Two Puch Maxis won't idle

My wife and I each have a Puch Maxi, hers a '78, mine a '76. We got them last summer, and they ran great all season. When we got them back out again this year, they both began to develop the same problem: as soon as they warm up, they stall out when slowing down or stopped unless the throttle is held nearly half open. Besides this, they still run great. Both have 50cc kits and 12mm Bing carbs dilled out to about 14mm (I don't have an accurate way to measure exactly). Neither have expansion pipes. So far, I've done the following:

-Screwed the idle mix screw all the way in

-Changed spark plug

-Tried jet sizes 64, 66, 68, 70

-Tried the 2nd and 3rd needle clip settings

-Cleaned the carb

-Sealed an air leak where the intake pipe meets the carb

-Checked fuel flow from the petcock

I've searched through a bunch of the forum and couldn't quite find the same situation. If anyone has any suggestions, I'm at my wits end. If you need more info, let me know. Thanks!

Re: Two Puch Maxis won't idle

Downhill Harvey (OFMC) /

uh, I think your jet is way too small. Have you checked the tuning spreadsheet? I'm just guessing, but try a 74 &76 &78 jets.

Re: Two Puch Maxis won't idle

Downhill Harvey (OFMC) /

If it runs better with the choke partially closed, the jet is too small.

Re: Two Puch Maxis won't idle

compression timing or airleaks. probably airleaks if it's related to it warming up.

that or maybe fuel flow. try checking directly at the carb, like pull it off and hold it in your hand with the bowl off and see if gas flows steady. try pushing the float up by hand too and be sure it stops flowing properly.

Re: Two Puch Maxis won't idle

Overpriced Parts /

Timing before jetting.

Kits can't take hi stock timing you may have already damaged them.

Time with a light at 16-17 degrees on flywheeel with 16-18 thousands.

Bored carbs need the atomizer size for the size you bored them at. If not

You will never get them to run right.

14mm bings come with #222 atomizers

15mm bings come with #217 atomizers

If your "bored carbs" are between 14-15 then your kinda screwed.

If 14.5 mm then you need a hard to find #220 atomizer.

Me thinks you got a horrible #212A atomizer in your carbs.

#51slides suck too you need #24 slides

Stock exhaust needs stock carb, stock air box and stock air box

You made a missmatched set up for sure.

Kit needs a chamber pipe, hi flow filter, bigger jets, low timing

Re: Two Puch Maxis won't idle

If your "bored carbs" are between 14-15 then your kinda screwed.

This is nonsense.

So is this:

Stock exhaust needs stock carb, stock air box and stock air box

Re: Two Puch Maxis won't idle

Overpriced Parts /

U silly ^^ of course a seasoned tuner can tune anything a noob

can't so if stock stick to stock parts for correct jetting and idle.

In other words if you got a 2hp maxi and you run a 12mm bing with stock parts/58-60 jet, full air box and stock exhaust your bike will idle and run good but if you change to make more air in (bored carb) you have to make changes/ tuning to get correct air fuel mixture.

Many people on this forum have idle problems with bored carbs but if you have other sizes of atomizer/ slides/slide mods they can be tuned

Just slapping on a bored carb most case won't run right

Re: Two Puch Maxis won't idle

flush out tank put new gas in. also check banjo fitting, there is a small screen inside.

Re: Two Puch Maxis won't idle

Thanks everyone for the input. Let me first say I am indeed somewhat of a novice at this, though I'm picking it up. The setups we're running are the way that we bought them...I just haven't had the cash to replace the carbs or get better pipes. Ken, I was told the carbs should be close to 14...my wife's bike has a 222 atomizer, mine a 220. I'll have to check which slides we have. Of all the things you guys have given me to check, which would be most prudent to start with, keeping in mind that both bikes ran PERFECTLY for the first six months I owned them? It was only this season that they started acting up, which leads me to believe that the pipe and carb themselves, though not ideal, aren't the problem....

Re: Two Puch Maxis won't idle

Returning to the old problem...I didn't have much time for the last month to work on the bikes, but I finally went through a number of the suggestions I got on here the other day. I have not checked/done the following, and still no idle:

-Checked fuel flow both at the petcock and at the carb itself (took the bowl off and it flowed steadily - stopped when I pushed the float up)

-Tried all of the needle clip settings.

-Tried jets from 64-70. Seems to run best around 68 or 70 at WOT, but still won't idle. Would try higher if anyone thinks it would help, but I'd have to order them.

-Cleaned the carb thoroughly.

-Sealed a couple air leaks.

-Did the slide mod a few people recommended

-New Spark plug

-Checked compression

-Checked exhaust for blockages

After all this it still runs fine when moving, it just won't idle. When started, if I just let it sit there, it will run fine for about three minutes or so until it warms up, then it starts to struggle a little, and within a minute will stall. When riding it, if I keep the throttle open a bit at stop lights I can keep it running, but unless I do this also while braking, it will stall as it decelerates. Also, if I don't hold the throttle open enough and the idle gets too low, it takes forever to pick back up. I open the throttle all the way and it struggles for a few seconds before kicking back in. If anyone has any other ideas of what I could try, I'd greatly appreciate it!

Re: Two Puch Maxis won't idle

Overpriced Parts /

It's still a jetting problem

Your too rich at idle

Bored carbs are hard to tune

Put #217 atomizers in them then rejet

Re: Two Puch Maxis won't idle

I had the same issue, exactly. Turns out, when I'd put my carb back together after a cleaning and the metering needle clip, which I normally kept on the 2nd notch on the needle (default) had slipped all the way to the last notch.

I took the carb back apart, moved it back to the 2nd notch and it's been running like a champ ever since.

Re: Two Puch Maxis won't idle

I had the same issue, exactly. Turns out, when I'd put my carb back together after a cleaning and the metering needle clip, which I normally kept on the 2nd notch on the needle (default) had slipped all the way to the last notch.

I took the carb back apart, moved it back to the 2nd notch and it's been running like a champ ever since.

<tried to post this at the end of the thread here but for some reason it posted in the middle somewhere. I'm adding it again here where I intended it.>

Re: Two Puch Maxis won't idle

Jimbo Grand Daddy /

You must be using threaded view.

Re: Two Puch Maxis won't idle

Thanks folks, I'll try some of these things again. Ken, I may just be reversing things in my head, I am still rather new to this, but it seems to me that if the idle was too rich, giving it some throttle would kill it faster. As it is, if I keep the throttle open a bit, it stays running.

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