This simonini circuit pipe can be a nice little blasty pipe but it takes a little bit of work. In the header of the pipe you’ll find a little restrictor that can easily be dremeled out. Once that’s out the pipe will be pretty usable, strong low and mid range.

That said there’s still some restriction in the pipe. I’m used to seeing silencers formed off the stinger by a perforated tube surrounded by fiberglass. This one uses a different design. It’s just two 2 short offset pipes. The stinger has an internal diameter of roughly 13mm and the pipes in the silencer are one 9mm. As the bike get’s into the higher rpms it’s unable to bleed off the exaust the bike is generating and you hit a wall.

I kept the design of the silencer the same on mine and I replaced the small 9mm pipe with some bigger ones that were closer to 17mm. I figured they still serve their purpose of quieting things down, but would no longer serve as a limiting factor.

Well that did the trick, it’s only slightly louder I still have decent low-end and the bike doesn’t hit a wall when accelerating anymore.

Well I think I’ve got my problems figured out with the Peugeot 50cc Racey Kit. On a whim I thought I’d throw a different pipe on and see how it’d perform. I had a spare RGD pipe that I was planning on using on a liquid cooled project I was saving for this winter.

With the new pipe on the kit really opened up. Low end kind of disappeared, but from mid to high the kit rips. I was doing mid 40s without much difficulty.

A clutch pulley would fix the low end problem, but I’m going to see if adding another star spring would help out.

So I’ve been running the 1977 50cc Peugeot kit that I did a video on a few weeks back and here’s what I’ve found so far.

• The Simonini needed a bit of modification in order to fit properly and use my pedals. No big deal though I’m used to having to modify the majority of pipes out there in order to keep pedals. That’s just mopeds!
• I should be running a block of swiss cheese for my bottom end, because I’ve got an equivalent amount of air leaks at the moment with my setup. My old crank seals both leak, the quiksteel I used to fill in around the transfer ports is leaking. The split in the case halves might possibly be leaking.
• I’ve gotten the kit up to 40mph so far, it pull pretty decent up into the 30s and hits a wall at 40. I feel that it should be much faster and that my air leaks and sloppiness are most likely the culprit.

So at present I have everything torn down and I’m going to try and get it back together leak free. Since I’ve got it apart while I’m at it I’m going to open up the intake some more and modify the skirt on the cylinder and possibly the piston for some better flow on the boost port.

And I did a quick port map while I had things apart too…

1977 Mopeds Peugeot 50cc Racey Kit port map