1977 Motobecane 50L... a "little" sluggi

My motobecane has recently been completed with the addition of an airbox... but its top speed is 15mph? I need to know how to fix this. My friend says the engine block needs to be replaced, but the ppl on the forums say it needs to be cleaned... which one is it??? i really need to know

Re: 1977 Motobecane 50L... a "little" sl

also i need to know how the whole thing is wired... the mess in the headlight is so confusing... ive opened it once and closed it two seconds later

Homework for Arthur

1- Check compression

2- Check Spark

3- Check timming

Here is the required reading

freds guide


motobecane timing


shop manual (with wiring diagram)


Re: Homework for Arthur

another good idea is to check the exhaust. an exhaust thats clogged with grime/oil/carbon can slow down the moped alot. i had just cleaned mine out ( i have a motobecane 50v) and its alot better now that its clean. what i did was i sprayed the inside if the exhaust ( after removing the exhaust cap and baffles) with brake cleaner then let it sit for a while (over night would be best and put it in a bucket of some sort because it can really make a mess). let it dry then reassemble and attach.

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