1968 Motobecane 50V (i think) poor compression and spark

Tyler Angeloni /

Jun 03, 2019 11:35PM

hi all i just bought my first moped, motobecane 50v, tried to get her to fire but it would barely jump when i was turning it over with a drill and some starting fluid. new spark plug, adjusted points but it only have spark when it wants to. (i think i has a bad ignition coil). checked compression and it seems rather low a bit less than 90 psi. I've done some research and poking around on the bike and those seem like the 2 areas that need attention, nothing on this bike looks like its been touched all stock. and yes its missing the chain guards :(

Questions for the moped Wizards-

1. What do i do to increase the compression?

2. Could something else be causing my intermittent spark?

3. I'm getting a SHA carb because I've already seen so many complaints on the stock one anything a noob should lookout for messing with this bike?

Re: 1968 Motobecane 50V (i think) poor compression and spark

Kenneth Hill /

kensroswell

Jun 04, 2019 02:38AM

It might be a decompression valve leak (easily fixed with lapping compound) as for the spark, take the kill switch out of the picture (for now) by unplugging the green connector that leads off the external ignition coil.

Absolutely replece the carb with an sha (15.15 will allow you to use it later if you bump the displacement).

Make an auxilary ground from a solid connection on the motor to the frame (as the ground strap from the cylinder/engine pivot bolt is sometimes "suspect") to the frame. Next would be the condenser (under the flywheel).

As for a good bike for noobs, they're no harder than anything else, just do your research, learn their idiosyncrasies, buy the proper tools to work on them, and you should be fine.

ps. Definitely replace the motor mounts before going any further.

Re: 1968 Motobecane 50V (i think) poor compression and spark

Aaron Blair /

aaronb

Jun 04, 2019 04:50AM

I don't think the 50v existed in 68..post a picture...

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