Motobecane 50v 1978 trouble

So I road it for a while off and on one day, then I turned it off for a bit, tried to start it again and it wouldn't for some reason, so me and my friend ran with it while I held the starter lever and gave it gas and after a while it finally started. I figured out that it was something in the 'clutch' that wasn't catching when you tried to start it, it would kind of catch but not enough. Then I tried to start it again a day later and it started to catch like it did before, but this time it wanted to start but for some reason it just kept back firing over and over, it's been doing this for a few days now. I checked the timing and it's perfect, what else could it be?

Re: Motobecane 50v 1978 trouble

Hayden Stevens /

I think I know.....the "starter Lever" you speak of is the decompression valve...You hold that lever until the engine starts to turn over, once the engine is turning over fast enough you want to let go of that lever (this is the lever on the right---the left lever is the choke)...Keep peddling until it starts, you may want to rev the throttle only a little to get gas into the carb...you can also play around with the choke, but I never do on mine..

If you were doing the above..I would check that the decompression valve on the cylinder head is sealing correctly.....

Check on this stuff before we go any further on what might be happening...

[hayden]

Re: Motobecane 50v 1978 trouble

is it out of gas?

Re: Motobecane 50v 1978 trouble

I've started it many times, and when it started it would start right up in a second. So, I know I did all that stuff right, to get into the decompression chamber (on the left side, opposite of the magneto) you need a special tool made by motobecane and I don't have it. Do you know of a way to get it off without the tool?

Re: Motobecane 50v 1978 trouble

Any ideas of why it's backfiring?

Re: Motobecane 50v 1978 trouble

🇮🇹💦 Of the Loin /

is the belt tight? has it been progessivley harder to start until one day it didnt?

Re: Motobecane 50v 1978 trouble

A 50V is a piston ported engine. Did you break a piston skirt?

Was your oil mix right?

Re: Motobecane 50v 1978 trouble

I know the oil mix is right because I ran it on the same tank for a few days. And no, it has always been very easy to start until that one time that it was very hard to start, then sometimes it would randomly start fine, then I tried to start it again after a day of not starting it and it just backfired...

Re: Motobecane 50v 1978 trouble

Hayden Stevens /

Maybe there's a bubble in your fuel line...that would make it damn hard to start and would probably make it backfire too

Re: Motobecane 50v 1978 trouble

Well I got a flywheel puller and took off the cover to the clutch, I found out that one of the arms that pulls out had a lot of tention and didn't pull out easily. So I lubed it up and it pulled out freely, I put it all back together and now it did catch but I could hear a clanking noise and it still didn't move steadily. I took it off again and found out that one of the springs was stretched out, probably causing the arm to jolt back and forth so it wasn't grabbing it like it should.

It did catch better than it did before but it still backfired... would it not starting and backfiring be caused by the clutch not grabbing as steady as it should?

Would getting new springs fix the problem or should I not even waste my time and look for a different problem?

Re: Motobecane 50v 1978 trouble

For the Backfiring try different plug or at least blow it out . Also check for a plugged exhaust port. You are right in checking the timing still can be .

Re: Motobecane 50v 1978 trouble

Clean your plug, clean your points, check your point gap.

Rusty

Re: Motobecane 50v 1978 trouble

Well I've tried 3 different spark plugs, it's not that, the muffler is not clogged, and i've checked the timing... I guess I'll clean the points and check the gap. Thanks.

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