1978 Puch Maxi Luxe

Kevin Boughton /

Hey guys, I recently bought a 1978 Puch Maxi Luxe Hi-Torque that didn't start. I had to replace the plug, cylinder, piston, the stock head was still ok to use, carburetor, and petcock. All were replaced with stock replacements from treatland. Air filter is stock.

I just got it to start, but when I do, it just accelerates until I hit the kill switch. It's on the kickstand so it doesn't move, but the RPMs are don't stop going up until I stop it. Usually, I'd keep it running while trying to tune it but I don't want to run it at all right now because of the new cylinder, even for a few seconds to look at it.

The throttle cables havent been changed but they don't seem to be stuck in the open position or anything. The carburetor was bolted on right from treatland because I just wanted to get it started before anything else. I'm going to clean it tonight, try again, and let you know how it goes. Figured the float might be stuck?

Any insight that will save me some time would be greatly appreciated.

Thanks,

KB

Re: 1978 Puch Maxi Luxe

This is definitely a pretty big airleak. Air is entering from somewhere other than the carb inlet. This is analogous to having another carb somewhere (without any gas) with the throttle fully open which leads to the continuous acceleration you're seeing. Your bike will not idle, run super lean, and possibly blow up if you ride it like this.

Make sure all your gaskets aren't leaking and are tight (intake, base, case, etc). If they're fine you probably need a rebuild as one of your seals has failed.

Re: 1978 Puch Maxi Luxe

Kevin Boughton /

Full ☭ Now Wrote:

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> This is definitely a pretty big airleak. Air is

> entering from somewhere other than the carb inlet.

> This is analogous to having another carb somewhere

> (without any gas) with the throttle fully open

> which leads to the continuous acceleration you're

> seeing. Your bike will not idle, run super lean,

> and possibly blow up if you ride it like this.

>

> Make sure all your gaskets aren't leaking and are

> tight (intake, base, case, etc). If they're fine

> you probably need a rebuild as one of your seals

> has failed.

Thanks for the tip and you're probably right. I forgot to add in the last post that during the process of trying to start it, I took the air filter off. After it got started, I covered the intake with my hand and it seemed to level off somewhat. I was given 2 gaskets for the carb/intake side of the cylinder but only installed 1 when I swapped the cylinder and piston. While the carb is off, I'll take the intake off and put the 2nd gasket in.

I'll start there and let you know how it goes.

Re: 1978 Puch Maxi Luxe

It should be ok with only one gasket, just make sure that both metal surfaces are clean and flat. Also be sure to tighten the bolts evenly so that it doesn't end up being tightened down cockeyed.

If there were no airleak, covering the intake with your hand would kill the bike immediately.

Re: 1978 Puch Maxi Luxe

Kevin Boughton /

Full ☭ Now Wrote:

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> It should be ok with only one gasket, just make

> sure that both metal surfaces are clean and flat.

> Also be sure to tighten the bolts evenly so that

> it doesn't end up being tightened down cockeyed.

>

> If there were no airleak, covering the intake with

> your hand would kill the bike immediately.

I found the problem by spraying carb cleaner on the different joints. When I bought the new carb, I realized the original throttle cable fitting on the top of the cover wasn't the same as the new carb. In order to save time, I ended up using the bottom of the new carb with the top of the old carb. The problem was that I forgot to take the gasket from the new carb's top and put it in the existing one on the bike. Still needs some fine tuning but definitely not running nearly as high anymore.

Re: 1978 Puch Maxi Luxe

Kevin Boughton /

Another update...

While looking at the old carb, I checked the jet number. The stock one is a "66" while the new carb is an "82". I changed the 82 for the old 66 and things definitely run better.

I have no idea if all of the new carbs come with an 82, but I figured I'd share this in case someone is looking at buying the Bing Clone Carb on treatland.

Re: 1978 Puch Maxi Luxe

When you buy a new carb the suppler has no idea what jet you will need. Good move to swap old one .

Re: 1978 Puch Maxi Luxe

Overpriced Parts /

Stock was never a 66 jet. Someone put the wrong jet in .

And you should be in the 70s range for a 15mm bing unless your pipe is all blocked up.

Google jetting

Re: 1978 Puch Maxi Luxe

Kevin Boughton /

Ken Roff Wrote:

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> Stock was never a 66 jet. Someone put the wrong

> jet in .

> And you should be in the 70s range for a 15mm bing

> unless your pipe is all blocked up.

> Google jetting

I'm not an expert and wouldn't be able to debate this. It's just what I found. Then last night I ended up stumbling on this: http://www.myronsmopeds.com/category/service/carburetor-service/puch-carburetor/

I have the 1/12/304 version of the carb (stamped on the side) which apparently comes with a 66.

Any tips on how to seal the intake side of the carb? It still idles high and when I do the carb cleaner spray trick, the carb/intake joint just doesn't seal up well. It seems to be the only leak though. Is there supposed to be a plastic washer or o-ring there? I was going to try the soda can gasket trick but wasn't sure if there was any easier way.

Re: 1978 Puch Maxi Luxe

Kevin Boughton /

Steve Clark Wrote:

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> When you buy a new carb the suppler has no idea

> what jet you will need. Good move to swap old one

> .

Yeah, not a big deal. It'd be nice if they told you what jet it came with though. Having to order/mail a little jet by itself after the fact seems silly.

Re: 1978 Puch Maxi Luxe

Go Myrons, not even bing list the 12/304: http://www.bingpower.de/en/service/tuning-manuals/

But yeah, the bing clone from treats, even the 12mm (assuming that's what You got) is hardly a 'stock replacement', you will have to jet accordingly, also the slide, needle, or atomizer could be different. You can always swap those over though. What was wrong with the original carb anyway? Long as nothing was stripped all one should ever need is a bowl gasket or float needle, maybe a float, nothing else really wears out..even then all you would need to replace is the body or bowl..

Find a 20mm OD x 1-2mm o-ring and slip it in the bing, then slip that on so the end of the intake squashes it a bit (you will have to to get it in to place), that will seal it up. Eventually the o-ring will squish flatter and stay in there so it's easier to install the carb.

GL

~M (edited)

Re: 1978 Puch Maxi Luxe

Also, unless they added it to the description since you ordered, they do list the jet it comes with...

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