Misfiring Peugeot 103

Chris Robertson /

Howdy Folks:

I recently purchased a 1978 Peugeot 103. When it's running properly, it will hit 60 - 65km/h (37.5 - 40mph). A few days after I got it, it started to miss. It sounds a bit like a WWII fighter plane going down in flames (runs for a bit, misses for a beat, runs for a second, misses, etc.). This problem does not happen at idle. It does happen regardless of whether the moped is on the stand or being ridden. Compression is 120lbs/square inch.

Here's what I messed around with before the problem occured (I was trying to get it to idle smoother and eliminate a rattle when it idled):

1. I cleaned the carb. Twice. There was no gasket between the carb and the engine so I put some of that Insta-Gasket stuff on it to create a better seal. I made sure the gasket material is not blocking the fuel/air passage.

2. I changed the spark plug. I used an NGK BPR6HS which, I believe, is the correct plug. Gapped at .030.

3. I took the variator apart and cleaned it.

I originally thought that the problem might be a slipping clutch in the variator. I've eliminated this, though, because I've cleaned the frikkin' thing about ten times now. I've degreased it thoroughly with brake parts cleaner until paper towels wipe clean. I've scuffed all the mating surfaces with 100 grit sandpaper until their shine is gone.

I do know that the original petcock is shot. It will not close. There is a lawn mower fuel valve placed in the fuel line to allow fuel shutoff. Fuel seems to flow at a pretty good rate. The tank doesn't seem very rusty. Sometimes when the ped is on the stand (not running), it will drip fuel (very slowly), sometimes it doesn't. I notice that the occasional, small, air bubble works its way into the fuel line when the engine is running.

Are you still reading? If so, do you have any suggestions?

Chris.

Re: Misfiring Peugeot 103

Ron Brown /

Chris,

Check the color of your plug for rich ar lean and get back to us.

Ron

Re: Misfiring Peugeot 103

Chris Robertson /

Plug looks dandy. Nice rusty color.

Re: Misfiring Peugeot 103

Ron Brown /

Chris,

If this problem started after you did the work you describe, that is a good place to start.

First, the variator has nothing to do with an engine missing so you can ignore that.

Put the old plug back in, check the plug cap and wire for any damage caused by fooling around with it.

Check the carb to manifold for air leaks by spraying with carb cleaner or WD40.

Are you sure you reassembled the carb correctly?

Ron

Re: Misfiring Peugeot 103

Reeperette /

This is probably a stupid thing to ask, but hell...it's worth checking for process of elimination value alone.

The fact that it cuts out only in motion shook lose a memory of tearing a ped half apart (and tearing some hair out over it) only to eventually find the simplest damn culprit...the damn spark plug cap was loose.

Check the connection path from plug to coil, just in case - prolly not what it is, but you never can tell.

-Ree

Re: Misfiring Peugeot 103

also try a better spark plug. bosch platinum is the only way to go. champion and ngk are not very good, from our experience in kalamazoo.

Success!

Chris Robertson /

Thanks for all your input, everyone.

I took apart the exhaust today suspecting I might have had a problem with flow. While I had it apart, I realized that the 'J' portion of the pipe was cracked apart. I removed the 'J' pipe (as well as the baffle) and lo and behold! The ped idles slower, has more power and the awful rattle is gone.

At this point I still haven't fixed the misfiring.

I sat there looking at the little air bubbles that were accumulating in the fuel tubing while the moped idled and wondering where they were coming from. They seemed to be coming from the carb, so I decided there must be a problem there. I initially suspected a bad gasket, but I had already checked the fuel bowl gasket twice. I remember a recent post about carbs having an air bleed in the fuel bowl (I not sure who mentioned this --Ron or Fred, maybe?), so I looked for that. Guess what? A previously unnoticed passage on the top of the fuel bowl! I blasted a couple of shots of carb cleaner and compressed air through the passage and [wait for it]....

the ped runs fantastic now!

Not only that, but with the baffle out of the exhaust, I gained even more speed. This new Peugeot has turned out to be a darling! It will go 60km/h (37.5 mph) on level ground effortlessly.

I did the same "mod" to my other Peugeot and gained about 5km/h (3 mph).

Life is good!

Chris.

Re: Success!

great to hear that! but i bet it's loud w/o the baffle, eh? ;-)

Re: Success!

Chris Robertson /

Actually it idles quieter, and it is only marginally louder when it's running without the baffle. There is still a baffle in the muffler that's welded in place --I just removed the second one.

Chris.

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