Puch Maxi: engine cuts out at mid RPMs

Basically, all the symptoms of a bad pickup or ignition coil. Bike revs fine up to nearly 1/2 throttle. Then it hits a notable level and cuts out and sputters pretty hard. This happens either on the stand or while riding. When riding, I can feather it to about 30mph on a thinline before cutting out and hard sputtering if I go over the line. The cutting is hard, which makes me think electrical. However, the lights do not flicker when it’s cutting out.

I’ve seen this before: changed ignition coil and back to rippage. Not so this time. What I’ve done (essentially replaced every electrical part on the bike):

~~ NOTE: stator is Treats CDI~~

- upgraded pickup coil to motobecane version

- upgraded ignition coil to motobecane version

- Replaced the 2041 Pietcard Box with new

- Replaced external coil with pietcard version

- Replaced plug wire and boot on ext coil

- Varied spark plug gaps

- Checked and quick cleaned carb

After replacing all these parts, I still get the issue so I hooked up to a timing light. Everything starts out normal. I see my line auto advancing, as it is supposed to do initially, then when I reach a certain RPMs (about half 1/2 throttle), the line just completely vanishes and the cutting out begins! I’ve read some people talk about their fire mark jumping a complete 180 degrees but I haven’t confirmed that in my case since that would put the fire mark underneath the flywheel and I’m all solo with no help.

I have not tried adjusting the timing yet as I see no real reason it could have gone from just fine to all fucked up in a moment. Any ideas, insight, personal experience would be greatly appreciated. I just can’t fathom wtf could be the problem here. I’m convinced it’s electrical; but I’m open to your thoughts.

Thanks guise! (If I haven’t already, I’ll try to come back and add a YouTube link)

Re: Puch Maxi: engine cuts out at mid RPMs

Sounds like a bad connection or ground somewhere thats reacting to vibration. Most likely somewhere or something you have not touched yet with all the replacements you have made. Might have a look at kill switch for instance.

Re: Puch Maxi: engine cuts out at mid RPMs

> live ɘvil Wrote:

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

> Sounds like a bad connection or ground somewhere thats reacting to

> vibration. Most likely somewhere or something you have not touched yet

> with all the replacements you have made. Might have a look at kill

> switch for instance.

Good call and good advice. I’ll give it a once over today since I’m off work and get back. I thought this could be the case too but since I took apart so much wire and my main ground, I figured idda touched the problem.

But my custom killswitch toggle makes a prime suspect. Fingers crossed. And thanks.

Re: Puch Maxi: engine cuts out at mid RPMs

> live ɘvil Wrote:

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

> Sounds like a bad connection or ground somewhere thats reacting to

> vibration. Most likely somewhere or something you have not touched yet

> with all the replacements you have made. Might have a look at kill

> switch for instance.

So I took a look and found one of the screws to the killswitch not tightened down on the wire. I was able to pull the wire completely free.

What do you think? Possible culprit? Gonna take it apart and try to get her right.

CDC0F0D2-E3B9-4F8D-AB37-00914F9B4754.jpeg

Re: Puch Maxi: engine cuts out at mid RPMs

Love the wire nuts.

Not sure how those will do over time with vibration though.

I bought a whole strip of wire connector block from an electric contractors supply house in Louisville. Walked in they had the correct size in stock. Bought a strip long enough to rewire 3 or 4 mopeds for like 5-6$. Was white instead of black but who cares?

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Re: Puch Maxi: engine cuts out at mid RPMs

Nice. Yeah I think that’s the next step for me too. I’ve used the wire nuts on another bike that hasn’t had any issues in 3 years but this bike is enough of a headache that using a strip makes sense and it’s easy.

So I tried my best to get in that space and screw the wire back in. That didn’t seem to do the trick so I’m gonna cut that switch off and replace it with another one.

Re: Puch Maxi: engine cuts out at mid RPMs

If you can't track anything down with the wiring, then consider checking fuel flow is sufficient for high rpms. In other words the fuel flow from tank to carb may be enough to idle and run to half throttle but not enough beyond.

Which reminds me to remind you to check gas cap vent operation. Simple test would be to remove cap all together while testing.(edited)

Re: Puch Maxi: engine cuts out at mid RPMs

I’ve considered both these things. The issue just suddenly started out of the blue while out on a ride after about a half season of solid rippage. so I’d be interested to know how due flow issues might change so suddenly. I actually just checked to see if the fuel filter was draining too quickly and with just a quick rip of the throttle, the cutting out happens. Not even giving fuel time to deplete significantly.

But when you’re out of options, it never hurts to try different things. I’ll try the gas cap truck then after that I’ll completely disassemble and reassemble the carb in case there’s a blockage.

Also, note in the video that the headlights don’t flicker when the cutting out begins. Would they cut out if it were an electrical issue or would the fact that lights are a different circuit make it not matter?

And fuel flow issues wouldn’t explain the odd behavior of my fire mark when using a timing light, would it?

Re: Puch Maxi: engine cuts out at mid RPMs

Get a bottle of injector cleaner from the dollar store and dump a 1/3 - 1/2 bottle into a full tank of gas . Run that through while riding mostly hard . Repeat .

I had some build up from the crap gas we get these days and that^ cleaned things nicely .

Re: Puch Maxi: engine cuts out at mid RPMs

Re: Puch Maxi: engine cuts out at mid RPMs

Replace spark plug and see if that does better...

Re: Puch Maxi: engine cuts out at mid RPMs

Check your needle and jet. Clean them all out. If you block some of the intake will it rev. up. normally.

My 78 Puch stopped running right as soon as I put a new air cleaner on. Am running a 56 Jet. It runs great with the old clogged up air cleaner. Sputters out with the new free breathing filter. So I'm pretty sure I need to upjet to get things back in balance. These are both stock air cleaners, so I was quite surprised.

Re: Puch Maxi: engine cuts out at mid RPMs

> Lee Snover Wrote:

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

> Check your needle and jet. Clean them all out. If you block some of

> the intake will it rev. up. normally.

I haven’t made it to the carb yet to try this. I just really feel it’s electrical by the way it cuts out. But I will give this a try (covering the intake) after I wire in a new killswitch and clean the carb.

Re: Puch Maxi: engine cuts out at mid RPMs

sounds like an air leak.

If you have carb clean let the bike run and spray carb cleaner on your gaskets and seals.

If the motor cuts out...wala you found the leak

Re: Puch Maxi: engine cuts out at mid RPMs

> K Olena Wrote:

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

> sounds like an air leak.

>

> If you have carb clean let the bike run and spray carb cleaner on your

> gaskets and seals.

>

> If the motor cuts out...wala you found the leak

It’s not an air leak, I assure you. In 4 years I’ve never built a bike that developed an air leak at surface mating. It’s a fairly new build as well so it’s doubly impossible. I still need to reword that killswitch to find out if that was the issue.

Re: Puch Maxi: engine cuts out at mid RPMs

LOL, those statements can bite you in the hind end. Worth checking at least.

Whenever I'm sure I didn't do something, it usually when I did something. ;-)

Hope you can get to the bottom of it. Did you check the carb and clean it. It really sounds like you are not getting enough fuel. If it ran fine previously, I'm betting there is some crud blocking fuel flow in the carb.(edited)

Re: Puch Maxi: engine cuts out at mid RPMs

> Lee Snover Wrote:

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

> LOL, those statements can bite you in the hind end. Worth checking at

> least.

>

> Whenever I'm sure I didn't do something, it usually when I did

> something. ;-)

>

> Hope you can get to the bottom of it.

Lol. You’re definitely right about that! I’m actually gonna make sure I check it now.

Re: Puch Maxi: engine cuts out at mid RPMs

Yeah, it’s not the killswitch. Took it apart to the same symptoms. I’m considering changing the entire stator. Re wiring after that!

I just don’t understand.

Can a voltage regulator go bad? It’s about the only electrical part I haven’t replaced.

Re: Puch Maxi: engine cuts out at mid RPMs

voltage regulator will only effect your lights

Re: Puch Maxi: engine cuts out at mid RPMs

have you tried to run fuel from another container with no filter?

Re: Puch Maxi: engine cuts out at mid RPMs

I have not. But I have run a timing light and there is no spark when it cuts out at high rpm. Which leads me to believe it’s not fuel related?

Re: Puch Maxi: engine cuts out at mid RPMs

todd amundson /

It’s that Treats CDI. I actually signed on just to tell you that.

Powers in the points

Re: Puch Maxi: engine cuts out at mid RPMs

Thanks. Lol. I’m definitely suspicious of it. I’m gonna replace it with either points or the hpi.

Thanks for the reassurance that I’m not going bananas.

Re: Puch Maxi: engine cuts out at mid RPMs

DrGeorgeTompson (Alan) /

https://www.mopedarmy.com/forums/read.php?6,4171132,4171638,flat=1#msg-4171638

Here's a thread i made a while back. It's literally the exact same problem. It's a different stator, and bike all together but the operation conditions are the same. but that treats CDI is notoriously bad.

Check the exciter coil for shorts the wires on them are pretty thin and tend to get fucked. You will probably need to rewrap or just replace it.

actually, you replied to that thread at some point.(edited)

Re: Puch Maxi: engine cuts out at mid RPMs

DrGeorgeTompson (Alan) /

Oh i read the thread now lol and i see you replaced a lot of the bits. But it still seems like ignition charging issues. Maybe that moby coil isn't strong enough or the flywheel isn't. I don't think it's fuel personally, that stuff usually doesnt just stop working.

Re: Puch Maxi: engine cuts out at mid RPMs

Yeah, I don’t know man. It’s a head scratcher for sure. Like, it was running fine one second and the very next, BOOM!

It literally happened as I was riding it! Was zipping a long and then suddenly it started cutting out. Same symptoms no matter what I have replaced or rebuilt.

The only thing I haven’t done is played with the timing. But I don’t think at any point of bad timing is a symptom cutting out? Maybe, idk.

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