Peugeot running extremely lean!

Brendan Connolly /

Hey guys,

My Peugeot TSE, which shares the same motor as the 103, is completely restored back to stock. The only problem is its running extremely lean. I did a plug chop and the plug electrode is completely white. What could be the cause of this? Old gas? Something not set up right in the carb?

Re: Peugeot running extremely lean!

Brent, you may be getting air in through the air box. The Gurtner's have that wacky box, make sure it's tight and not leaking.

Re: Peugeot running extremely lean!

White is not necesarily bad .. grey does mean things are really hot..

So, do you see signs of definate overheating:

Use good magnification and good lighting..

on the porcelain insulator .. see any tiny black spots or spots of aluminum stuck to it? does the surface appear crazed rather than smooth?

look at the edges of the electrodes.. are the sharp, square edges rounded over (melted)?

Look where the center electrode meets the insulator.. There's a type of cement holding it in there.. this cement will "boil" if it's too hot.. the result looks like cement is coming out.

BTW..we're talking about using and examining a brand new plug for the chop.. an old plug is useless.. it has history.


check timing .. too advanced will mimic a hot, lean mix.. So will too-high compression ratio. There are other things that cause what appears to be a too-lean condition.

But hot and lean is where the power is. If it's not too hot, you're ok.

one more thing

Excess gasoline produces a soft black soot.

With a perfect air:fuel ratio in a well tuned engine, the only place any soot should be is deep down.. between the insulator and the metal base of the plug.. way down at the bottom. If you see soot anywhere else, there is at least some extra fuel.

But if there's zero soot down there, it's either too lean or right on the edge... in the danger zone.

Re: one more thing

Brentus Sioux y Cycle /

Tony, that was another peugeot guy with a similar name

Re: Peugeot running extremely lean!

Brendan Connolly /

Thanks for the quick input guys, ill check that stuff out and get back to you later.

Re: Peugeot running extremely lean!



Picture of the plug

Brendan Connolly /

Ok good news, fooled around with the carb, took it apart and rebuilt it and such, tightened the air box, and put a new plug in and did a plug chop. The plug is cocoa brown, as shown in the pic. This is optimal performance and lubrication right? The problem with my carb is that they dont make jets anymore, its a differant type of gurtner carb only found on peugeot TSE's, TSE.R's, and TSM.R's. Can i make it run richer just to be safe? I want this thing to last a while.


Re: Picture of the plug

i can't tell from that blurry pic.. need to see magnified details to properly read a plug.. From the color I would never have guessed that was a new plug prior to a plug chop. But computers and colors often don't mix well.

optimal is what you want optimal to be.. the bike is not destined to be a world beater so there's no reason to tune it to the edge of lean. If optimal is safe, you're safe as far as i can tell from here..

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