Motobecane exheast emergency

I need help really bad! My girlfriend's 1977 Motobecane Mobylette has a serious exhaust problem. The previous owner stripped the exhaust port (both nut and the threaded portion of the Cylinder) then proceeded to tap a tiny hole as a holder for a screw (I'm guessing to wedge it). after I removed the exhaust to clean it I made the shocking discovery-and now it's impossible to put it back together. The is a serious shortage of parts in Ontario (canada) so I'm stuck for a replacement. Anyone with crazy and creative ideas please post em' I need all the help I can get!!!!!

Re: Motobecane exheast emergency


I don't understand why the previous owner's approach won't work again. What makes it impossible to put back together... did you strip the hole he tapped?

Re: Motobecane exheast emergency

A machine shop should be able to retap the threads.


Live to ride, Ride to work

Re: Motobecane exheast emergency

cant you retap it or use a slightly larger self tapping screw?

Re: Motobecane exheast emergency

It seems like it was a one time only deal because he used the screw as a thread for the nut to bite onto, thus stripping the nut pretty bad aswell. I might try to put it back on again but I'd rather fix it properly because it's my girls ped and I don't want her to be stranded somewhere. Don't get me wrong if it was mine I wouldn't be too concerned!

Re: Motobecane exheast emergency

P.S> Thanks guys

Re: Motobecane exheast emergency

thats a tough one. Exhausts have to be installed right or they end up like that one.. the 4th previous owner might be the one responsible for the original damage and from there it gets worse and worse.. and what repair is now needed sorta depends on how bad it is.

What you should do depends on what you are capable of doing. Are you setup to cut, weld, drill, tap, etc.? If not i'd say think long term, and take it to someone who can return the thing to it's as-new, stock condition.

Otherwise you could drill a few tiny holes and string some safety wire through.. there are lots of similar tricks and methods of temporarily securing a nut onto a bolt. But i wouldn't expect an exhaust-tight seal if the theads are badly stripped and the thing's got a bunch of holes drilled into it.

I have one question about that cylinder.. can the threaded tube part (that the exhaust nut screws onto) be removed from the cylinder or is it an integral part of the casting?

Re: Motobecane exheast emergency

On the motobecane, the exhaust port threads are cut into the parent metal of the cylinder itself. A proper repair isn't very practical, as it would involve something like milling out the old thread and welding in a sleeve with new threads.

Also, unless I'm wrong, the exhaust nut is captive on the pipe, so again not practical to repair. Wonder how they stripped a steel nut and and aluminum thread..?

If I were in this situation, I'd be looking for a NOS top end, and a good used exhaust pipe. Top end stuff shows up on eBay, as do pipes.. and neither are terribly expensive.

As it seems the original parts are a loss, it might not be dumb to just JB Weld the pipe, nut and all into the cylinder. When you get new parts, just hacksaw the pipe off and go about your replacement work.

Re: Motobecane exheast emergency

When I was searching for a replacement for my copper exhaust gasket, I looked at a couple of different high-temp sealants, including J-B Weld, but couldn't find any that were good for more than 600

Re: Motobecane exheast emergency

I re-tapped my euro-kit once or twice and it stopped giving me trouble, but if it got worse i would have gone with a heli-coil or something similar. As far as the JB weld goes, go ahead, that stuff is plenty strong, but only use it as an "added" protector, like in conjunction with a heli-coil. (btw i think jbweld advertises on the back of their package success stories of which i think i remember one person saying they fixed a crankcase or something similar with it

Re: Motobecane exheast emergency

coincidently i was out at the auto store pickin up some junk...

J-B WLED (spelled wrong so I don't get sued)

"The city of Dallas, Texas repaired a cracked Cater-pillar engine block with J-B WLED and saved $4,000.00 plus 30 days down time."

whats a caterpillar engine block? who cares!...if it melts, sue em for false advertising!

Re: Motobecane exheast emergency

a caterpiller is one of those big diesel bull dozers

JB weld held the exhaust on my PA50 just fine that stuff is almost as good as steel

Re: Motobecane exheast emergency

Mike Scouty McScoutington /

if you need the parts i know where you can get them. email me and i will get you the info. the shop here in kalamazoo will sell the copper gasket, they have a nos pipe as well as proformance pipes in stock and i believe that they either have or can get their hands on a new or slightly used good cylinder.

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