piston melting

[grunt]

this my second piston this has happened to

it melts at exhaust port side and little bit breaks off then i loose my top piston ring into 3 bits and it goes into the exhaust and it doesnt score damage the barrel

why the hell is this ;D

temp gauge runs at half way all the time and nice ammount of smoke out the back

however i run a br9iex iridum sparky could this be the problem

regards grunt

[looey]

Oh mate, has this just happened after your rebuild ??.

Were you running it in when it happened or where you giving it beans ?.

[carlos]

What's the plug colour like?

What pistons are you using?

[grunt]

well i had done 200 miles running in and didnt exactly go grannys on it haha

its odd as i have had this similar problem before

oh well its only a piston i suppose however wow she shifts now i done them bits to it

carlos plug colour light brown as should be

all i can say is i think i gonna do the full 500 miles runnning in now (boring)

[grunt]

what do i i need to do if it is running lean is it in with the air screw or out forgot its been a while

[carlos]

If it's running lean at full throttle it's going to be main jet size!

[looey]

I would've thought it must be getting too hot or running too lean to be melting the piston at all anywhere ?.

The thing is, wherever it melts, it always ends up around the exhaust port area cos that's where everything goes obviously

Is the crown of the piston still ok ?, got any pics you can put up ?.

[grunt]

its the bit right infront of the arrow on the piston about 5-6mm wide little chunk comes off in one bit everything else is spot on a,,ok

[carlos]

There's no way it could be firing a tiny bit late is there?

[looey]

Apr 21, 2010 21:29:36 GMT 1 grunt said:

its the bit right infront of the arrow on the piston about 5-6mm wide little chunk comes off in one bit everything else is spot on a,,ok

Is it ported at all ?, sounds to me like it might be catching on the exhaust port to be breaking a bit off there ?.

[grunt]

im currently running a 240 in my rd125lc carbby with a leader kit fitted

[carlos]

post a pic up!

[grunt]

cant as its outside and im inside ;D ;D stressed with it atm so best i leave it for time being

[grunt]

spoke to a friend i gonna put a bigger pilot jet in to improve pull away and i am going to go from 240 to 250 ditch k&n and go with my foam one

then run it in as i get my new gen piston tomorrow and i be back out also i going to turn oil pump up slightly and put a little cap full of 2 stroke in tank like gaz does

[looey]

I'm fairly sure it won't be anything to do with oil quantity, cos if they run light on 2-stroke oil you would get heat seize pinches around the piston, normally in the 4 hot spots, you wouldn't get bits of the piston melting and breaking off through lack of oil ?.

[grunt]

well oild pump is currently running standard and i have filed ports smooth and got rid of rough edges boyseen dual stage reeds head skimmed 0.5mm iridium sparkplug leader kit and foam filter with micron so i think i should turn it up abit as standard amount of oil wouldnt do engine much good with these mods

gonna get a 25 pilot jet or near there instead of the 20 and might keep 240 main and tinker air screw abit ;D

[carlos]

They should have a bit of a shampfer on the ports I think

[grunt]

it does still have them there but from the rebore it had afew rought bits so my engine worker said file them away and 1200 wet and dry so completely smooth then it stands no chance of getting caught

[grunt]

sorted it today foam filter back on twist of air screw abit and plug was spot on ,,,removed head and looked and is all good now all thats left is to run it in

[rd50084matt]

Dont run extra oil in tank as it leans the mixture out more,common mis-conception that it helps,it doesnt.

Like Gaz said cooler plug on a tuned motor helps,9 instead of 8.

Good luck with it.

[grunt]

been out for the last 4 days lots of miles done runs like a dream and wipped head off and looked at piston and its sorted no melting nice colour ;D

[tobster]

glad you've got it sorted. sounds like it was running lean - now you've changed to a more restrictve (but better) air filter it has richened up. Can't see the pilot jet having any positive effect on your problem - more to do with part throttle running. Just to confirm all is better, do a WOT plug chop and have a real good look into the plug and not just the surface of it. White is lean = bad. Whenever you start changing the way air gets into a 2 stroke (e.g airbox mods, filter changes) you should always be checking the mixture. As said before, do not add extra oil to the fuel as it run even leaner. Premix OR oil pump, not both.

[grunt]

i ditched the oil in tank idea and have just finished running it in plug is great runs as sweet as a nut ;D ;D

some clown offered a swap for my 125lc for a minature hedgehog pet ;D