Puch maxi stock piston size is under 49mm?

Hi all, its been a while since I've posted, bike still isn't running but I recently the will to try at it again.

I was told it was making a bad sound before it died because the new piston I installed was too long and was slamming into the spark plug. So I measured the new, too long piston and the old stock one I had replaced. Looking for replacements on treats it seems that a stock piston should be 49mm from the bottom to top not including the crown. Sure enough, my newer piston is actually around 51mm, too long (checked the page for the product and it said 49mm so I suppose mine just wasn't perfect.

But here's the issue - I measured my old piston and its 47mm in length, not 49.

So im probably just going to order the 49mm now and try it out since I dont see 47mm pistons on treats. If the next one I order is once again too long, could I just dremel it down a bit?

Would appreciate any thoughts, thanks!!

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Re: Puch maxi stock piston size is under 49mm?

It's also important to measure from the center of the wristpin to the crown

Re: Puch maxi stock piston size is under 49mm?

What spark plug are you running? Needs to be ngk b7hs or similar. If you are running a b7es it's too long and that will cause your problem. If you are running a random off brand plug ditch it and get the right one.

Re: Puch maxi stock piston size is under 49mm?

Aidan Schmidt /

It seems I somehow lost my spark plug, so not sure. Guess I'll order a new one - would this be the correct plug?

https://www.amazon.com/dp/B01DMFHO2G/

New piston arrived and it's 49mm as advertised. Wrist pin distance seems good. As you can see in this pic though the piston in its entirety is longer than the original (47mm), is that going to be an issue?

Going to remove the flywheel for the first time now in order to replace the points, wish me luck!

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Re: Puch maxi stock piston size is under 49mm?

Aidan Schmidt /

Update: I think I successfully replaced the points! Once I get the piston and spark plug figured out and try to star it, if I still don't have spark, well there's just another thing I potentially messed up lol.

Hopefully not, I think it went pretty smooth despite it being the first time I removed the flywheel.

Re: Puch maxi stock piston size is under 49mm?

I'd go with a B6HS, its one heat range hotter than B7HS. You can pick them up locally at your auto parts store. Give them the stock number, (7534) for B6HS, (5110) for B7HS.

I'm not sure your "short" piston is actually OEM puch, that rough machining looks more like what you would find on a modern aftermarket part.

Re: Puch maxi stock piston size is under 49mm?

Ngk now sells pre-gapped plugs. You could Order exactly whacha need online.

Re: Puch maxi stock piston size is under 49mm?

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don*t throw away that 47mm piston

the piston skirt length effects port timing on the intake side

its a hot-rod piston

get new rings for it and set it aside

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