Piston Carnage - Need suggestions

Morris Edwards /

Oct 29, 2019 08:04AM

Bike - Derbi Senda DRD Xtreme 2012 50cc

Top end was a Naraku 50cc kit, seized it before due to an air leak, had a very slight gouge in the bore after honing, anyway new piston went in and the imperfection is the only explanation I can find for this happening (see photos)... Crank doesnt have any play.

Anyway my question is - will this cylinder head be reusable, it's not warped but has alot of scratches, if I just cleaned up the scratches and replaced the cylinder and piston surely itd run fine? Or what sort of effect would using this cylinder head have on performace/engine life.

Also some metal shavings/bits of the broken up piston ring seem to have gotten down onto/around the crank. Any suggestions of getting them out without splitting the cases? Was going to try my luck with compressed air and see where that gets me?

Re: Piston Carnage - Need suggestions

Dirty30 Dillon /

hydra

Oct 29, 2019 08:48AM

That top end is fucked, and it will not run.

The naraku kit is also the least expensive top end you can buy. Get a quality top end and properly tune your bike.

Re: Piston Carnage - Need suggestions

ken gilbert /

ride5000

Oct 29, 2019 10:09AM

to reinforce what dillon said, some of those gouges in the head look DEEP.

you don't want any sharp edges in the combustion chamber as they promote detonation, and you'd have to take off a LOT of metal to get those gouges smooth. i would call it a loss and start over with a fresh one.

re: failure analysis, when you rebored the old can, how did you do it? having just done a 0.4mm overbore on a chappy polini cylinder i can tell you the only way (outside of a machine shop) is with a rigid hone.

also, after honing, did you chamfer ALL of the ports well? that carnage looks like a ring got snagged, cracked in pieces, and ended up on a rampage.

Re: Piston Carnage - Need suggestions

Rebel Moby /

rebelmoby

Oct 29, 2019 10:11AM

Piston cylinder and head belong here...

Re: Piston Carnage - Need suggestions

live ɘvil /

themotorhead

Oct 29, 2019 10:43AM

All I can do is look away. Nasty

Re: Piston Carnage - Need suggestions

Captain Janeway /

avalon78676

Oct 29, 2019 01:46PM

Send that stuff to Rebel.

I'd open the case and clean it. There has to be crap all over it so why trash your new setup?

Re: Piston Carnage - Need suggestions

Captain Janeway /

avalon78676

Oct 29, 2019 01:48PM

Rebel,

lol! I have some pistons that should come to you

Re: Piston Carnage - Need suggestions

Potr zebie /

bullsachs101

Oct 29, 2019 01:50PM

did you drop a diamond in the chamber?

Re: Piston Carnage - Need suggestions

Chris Squid /

Go to branch

christopherc

Oct 30, 2019 02:29PM

Holy shit.

You’re going to have to split the cases, no way around it. Way too much metal flying around in there.

Re: Piston Carnage - Need suggestions

baird co /

bairdco

Oct 30, 2019 05:25PM

Instead of splitting the cases, hold it upside down over a trash can.

And then drop it in.

Re: Piston Carnage - Need suggestions

* * /

countryboy1

Oct 30, 2019 11:42PM

Wow dude it looks like the piston was hitting the head. You probably forgot a spacer or used the wrong gasket or the piston was longer then the og.

Look the that top ring groove! It’s Gone.

Yeah the top ring broke into a million pieces.

Re: Piston Carnage - Need suggestions

Dirty30 Dillon /

hydra

Oct 31, 2019 08:57AM

That whole motor should be gone through, there is no point wasting time and money trying to bandaid that when AM6 parts are readily accessible and knowledge so readily available.

Re: Piston Carnage - Need suggestions

Ryan Graeme /

bigrvg

Oct 31, 2019 10:54AM

That is knarly! Case split is the only way to prevent another situation like this.

Re: Piston Carnage - Need suggestions

Thomas Peffer /

thomaspeffer

Oct 31, 2019 07:57PM

Yeah that piston, head and cylinder are garbage now. Just chuck it and start over. That top ring must have shredded the whole insides when it broke apart. Look at those score marks. Deep as fuck. That piston/head/cylinder has seen it's last rpms

Re: Piston Carnage - Need suggestions

Josiah Radebaugh /

peug103

Nov 01, 2019 12:40PM

Pics of the cylinder?

Re: Piston Carnage - Need suggestions

Fred Braue /

Go to branch

fredb

Nov 01, 2019 03:48PM

yeh its totaled, am6 motor? i would change the crank also or have it rebuilt. personally since am6 parts are not so bad on costs unless you go nuts i would buy a crank/kit/seals and go over it. i think i have a stroker kit here as well as maybe a dozen or more new cylinders of multi brand

Re: Piston Carnage - Need suggestions

live ɘvil /

themotorhead

Nov 01, 2019 06:48PM

Find another stock running motor to slap in there for now.

Re: Piston Carnage - Need suggestions

cheetahchrome . /

cheetahchrome

Nov 02, 2019 12:34AM

Instead of splitting the cases, hold it upside down over a trash can.

And then drop it in.

Ha Ha BRAAAAAACCCCKK (edited)

Re: Piston Carnage - Need suggestions

Jack Rutherford /

churioz

Nov 02, 2019 09:37AM

> ken gilbert Wrote:

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

> to reinforce what dillon said, some of those gouges in the head look

> DEEP.

> re: failure analysis, when you rebored the old can, how did you do it?

> having just done a 0.4mm overbore on a chappy polini cylinder i can tell

> you the only way (outside of a machine shop) is with a rigid hone.

>

do you have a link to your rigid hone and how long did that take?

Re: Piston Carnage - Need suggestions

ᴛᴇʀʀʏ ᴅᴇᴀɴ /

Go to branch

dean

Nov 03, 2019 08:49AM

did you gap the rings on the new piston? this looks like classic didn't-gap-the-rings carnage to me

Re: Piston Carnage - Need suggestions

ken gilbert /

ride5000

Nov 04, 2019 06:43AM

> Jack Rutherford Wrote:

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

>

> do you have a link to your rigid hone and how long did that take?

Jack I grabbed mine off Amazon

Lisle 16000 Small Cylinder Hone

https://www.amazon.com/dp/B000P1802O/

only took about two hours and I was going slowly/ carefully. after a lot of research i kept the stones dry (no oil). honed from opposite ends alternately to prevent any taper.

Re: Piston Carnage - Need suggestions

G HANDS /

gray3339

Nov 04, 2019 12:48PM

This to me looks like several issues. Ring gap and spacing are two I can identify off hand. It's hard to tell because everything blew up but it appears from looking at the head that the piston was hitting it. Check the stroke on that kit. It probably needs a base spacer to be correct. It looks like you can see the round imprint of the piston on the head.

Anyway it's fucked, I would never run that bottom end again till I spilt the cases and cleaned it up. Why spend money on a iffy set up. Sucks, but you gotta do it right.

Re: Piston Carnage - Need suggestions

live ɘvil /

themotorhead

Nov 04, 2019 12:55PM

> G HANDS Wrote:

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

> This to me looks like several issues. Ring gap and spacing are two I can

> identify off hand. It's hard to tell because everything blew up but it

> appears from looking at the head that the piston was hitting it. Check

> the stroke on that kit. It probably needs a base spacer to be correct.

> It looks like you can see the round imprint of the piston on the head.

>

> Anyway it's fucked, I would never run that bottom end again till I spilt

> the cases and cleaned it up. Why spend money on a iffy set up. Sucks,

> but you gotta do it right.

I would ad that it looks like it was ran for some time after the initial failure.

Re: Piston Carnage - Need suggestions

G HANDS /

gray3339

Nov 04, 2019 01:07PM

I agree completely!!!

Re: Piston Carnage - Need suggestions

Dirty30 Dillon /

hydra

Nov 04, 2019 01:24PM

I don't think impact caused the failure, I think impact occurred after the initial failure.

Wouldn't be surprised to see the small end bearing missing a needle or two, which found it's way into the combustion chamber where it impacted the piston crown, rattled around and then found it's way lodged into the transfer. The resulting shrapnel could have done all that damage in a matter of seconds given the AM6 is happily revved out to 8-9K.

Re: Piston Carnage - Need suggestions

ᴛᴇʀʀʏ ᴅᴇᴀɴ /

Go to branch

dean

Nov 04, 2019 03:37PM

I still think it was ring gap issues. The ring expanded, got caught in the cylinder, broke the piston and then the bits o ring piston jackhammered the head, imo

but yeah, that's a full rebuild if you're doing it right

Re: Piston Carnage - Need suggestions

live ɘvil /

themotorhead

Nov 04, 2019 08:19PM

We have yer to see the cylinder. Pics please.

Re: Piston Carnage - Need suggestions

Jack Rutherford /

churioz

Nov 12, 2019 11:00AM

do you have a link to a cylinder bore gauge. I'm finding ones that only go down to 50mm.

> ken gilbert Wrote:

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

> > Jack Rutherford Wrote:

>

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

>

> >

>

> > do you have a link to your rigid hone and how long did that take?

>

> Jack I grabbed mine off Amazon

>

> Lisle 16000 Small Cylinder Hone

>

https://www.amazon.com/dp/B000P1802O/

>

> only took about two hours and I was going slowly/ carefully. after a lot

> of research i kept the stones dry (no oil). honed from opposite ends

> alternately to prevent any taper.

Re: Piston Carnage - Need suggestions

P D /

pdcomm

Nov 12, 2019 11:12AM

> Jack Rutherford Wrote:

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

> do you have a link to a cylinder bore gauge. I'm finding ones that only

> go down to 50mm.

15 bucks Harbor Freight :

https://www.harborfreight.com/6-piece-telescoping-gauge-set-5649.html

Re: Piston Carnage - Need suggestions

Jack Rutherford /

churioz

Nov 12, 2019 11:23AM

sweet and I like that price, thanks!

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