Peugeot 103 cuts out coming off of idle

Hey all,

I just got a peugeot 103 SP-U3 for cheap. I got it running pretty quick with some filing of the points, but it still has issues.

It has a dellorto SHA 16.16 on it, with a 72 jet, and a wire mesh air filter thingy.

First off, it idles a little rough. It’s lopey and erratic, and dies randomly sometimes. Also if I twist the throttle, it starts cutting out. If it doesn’t die, it eventually picks up and revs all the way out, running really good in the top range.

If I pull the choke about half way, it starts idling really well, and gives smooth power immediately when i twist the throttle. But then it starts 4-stroking before it can rev up high.

I’m guessing this means that idle is too lean? But there’s not any adjustment on the SHA carbs for the idle mix. Has anyone else had any problems like this?

Re: Peugeot 103 cuts out coming off of idle

Your jetting is wrong. You adjust the mixture by changing jets.

Re: Peugeot 103 cuts out coming off of idle

on a sha the hole below your throttle slide is your idle circuit, shove a wire thru it, i got the a similar issue thinking of drilling mine out bigger.

Re: Peugeot 103 cuts out coming off of idle

Thanks for the reply! I was under the impression that the jet adjusts the mix at WOT on these carbs and not idle? The WOT mix seems to be pretty good...

Re: Peugeot 103 cuts out coming off of idle

Thanks for the reply! I tried to shove a wire in that idle hole to unblock it but it didn’t seem to help. How would I go about widening it? would I have to have a 100$ carb drill set?

Re: Peugeot 103 cuts out coming off of idle

Josiah Radebaugh /

Check this

Screenshot2019-05-21at9.49.12AM.png

Careful not to snap the bit in there. (edited)

Re: Peugeot 103 cuts out coming off of idle

Too much carb and jet. This is stock,right? That's enough carb for a 70cc kit with performance exh.

Also,install a good airbox.

Re: Peugeot 103 cuts out coming off of idle

Other than clearing gunk and dirt from the idle passage hole I DO NOT recommend that you cut the casting hole bigger. These carbs work great out of the box and thinking that "cutting the hole bigger will give me more gas" is just absurd.

All that will do is the need for more vacuum to pull the idle circuit.

If its not idling consistent you may not have the required vacuum to pull the circuit through the idle orifice.

Or if it is idling rough then dying after a bit then the circuit has too much vacuum and you can help this by removing half of the screens from your filter thingy.

Re: Peugeot 103 cuts out coming off of idle

Thanks for all of your help!

I got myself a #71 drill bit from mcmaster and drilled the gunk out of the idle hole. I’t mustve been a lot of gunk because the drill wouldnt fit in the hole at all without actually putting the bit in a drill chuck and drilling it out.

I popped it back on the bike and its idling and running perfect! A perfect putt-putt-putt sound! The cutting out problem is completely gone too!

Once again, thank you all so much! This forum is the best. (edited)

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