What would cause this piston damage.. twice.

Wesley Ambrosini /

I've had this happen to 2 treats 50cc top ends on the same ZA50, one after the other. The damage is identical, if I didn't toss the first damaged top end I would show pics. So wierd. I blew the crank out with air in case something got all up in that shizz.

Where do I go from here?

Re: What would cause this piston damage.. twice.

thats just one small nugget of shit that would do that. ya gotta do a full rebuild and keep it clean or wait for the tick tick kaboom

Re: What would cause this piston damage.. twice.

Captain Janeway /

In the top transfer is that an edge sticking in the cylinder?

Re: What would cause this piston damage.. twice.

Wesley Ambrosini /

> Captain Janeway Wrote:

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

> In the top transfer is that an edge sticking in the cylinder?

That's just damage from whatever it sucked up

Full rebuild it is.

Re: What would cause this piston damage.. twice.

Wesley Ambrosini /

Any way the shit that is continually getting into my cylinder is coming from the pipe? I had it welded back together and didn't clean it out or anything

Re: What would cause this piston damage.. twice.

> Wesley Ambrosini Wrote:

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

> Any way the shit that is continually getting into my cylinder is coming

> from the pipe? I had it welded back together and didn't clean it out or

> anything

Now might be a good time to get that done .

Re: What would cause this piston damage.. twice.

Lets CSI this shit - piston caught something on the top edge of the transfer and it gouged down the side of the piston. twice. all we know for sure is that there was (or maybe still is) something in three that caught and gouged. is there any shit still wedged in there to indicate what it came from?

size and shape matches pretty closely with a needle, how's the crank condition. I had a bigend bearing explode on a ZA once. nightmare status. Also circlips - are they all still there?

circlips and bearings are likeliest to catch on the transfers like that. stll anything getting in the cylinder is going to have a chance to catch on the transfers. Weld shit can screw you, it's possible to suck shit back up from the exhaust but still... not very likely.

Anthing missing from your carb>? I dropped out a throttle slide retaining pin from a clone bing once. never used a clone bing since...

Re: What would cause this piston damage.. twice.

Wesley Ambrosini /

> Born to be WillD Wrote:

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

> Lets CSI this shit - piston caught something on the top edge of the

> transfer and it gouged down the side of the piston. twice. all we know

> for sure is that there was (or maybe still is) something in three that

> caught and gouged. is there any shit still wedged in there to indicate

> what it came from?

>

> size and shape matches pretty closely with a needle, how's the crank

> condition. I had a bigend bearing explode on a ZA once. nightmare

> status. Also circlips - are they all still there?

>

> circlips and bearings are likeliest to catch on the transfers like that.

> stll anything getting in the cylinder is going to have a chance to catch

> on the transfers. Weld shit can screw you, it's possible to suck shit

> back up from the exhaust but still... not very likely.

>

> Anthing missing from your carb>? I dropped out a throttle slide

> retaining pin from a clone bing once. never used a clone bing since...

Carb is good to go.

Piston was intact the ring was still on, seized but still there. Circlips were still there. Nothing was in the cylinder the only evidence was the damage.

I'm thought the bottom end bearing went to shit because the con rod was a little chunky after the first cylinder destruction. I put a little pb blaster on it and it was smooth as butter (maybe not the best idea). The exhaust doesn't have anything rattling around. My brother welded a new stinger on it for me because the original was fucked.

The wierd thing is that everything is good to go after I put a new kit on it. I get a few miles out of it, start to tune, look at pipes on treats, then boom, engine peters out and I walk my ass home.

I'm pretty hesitant about cracking the case just because if I'm in there I'm going to do the bearings and seals. I know I can shim the crank but it's going to be a pain in the ass.

Re: What would cause this piston damage.. twice.

I bet it's the con rod big end bearing.

Re: What would cause this piston damage.. twice.

Wesley Ambrosini /

> Stephen Simmons Wrote:

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

> I bet it's the con rod big end bearing.

Ding ding ding

IMG_20190427_132430677.jpg

Re: What would cause this piston damage.. twice.

Damn, no wonder you had a problem how did the Bic get in there?

Re: What would cause this piston damage.. twice.

> Born to be WillD Wrote:

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

>I had a bigend bearing explode on a ZA once. nightmare

> status.

massive understatement.

my bet is chunks of bearing/bearing cage

Re: What would cause this piston damage.. twice.

Wesley Ambrosini /

Crank is a mess. You can see the big end bearing is falling apart. Going to get a top con rod pressed in locally. Ordering more bearings and seals right meow. Thanks guys. I shouldn't be a lazy mofo and just did a full rebuild right off the bat.

Re: What would cause this piston damage.. twice.

brutal. I feel your pain. best of luck

Also, I had mopedcrankworks do two for me with Rito conrods, roller bearing on the smallend too, definitely helps with higher RPM. And only like 75 bucks, which is less than the bearings and seals will run ya. though I usually just gear up on a ZA and let the transmission take care of lowend and keep rpm lower up top.

Re: What would cause this piston damage.. twice.

Wesley Ambrosini /

> Born to be WillD Wrote:

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

> brutal. I feel your pain. best of luck

>

> Also, I had mopedcrankworks do two for me with Rito conrods, roller

> bearing on the smallend too, definitely helps with higher RPM. And only

> like 75 bucks, which is less than the bearings and seals will run ya.

> though I usually just gear up on a ZA and let the transmission take care

> of lowend and keep rpm lower up top.

I have a 20t front sprocket to do just that. My local guy is working with my crank right now, I've heard mixed reviews on the Rito, but I think thats what I'm going to get pressed in.

Silver lining is that with a sturdier crank I can (someday) slap a bigger kit on it and rip.

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