1975 Puch Maxi rebuilt but has very low speed/acceleration issues

Hello all,

This is my first moped and rebuild experience and while I do not have any prior mechanical experience I read many of the manuals, guides, and forum posts which has helped me get my bike running again.

However I am experiencing a few issues that I hope you guys can help me with. Here is the situation:

Setup:

- 1975 Puch Maxi Deluxe (Bombardier version)

- E50 engine re-built and cleaned with new seals, circlips, and gaskets

- Stock exhaust that has been cleaned however could not get baffle out to clean as it is stuck

- New stock air filter box

- Original Bing 14mm Carb rebuilt and cleaned including:

o New banjo bolt and gaskets

o new plastic float, float needle and float pin that is currently adjusted to be parallel to the float bowl rim

o new atomizer (2.20) and jet (64) that matches stock sizes on the bike

o needle is set at 2nd position from top

- Points are not new but were cleaned and gap set correctly

- Timing adjusted to get as close as possible to 18mm before TDC (might be off a little as I do not have a timing light but I cannot position the stator further to get closer to TDC)

- New petcock, inline fuel filter and fuel line.

- Condenser looks okay (original soldered version)

- Compression is 100 psi on cold engine

- Bike currently hardwired for spark only as one of the other electrical wires was preventing spark

- New spark plug – NGK B6HS

Issues:

- Bike will start on first kick most times and will idle only with choke in up position. Will not start with choke down.

- If you push the choke down while riding, the engine stops.

- Seems to run similarly with or without stock airbox attached but if you cover the airbox hole to the carb it kills the engine.

- Turning the throttle does not seem to increase the speed at all or very little. WOT causes engine to die most times. Very slow.

- Did a plug chop and it came out covered in matte black carbon, was dry and not wet – too rich?

Questions:

- Where should I start in order to fix the acceleration issue?

- How can you tell a weak spark from a strong one? I can see a blue spark when I hold it against the cylinder and pedal but not sure if it’s a strong spark.

- Should the points be replaced if there is low power? The condenser?

- I checked for air leaks around the Carb while the engine was running and didn’t find any but not sure if my compression is good at 100 psi?

- When I put the piston back together, the two little clips that hold it in on either side were facing different ways, is that a problem?

Thanks in advance for your help!

Re: 1975 Puch Maxi rebuilt but has very low speed/acceleration issues

Clean your exhaust. If you didn’t get the baffle out, you cleaned nothing. If it’s stuck, it’s because it’s plugged up and locked in place with oil/carbon build up. You must clean the baffle. That’s the part that gets plugged up!

Re: 1975 Puch Maxi rebuilt but has very low speed/acceleration issues

Thanks Seth!

I took the exhaust apart tonight and managed to get the baffle unstuck. It was pretty gunky but managed to clean it up good and put everything back together on the moped.

Unfortunately this hasn't fixed my issue though.

Re: 1975 Puch Maxi rebuilt but has very low speed/acceleration issues

> Seth B Wrote:

> -------------------------------------------------------

> Clean your exhaust. If you didn’t get the baffle out, you cleaned

> nothing. If it’s stuck, it’s because it’s plugged up and locked in place

> with oil/carbon build up. You must clean the baffle. That’s the part

> that gets plugged up!

So the baffle is all the stuff left in the main pipe after you take out the header and header pipe? It didn't look like that came out on mine. If that's the case, how do you break it free. I assumed it was welded in, and I ran about 4 cans of brake cleaner through at every angle I could manage. Got a lot of stuff out, but taking it apart would be optimal.

Re: 1975 Puch Maxi rebuilt but has very low speed/acceleration issues

clean points again, n retorque head bolts.

Re: 1975 Puch Maxi rebuilt but has very low speed/acceleration issues

> Lee Snover Wrote:

> -------------------------------------------------------

> > Seth B Wrote:

>

> > -------------------------------------------------------

>

> > Clean your exhaust. If you didn’t get the baffle out, you cleaned

>

> > nothing. If it’s stuck, it’s because it’s plugged up and locked in

> place

>

> > with oil/carbon build up. You must clean the baffle. That’s the part

>

> > that gets plugged up!

>

> So the baffle is all the stuff left in the main pipe after you take out

> the header and header pipe? It didn't look like that came out on mine.

> If that's the case, how do you break it free. I assumed it was welded

> in, and I ran about 4 cans of brake cleaner through at every angle I

> could manage. Got a lot of stuff out, but taking it apart would be

> optimal.

Yes, The baffle is in the tail section. There’s a nut in the center holding it in. Once the nut is removed, the baffle can come out, but they are often stuck. To get it unstuck, I heat the exhaust up with a torch and then spray the inside down with oven cleaner, and let it sit a few minutes. That has always worked for me.

Re: 1975 Puch Maxi rebuilt but has very low speed/acceleration issues

get yourself a can of ether(starting fluid) and spray it over every gasket and seam(intake, head)...if it stops running you have an air leak...go get a timing light at the Goodwill too.

I test for strong spark in a completely fucked up way...grab the plug n turn er over...if it hurts like hell and you would never do it again. Your spark is great!!! I have had many bikes with spark that just felt like a tingling...don't do this...

Re: 1975 Puch Maxi rebuilt but has very low speed/acceleration issues

Thanks for the tips guys!

I installed new points and re-configured the ignition timing and the bike now has spark again (a wire was a bit loose as well), engine sounds much better, and it will idle and goes pretty fast! Very happy with the results.

Definitely had a timing issue where the points were opening at the incorrect time.

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