Advice needed: ZA50 kit piston skirt hits the crank case at btdc

puch malossi 62cc piston skirt is hitting the four triangular spots in the crank case I circled at bdtc. Should the cases or the piston get dremeled to clear? Why are those triangles in there anyway?

za50pistonskirt.jpg

Edited 1 time(s). Last edit at 03/31/15 10:25AM by airend.

Re: Advice needed: ZA50 kit piston skirt hits the crank case at btdc

Adam Klags MPG /

you should be capable of trimming of the skirt, whats important is transfers and exhaust opening in reference to the piston, and a final squish of the headEdited 1 time(s). Last edit at 03/31/15 10:44AM by nkotb.

Re: Advice needed: ZA50 kit piston skirt hits the crank case at btdc

i had the same problem i turned down the piston skirt a bit had no problems with doing that

Re: Advice needed: ZA50 kit piston skirt hits the crank case at btdc

Your sure its not the nub in the center?

Re: Advice needed: ZA50 kit piston skirt hits the crank case at btdc

Piston is super tall and bumps into the triangles in there. I'm sure the nub too. Someone recommend to remove the nub altogether.

Re: Advice needed: ZA50 kit piston skirt hits the crank case at btdc

It's actually hitting the nub in the center as alot of them do....

Re: Advice needed: ZA50 kit piston skirt hits the crank case at btdc

cut that piston skirt son.

Re: Advice needed: ZA50 kit piston skirt hits the crank case at btdc

Garrett Bell /

Reviving this thread,

Just got the malossi kit for my ZA50 and the skirt hits as well just the way the picture above shows. Was curious what the best way to trim the skirt would be?

I dont have any major machining equipment, was thinking maybe a chop saw with metal bit, or sanding on a flat surface or anything that MA can help brainstorm.

Attached are some pics of the piston, was also curious after the skirt is trimmed, do i need to modify the edges that are trimmed to mimic the angle inside the piston?

Any help is greatly appreciated, thanks!

Re: Advice needed: ZA50 kit piston skirt hits the crank case at btdc

sand the piston skirt edges on a belt sander to clear the obstacles in the cases. I used the Dremel tool and ceramic/tile bit. In the end I removed slightly uneven amount of material off piston skirt due to eyeballing everything, but it didn't matter and piston cleared.

Re: Advice needed: ZA50 kit piston skirt hits the crank case at btdc

Baron Von Hamilton /

I would use a dremel. I would measure mark and cut off what was hitting. I would also make sure all the ports open up. You may need to trim more.... IDK for sure I am not familiar with this kit.

Re: Advice needed: ZA50 kit piston skirt hits the crank case at btdc

Garrett Bell /

Thanks! i compared it to a stock piston and seems to be about 2mm ishhhh to clear so i'll try those techniques and report back

Re: Advice needed: ZA50 kit piston skirt hits the crank case at btdc

i use a 1950's belt sander that we call grinder-saurus.

Re: Advice needed: ZA50 kit piston skirt hits the crank case at btdc

DrGeorgeTompson (Alan) /

Just curious, why are you guys removing material from the piston instead of removing the material from the case? I would personally do the latter. That piston is comically long though.

Re: Advice needed: ZA50 kit piston skirt hits the crank case at btdc

Probably because nobody wants to split a za50 just to grind down those little spots. It's not a big deal if you're doing the bearings and seals at the same time though, but you know sometimes you're lazy and you want to see how much thirty year old crank seals can take.

Re: Advice needed: ZA50 kit piston skirt hits the crank case at btdc

the nub!

some had a nub in there specifically so you couldn't swap on the better cylinders to restricted bikes

some of the later ones even went so far as to have a hole through the nub so if you did grind it off you'd have a bonus leak hole.

I think most aftermarket cylinders adapted by having the piston skirt short enough or cutout divot to avoid the nub

but if it doesn't no reason you couldn't shorten the skirt or put in cutouts for those corners and the nub...

also no reason you couldn't file down whatever it's hitting in the case. as long's your not making holes anywhre it'll totally work

Re: Advice needed: ZA50 kit piston skirt hits the crank case at btdc

Baron Von Hamilton /

> Daniel '' Wrote:

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

> i use a 1950's belt sander that we call grinder-saurus.

This sounds rad

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