece of hollowed pipe to pound the new bearing on the crank; and a torch in which to heat the cases and ease bearing insertion. (All of those tools that they show in the repair manual can be easily be substituted with everyday tools and ingenuity).

I've replaced the main bearings on two Moby engines recently and have effectively eliminated the sound problem.

Bearings and seals are available from RCV-Team for 29 euros (shipped) and from time to time, on Ebay.fr (same price).

Re: Why is my Motobecane 50V clutch area so loud?

🇮🇹💦 Of the Loin /

yeah brys and motochick your bearings are fading. My buddys moby which I just got running has the same thing.

Re: Why is my Motobecane 50V clutch area so loud?

Atten ALL! You may need to grease your variator! there is an inverse zirk on the left and side of clutch...the part that spins when engine is running! There used to be a factory grease gun for this but they are rare...almost impossible to find any more. I used a needle fitting from a reg grease gun with the needle removed...it takes 2-3 pumps every 3,000 or 4,000 miles.....this is very important to the health and well being of variator! I have seen many mobys relegated to scrap with out this maint! clean the goop out off the fitting and look in there there is a brass fitting..you should get the point..if this goes on long enough the engine will not swing back from its farthest point of retraction as in after climbing a hil...you will be stuck in high...it may bang back suddenly or you may need it too cool down first! LUBE your varriators! We all know what comes of a lack of lubrication! Peace and Good luck!

Re: Why is my Motobecane 50V clutch area so loud?

Hayden Stevens /

hey......What your saying is good info....but I don't think it's the cause of the loud noise we have.....the engine that I have that is so loud from a bad baring that it drowns out the sound of the engine, doesn't even have a varriator..so that can't be it....but thanks for the tip with the greasing...I do need to figure a way to get that greased on my other bikes..

[hayden]

Re: Why is my Motobecane 50V clutch area so loud?

most likely cause is the crankshaft bearings,

Re: Why is my Motobecane 50V clutch area so loud?

This is most likely what is going on with my 78.

the 79 is whisper quiet.

pisses me off

Re: Why is my Motobecane 50V clutch area so loud?

ernie...this thread is so old!

btw, mine was super noisy too...new engine mounts (jd) bearings and seals, greased the vario...huge difference...tearing it all down...pita

Re: Why is my Motobecane 50V clutch area so loud?

Thanks Matt, yeah I know...

every time I start up the 78 it pisses me off, so I start searching for info. I haven't tried changing the mounts yet, but will do so, as I have a set, but I have taken off the variator and greased up, the vario is very smooth now, but noise is still there...

just dreading having to split the case as everything has been ruled out except bearings...

Re: Why is my Motobecane 50V clutch area so loud?

scott middleton /

sometimes if the either the clutch or the clutch bell plate are just *slightly* out of round, there will be a ting-ting sound. my guess is it's the clutch pads grazing the bell plate. (edited)

Re: Why is my Motobecane 50V clutch area so loud?

Post up a video of the motor running and making the sound as well as video turning the motor over by hand with the spark plug out. That can help figure if it is the bearings or not because if the race is galled it will feel sort of 'crunchy'

A lot of mechanical striking sound can also be traced to poorly maintained ignition, misfiring will allow the PTO to over run the motor slightly and the drive pins on the movable cheek in the variator will sound against the pins on the clutch carrier.

Re: Why is my Motobecane 50V clutch area so loud?

Shit just typed a page of info and lost the draft. F _ _ K

here is a video I posted a couple weeks ago.

Reb, I cleaned and lubed the variator per your tutorial, and it runs smoothly. I didn't film turning the engine over without the plug, but there was some crunchiness to it.

Not sure how I can measure roundness on the clutch, the pads are worn evenly, with zero residue, no glazing, so i think the clutch is ok.

I looked up this old thread, and it sounds just like my bikes. With the 79 you can hold a conversation over the sound of the motor but the 78 buzzes like crazy.

hopefully this link works.

http://www.youtube.com/attribution_link?a=667srrSfY4k&u=/watch%3Fv%3D1vMKpeWx7Zo%26feature%3Dem-upload_owner%23action%3Dshare

Re: Why is my Motobecane 50V clutch area so loud?

If there is any crunchiness to it then you would be looking to do bearings and spi seals in the near future.

Goodly time to contemplate some mods while you have the carter apart

Re: Why is my Motobecane 50V clutch area so loud?

8 Years later....... Bearings are even crunchier!

Re: Why is my Motobecane 50V clutch area so loud?

ernie...bite the bullet and crack the case...bearings and seals need replacing...might as well do the motor mounts too...belt too!

it was a pain but i learned all about my moby and wasn't as bad as when i did my pug...

seals and the motor mounts were the biggest problem for me...

heat the carter in oven for about 30 minutes, slip the inner part of the seal (metal facing into the case) into a small socket then line it up and use a bigger socket to tap them (gently) in...

total cost to do all my stuff was about 80 bux...

i couldn't stand the noise it was making...seriously loud!

i saw your vid...sounds exactly like mine did btw... (edited)

Re: Why is my Motobecane 50V clutch area so loud?

scott middleton /

buy an extra set of new seals as well. you'll ruin the first set trying to install them. (edited)

Re: Why is my Motobecane 50V clutch area so loud?

sounds like you have experience with these seals?

good advice.

Re: Why is my Motobecane 50V clutch area so loud?

use a little more care then this guy..

here is a good vid from tomahawktuning...

Re: Why is my Motobecane 50V clutch area so loud?

btw...make sure you install the new bearings the right way...the curved inner race goes towards the crank face...tomahawk presses them on the crank...i freeze the crank and then heat the bearings in the oven...they slide right on then...

Re: Why is my Motobecane 50V clutch area so loud?

scott middleton /

yes, yes I do! they are a bitch to get in straight without bending the sides. chamfer the lip of the case, makes it easier to get them in straight. after you've done it a few times, it's not so bad, but the first time is tricky. (edited)

Re: Why is my Motobecane 50V clutch area so loud?

cause it's a spinning piece of shit

Re: Why is my Motobecane 50V clutch area so loud?

Get spi seals 15x21x4 SC - they are single lip with rubber outer not steel so they are more forgiving going on and seal well. If you put a scratch in the casing with the old seal removal then they will leak at the scratch with steel on aluminium.

Decades of practice has told me this is spi seals on the easy way for me:

http://mabecanemobylette.freeforums.org/viewtopic.php?f=27&t=1429

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