Tuesday, August 17, 2010

FACO power for le peugeot

This pipe has tempted every Peugeot owner since it came up on treats and 77 a couple years ago. Its unreasonably cheap, looks like it should mount with minimal complications, and from the pictures appears to be a halfway decent shape for stock-ish bikes. The scary part is that there is almost no information. I got my first Pug a couple weeks ago, and nobody could say for sure 'I've ran this, its good' besides somebody saying Fred (all your moped are belong to us) had a couple bikes running mid 50's with them, kitted.

So after a couple days of homework, i took the plunge and invested the 45 dollars in it. When it showed up I measured it. Here are the measurements:

Faco Dimensions

It looks to be about the same as a puch proma GP, maybe closer to a Jamarcol.. never measured one. The only dimension that is really wrong is the convergent cone. This one has a sharp taper and is only 4" long. In theory, that should result in narrow powerband that shuts down abruptly, not exactly what i'm looking for on a stock bike.

The other thing i noticed right away were some suspicious-looking spot-welds right in the belly section of the pipe. Since i knew i wanted to build an integrated silencer and i wanted to re-do the convergent cone, I figured i might as well get to hackin' to see whats up with those spot welds.

I also mocked up the pipe on the bike and found out that the mounting brackets are too short. The flange wouldn't sit flat, and the belly of the pipe was hitting the little nub that holds on the flywheel cover. Might be designed for a knock-off of the puegot with a CDI stator, or something like that. Either way, it needs about 9/16" added to each of the mounting bracket arm thingies.

After chopping the pipe in half i found this:
From Pipes

Oh man, that sucks, not only is it almost impossible to remove without chopping a huge chunk of the belly section out, but it is most certainly a major restriction. It pretty much defeats the entire purpose of an expansion chamber and turns this into a stupid looking muffler that doesn't muffle much. If I didn't care, i would probably just cut out the inside of this with a torch or something and weld the pipe back together as it was, and slap an aftermarket silencer on it, but i like skinny long pipes for stock bikes, and this looks like with a little work it could be really awesome.

So i cut out the restrictor, and lost most of the belly section of the pipe. In order to get the integrated silencer to clear pedals and stuff, i had to cock it out so i beveled the cut a bit outwards and welded in a new chunk of belly section, a bit longer than necessary. I formed a cone out of some sheetmetal for the convergent cone, and welded that to my new stinger, which was drilled for perforation. The new convergent cone is a bit longer and has a larger stinger outlet, hopefully giving the effect of a longer duration power band.

I test fit the pipe, and now the angled belly section was hitting the little nub on the stator where the rubber tab bolts on. Easy fix- put the pipe in a vise and bend the header and all the mounting tabs over, so now the pipe is tipped down a bit on the outlet side. The stock mounting brackets should do the trick now also, because i dont have to drop it down to clear that nub anymore. The muffler has to come back up to clear the 2.25" gap between the pedal and the kickstand, so I welded the cone back into the belly section tube with a slight up-kick. I'll have to put a turn-down or something on the end of the stinger to keep from greasing my rear wheel but no biggie.

I've also gone to a smaller muffler canister, 1_3/4" tube instead of 2.25 to clear the pedals a bit more easily. The sound dampening might not be as good, but it will still be better than those proma circuit exhausts.

From Pipes

As of now, its mocked up and tacked together. I'll test-fit it tonight. I've hooked up a 14mm bing carb with a shim to the stock intake, reeds. Hopefully this will have things running well enough for tomorrow night, and we'll be able to do a little shakedown before grand rapids.

UPDATE 8/19:
Mega boner kill, Caite and I had a serious talk yesterday at lunch and decided we should probably pay the power bill instead of going to Grand Rapids. It would be fun, but both the Sachs and Puegeot are in the early stages of tuning and probably not rally-ready, we're both broke, and I have a huge backlog of work to catch up on from summer vacationing too much at the beginning of the month. Maybe if my paycheck comes in tomorrow and is huge, i'll hop in someone's van at the last second, but its doubtful.

The good news is that the pipe fits perfectly. It variates perfectly through the gap between the pedal and kickstand. The bike fired up on the first kick, and revs out like a cross between a wounded cougar and a chainsaw, but something is keeping it from idling, possibly timing, possibly something having to do with the super random assortment of bing parts that i turned into a carb. The pipe is amazingly quiet, like, quieter than a tecno estoril, quiet.

The fan wasn't working in the workshop yesterday (again) so between a kinda-iffy bing needle and lots of exhaust fumes i couldn't get things dialed in before i asphyxiated myself. Pictures and final tuning results later tonight, maybe I'll get the sachs cabled-up and assembled a bit too.

Update 8/23:
Finally got this thing running pretty well after replacing the condenser. Small job turned into 2 hours of beating on a flywheel with a hammer because i didn't have a peugeot puller. Damn. Its running a lot better, but now it seems rich. Its running a 70 jet in a 14 mm bing, which would be huge for a stock/piped puch, but its really bogging out bad on the top end. Methinks timing might be way too retarded at 1.65, or maybe it really is sucking in that much air. The variator is also pretty much useless with the current weighting because it variates way under the power band of the pipe. That needs to be fixed as well. More later

Bonus: the sachs is fully cabled and almost ready to run, the shifter cable is perfect but it keeps slipping off, i'll have to do something about that.

Update 8/24:
Awesome success last night, finally got things running perfect-o, blasting right up to a solid 25 then slowly climbing to about 35... meh, sounds like those tiny little flippy-flappies are choking me out. it four-strokes like a mother when it revs out on the stand.... yep, restricted reeds, indeed.

luckily my patron saint, blaze, lent me some nice generic black plastic reedy things, until i can get some thinner gasket paper and chop up my flap-holes. frabjulous!

maybe wednesday i can duck out of work early and finish the sachs, it is so painfully close right now. shifter, clutch and everything seem to be working good. still have to find a plug for my voltage regulator chinese scooter special, and do a tiny bit of rewiring for the 12v system. oh yeah and the pipe needs a little persuasion as well.


  1. Keep it up Graham! Crazy that you found that huge restrictor in the expansion chamber!

  2. I totally love that you chopped this and took a picture! I was pretty sure there was something in there and you show it in full detail! thanks!

  3. I know this is a bit old so the pictures arent working, but Id love to see how the restrictor came out before I cut into the pipe

  4. yeah man where the pictures of the finished pipe and the restrictions! GREAT POST!