Hello! First post, and a Puch exhaust question.

Well hello! First post here! My first experience on a motorized 2 wheel was a couple years ago on a friends Honda express. I knew I wanted one eventually. In february I put an add out on CL looking for a moped for 300 or less. A guy wanted to sell me 2 for $300. I said "great!" Picked both them up, sold the non-working one for $350 and was $50 ahead on my first purchase. 1978 Puch Newport L. She's a beaut ain't she?

Drove really well when I got it (basically stock), going around 29mph. Streets here in Des Moines, IA are almost always 35 if not 45, so I have been on a journey to get her up to speed. I'd love to get 45-50, though I'd be satisfied with 40. This seems very do-able by the research I've done. To start, I invested in a new 15mm bing carb and intake, as well as a estoril with side-bleed from treats.

Carb and intake install? Piece of cake. The exhaust though? The install has not been as straightforward. After searching the site, I haven't been able to find a straight answer. I'd appreciate any pointers from folks who've been in the same situation.

I removed the pedals because right away I could see they were going to be an issue. I'll get one of those 260mm pedal crank shafts on treats. Out of the box I tried to get the exhaust header to sit flush against the exhaust port, but no luck. I noticed the new header's dimensions were larger than the stock pipe, so I did a bit of grinding which helped. I'm just a mm or 2 away from it seating properly. What seems to be in the way is the moped's exhaust mount (sorry, don't know name) that extends from the pedal shaft. Another developing problem are the threads where I bolt the exhaust to. With all my trial and error fitting, the threads are starting to flatten.

What is best practice for getting this pipe to fit?

I'll also say that I do not have a welder though I may be able to borrow one. I also have a metal fab friend who may be able to lend a hand if I really get in a pinch.

On this subject as a whole I am a novice at best... so please be kind:)

with gratitude,

tyler (edited)

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Re: Hello! First post, and a Puch exhaust question.

You need to bend the header so it will sit flat on cylinder. I use a sewer grate right outside my house to bend them, just bend a little at a time. You’ll need a hi flow bing filter and high 60’s jets. Was their a 14mm Bing on there?

Re: Hello! First post, and a Puch exhaust question.

Grind the holes out enough to let the flange slip into the studs. If you’re banging it on the threads, that’s not good. Studs can be easily replaced if you need to.

Also, get that welder friend to help make a solid mount. I used some 1”square tubing to get a really solid grab on the side of the chamber and bolt onto the mounting arm.

It takes some measuring and grinding. But totally worth it to not have your pipe swinging around on something sketchy.

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Re: Hello! First post, and a Puch exhaust question.

Make sure to re-jet your carb so you don't seize the engine.

They don't come tuned for your bike

Re: Hello! First post, and a Puch exhaust question.

Thanks! I'll give that a try. Do you heat up the pipe at all, or just bend it cold?

There was previously a 12mm bing and intake. I have jets in the 70's, but may need to pick up a 60's set as well. I need to look into air filters as well. Tried out a mlm velocity stack, but it did not fit inside the space.

Thanks for the help!

Re: Hello! First post, and a Puch exhaust question.

Hey Aaron,

Thanks for the tip. I've got some 70's, so hopefully I picked the right range. We'll see!

Re: Hello! First post, and a Puch exhaust question.

Hey there papa, I think I know what you mean, but I'm having a hard time orienting myself on this picture. Have a different picture handy? Thanks for the suggestion!

Re: Hello! First post, and a Puch exhaust question.

That exhaust is major overkill if you're using the stock cylinder. I would recommend a circuit pipe instead like the Proma.

If you're set on that pipe. then follow advice above about slightly widening the holes on the exhaust flange to more easily fit the studs. Flange will probably have to be ground down quite a bit to fit stock cylinder. Make sure you are using a new exhaust gasket, preferably one that matches the diameter of the pipe, like the 65cc kit exhaust gasket.

Once you've got the flange to fit, tighten down the exhaust nuts to torque while supporting the back of the pipe with your hand. If the frame pipe mount interferes, lightly pull the pipe outward for clearance and see if you can get the nuts torqued down that way. It is recommended to use tall brass nuts on the exhaust like these.

With the nuts tightened on the flange, you now want to manipulate the pipe to line up as close as possible to the frame mount. Use Mapp gas to heat the pipe somewhere along the header where you want it to bend. Heat it nice and evenly until it is red hot, then gently but firmly bend the pipe to the position you want and hold it there while it cools. Next loosen the exhaust nuts and remove the pipe, then replace it and check that is has held its shape.

Always tighten the exhaust stud nuts on the flange down to torque first while supporting the back of the pipe, then brace or mount the back of pipe where it naturally rests. You do not want any sort of pressure from the back mount, it should only support the pipe's weight.

Lastly, click "Flat View" at the top of this thread, it's way easier to read this forum that way.

Good luck!

Re: Hello! First post, and a Puch exhaust question.

Mike, wow thank you for the detailed step by step. I appreciate you taking the time to type it up. I've got an order shipping from treats that includes those tall brass nuts- thanks for the suggestion. (I was wondering how that was going to work since my socket doesn't fit in that space!)

Looking forward to giving this technique a try. Have a great weekend!

Re: Hello! First post, and a Puch exhaust question.

I love your movies they are funny

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