88 kit blew up

[dum_as01]

88 kit blew up dont know why???

hey guys just thought id get your opinons on this one please...

Bought a secondhand storm 88 kit last week came with everything expect for the cam... also bought a new fmf pipe(sound wicked) put it in one night after work was all good running pretty good i thought, there was a little bit of a knocking sound when it was under load but other than that it was running sweet... took it out on sunday riding all was going good for about an hour then it just stopped took it home washed it took the head of and all these shavings fell out luckly only the piston is destroyed getting a new one tomoz i think... im not real sure why it happened though??? would running the sotck cam do these??? becuase that is the only thing that is different to when me mate had it???

thanks in advance for any answers you have!!!

ill post a picture of the piston if thats any help to you...

 

[foolsp33d]

there was a little bit of a knocking sound when it was under load

ouch........ lol

 

[Flarry]

Hmm the edge of the piston is broken, looks like it was hitting or scraping somthing and creating the shards you saw?? Dont know...

 

[daniel40]

what are the impressions on the top of the piston, mine had some small impressions and i had bent an exhaust port valve which could be the tapping sound you heard, but yours could be different.

 

[Mack]

Looks and sounds like detonation, which will keep destroying pistons if you don't do something to stop it. That knocking you heard is a tell tale sign.
Check your compression ratio to see what you have got.

 

[dum_as01]

Looks and sounds like detonation, which will keep destroying pistons if you don't do something to stop it. That knocking you heard is a tell tale sign.
Check your compression ratio to see what you have got.

yer thats wat me old man reckoned maby running lean??? i only used the stock cam would that matter??? how do i check the compression ratio???

 

[cass38a]

Check your compression with a compression tester.

 

[dum_as01]

Check your compression with a compression tester.

ok when i get a new piston and put back together ill do that... what should the compression be???

 

[AusJames]

If it's "knocking" or "pinging" under load, it's detonating. Could be ignition too advanced. could be too low octane rating for the compression ratio of the engine. If it's 9.5:1 or more I'd say you're going to need 95octane if not 98 octane. If it's a 12-13:1 then DEFINITELY need 98octane

but I'd check out the igntion before hand otherwse you'll just keep destroying engines

 

[Cactus Jack]

Yes , definitely looks like detonation damage . For the youngsters on here - detonation is when the fuel/air charge EXPLODES in the cylinder like a hand grenade and smashes the piston like a sledge hammer blow . It's caused by too low octane fuel to suit the compression ratio or too lean a mixture and can still happen even though the timing is at stock settings . When the mixture ratio is set just right - the fuel/air charge burns smoothly at a controlled rate - heating the air and making it expand rapidly to push the piston down and drive the crank without damaging anything .

Pre ignition from glowing carbon or sharp metal edges , too high a compression ratio , or too much ignition advance , starts the fuel/air burning and expanding BEFORE the piston has reached top dead center - so the piston has to withstand the force of having to compress the expanding charge which is actually trying to drive it backwards down the cylinder in the opposite direction . It puts a massive load on everything - the piston , the pin , the rod , the crank and the cases .

So if you feel your engine pinging , hestating or jerking ~ STOP IT , GET YA' BUTT OFF THE BIKE , AND TAKE IT HOME to retune it !!!!!! Or face the costly consequences !

 

[Ruby]

^^^ All of the above.

Detonation.

By 88 kit you mean you bumped the capacity from 50cc to 88cc? So you punched out the capacity over 65% but did nothing to increase the fueling = detonation city. If thats correct, then that was just plain silly now wasn't it?

The markings at the base of the piston means you might also want to check out the bore. And what are those notched at the base of the piston under the pin?

 

[dum_as01]

By 88 kit you mean you bumped the capacity from 50cc to 88cc? So you punched out the capacity over 65% but did nothing to increase the fueling = detonation city. If thats correct, then that was just plain silly now wasn't it?

The markings at the base of the piston means you might also want to check out the bore. And what are those notched at the base of the piston under the pin?

i put a 88cc kit on which came with a 20mm carby, pod filter, high flow oil pump, heavyduty clutch springs and i put a new fmf pipe on... as for the bore it is fine not a mark on it the as for those notches at the base of the piston they were already there before i put it on. im still waiting for a new piston but i think i might rejet the carb maby lower the compression a bit and get out the timing gun and check the timing properly just hope it dosnt happen again.

 

[Mack]

Yes running a stock cam with high compression kit is whats wrong I'd say. High comp piston and race cam are designed to go together. The long inlet duration of the race cam will lower your dynamic compression ratio to where it should be. A lot of people run into problems slowly building their engine up (usually due to finance issues) but really once you embark on the performance path it is a complete system you are building. Each thing depending on another to work right.