a hole in the top of my piston!!!

lee's anus is leefungchowOG /

just blew a hole through the crown of my peugeot polini kit. great. detonation? yes? why? i think timing. what else can blow a huge hole in the crown??

suck.

Re: a hole in the top of my piston!!!

🇮🇹💦 Of the Loin /

too advanced timing

too high compression/too low octane fuel/too hot sparkplug

Re: a hole in the top of my piston!!!

does it look anything like this peugeot piston we fried last week?

that was from epoxy failing which closed holes in the cases that were opened really far. air leak air leak decomp boom.

a hole in the top of my piston!!!

Pre-det! Throw a bolt in the hole and run it until it really blows up. Seriously, I ran a scooter top end for about 500 miles with a bolt in the crown of my piston. WOOOOO

Re: a hole in the top of my piston!!!

we TIG'd it up and its good as new btw.

Re: a hole in the top of my piston!!!

lee's anus is leefungchowOG /

i was using a stock peugeot head and 91 octane.

mine likes like it has a Bigger hole and in the centre.

Re: a hole in the top of my piston!!!

Brendan Chenelle /

Is it inline with the plug?

Could be a sparkplug with too high of a heat range

Re: a hole in the top of my piston!!!

🇮🇹💦 Of the Loin /

check for air leaks, retard the timing a little bit

whats your compression? even with 91 and a b8hs on my moby the underside of the piston crown had a small burnt spot and i swear it was gonna blow through any day

Re: a hole in the top of my piston!!!

Timing, compression, fuel/air ratio, head design. A better head with a squish band could do the trick, but also retard the timing, put a thicker base gasket on, upjet.

By the way, I only have one peugeot head that I like, it's a doppler head with a nice squish band, but no hole for decompression!

Re: a hole in the top of my piston!!!

Wiat, did you seize, or just put a hole in your piston? Cause, if you didn't seize it, do what Brennan and peter said.

Re: a hole in the top of my piston!!!

metal everywhere!!!!!!!!!!!!!!!! fucked up my bottom end too.

Re: a hole in the top of my piston!!!

Dan Webber Kastner /

Here are some pics.

Re: a hole in the top of my piston!!!

it looks like it is going fast still. lol.

Re: a hole in the top of my piston!!!

ouch looks like my honda 450 piston. detonation 4 sure. yeah timing me thinks was off or slipped.

i had a mild detonation on my moby dopper 50 kit, the spark plug had melted and looked like someone had soldered on it. It wasn't as bad tho the cylinder has some nickel scrapped off onto the piston and I managed to remove the ring intact as well after a few hours of heating and picking/sanding.

Later i checked the timing low and behold it was way advanced. It must have slipped when i used a power drill to start it after it had sit for a month post flock yeah (no decomp on dopper). maybe I neglected to tighten it down hard enough last it was opened.

Re: a hole in the top of my piston!!!

that seized kit looks JUST like my polini 51 kit. same marks.

Re: a hole in the top of my piston!!!

lee's anus is leefungchowOG /

gay

Re: a hole in the top of my piston!!!

I like that it was rode hard. When I holed my Gilardoni pistoni I had no sieze look to it. Had you siezed it before?

Re: a hole in the top of my piston!!!

nope. that was it. it was PERFECT before.

how the hell did you not sieze??? there was metal EVERYWHERE!!!!! in my transfers, in my bearings, in my intake....

gayness

Re: a hole in the top of my piston!!!

Well I had sanded the piston down to a .005" fit with the cylinder out of frustration with previos siezing. Maybe that saved the sides of the piston but the crown hole was caved in around the edges indicating a melting heat. Maybe it heated up fast enough to hole the crown before heat moved to the skirt

Re: a hole in the top of my piston!!!

Oh I had metal in the case but when the crown caved in the engine stopped running immediately w/o compresiion

Re: a hole in the top of my piston!!!

on a peugeot the clutch will not un-engage at high speeds, this forced the metal into and through the engine everywhere.

Re: a hole in the top of my piston!!!

carumba

Re: a hole in the top of my piston!!!

Wow!!

Re: a hole in the top of my piston!!!

I think thats fairly standard on centrifugal clutch isn't it?

Re: a hole in the top of my piston!!!

Looks like predetonation directly under the sparkplug. Man... that's one nasty hole! It looks kind of like someone drove the spark plug through the piston with a sledge hammer.

Re: a hole in the top of my piston!!!

yeah, but when a piston soft seizes it is usually enough to stop the clutch at high speeds and it will let go, but on a french bike, there is a separate starter centrifugal clutch which is controlled by the spinning of the wheel. so when it seized, the piston Wanted to stop moving, but the rear wheel forced it to keep moving. gay.

Re: a hole in the top of my piston!!!

the one consolation of seizing on a french bike is that you get to do a kickass tailslide before going "fuuuuuuuuuck..............."

Re: a hole in the top of my piston!!!

I wouldn't' know, I haven't done that yet, but now I will, cause I just said that, so never mind.....or is it too late now? Fuck, I'm going to seize. But probably not. Blowing up cranks is my specialty.

Re: a hole in the top of my piston!!!

Look what I did to my new set up. Le FUCK!

Re: a hole in the top of my piston!!!

Someone started doing that to there piston in town. Jetting and timing I think, I have never had that problem on any my Peugeot's so far.

Want to post in this forum? We'd love to have you join the discussion, but first:

Login or Create Account