2wheelturned4 Posted December 19, 2012 Report Share Posted December 19, 2012 After all my stuffing around with jets and electrical problems, turns out my 3 hour old top end has let go. It is an athena 392cc kit, so 67.95 athena pistons. the left one has broken the crown on the intake side, down to the top ring. there is no marks anywhere to indicate a snagged ring. Bike has 27.5 pilots, 340 mains, k&n airfilter with no lid, fmf sst's with powercore 2 silencers, needles are on the middle clip position. Bike seemed to be running slightly rich if anything, what could cause this to happen? Would it be possible that it was just a shit piston? It was only the second ride since the rebuild, any ideas at what might cause this? Quote Link to comment Share on other sites More sharing options...
ClayAiken Posted December 19, 2012 Report Share Posted December 19, 2012 A shitty piston would cause this. Nothing you did. Athena is shit. Quote Link to comment Share on other sites More sharing options...
sprinklerman Posted December 19, 2012 Report Share Posted December 19, 2012 A shitty piston would cause this. Nothing you did. Athena is shit. dont agree with this ^^^ because you NEED to identify what EXACTLY the problem was ,so as not to repeat it. Instead of just saying the piston was "crap" or Athena is "crap", and throwing a new piston in,,and then it happen again. Id call Cam at Redline as he has messed with several Athena kits if i remember correctly. Quote Link to comment Share on other sites More sharing options...
2wheelturned4 Posted December 20, 2012 Author Report Share Posted December 20, 2012 if a ring got caught there would be a tell tale sign correct? this thing doesnt have a mark anywhere, bike still ran but only on full throttle. I ran an athena piston in my Ktm 525 sx and didnt seem to have a problem though i only put maybe 2 hours on it before i sold it. could a bit of sand past the air filter cause anthing like this? i dont really trust the k&n in the sand, and have a proflow setup to change to once it is running again. Im thinking sand past the airfilter would more likely mark the bore though Quote Link to comment Share on other sites More sharing options...
#1JUANstunna Posted December 20, 2012 Report Share Posted December 20, 2012 Post pics of the damage. Quote Link to comment Share on other sites More sharing options...
Banshee Climber Posted December 20, 2012 Report Share Posted December 20, 2012 RDZ also works with these cylinders, or at least that's the info I have gathered from this site. Quote Link to comment Share on other sites More sharing options...
locogato11283 Posted December 20, 2012 Report Share Posted December 20, 2012 340 mains!? That's fucking huge. Jetting that is way too rich can cause overheating. Maybe you should look there. - HMFIC Quote Link to comment Share on other sites More sharing options...
bluebanshee98 Posted December 20, 2012 Report Share Posted December 20, 2012 like tyler said 340 mains is way to big on a stock stroke unported bike. if you have to run that big of mains in stock carbs then more then likely you have a bad air leak in your intake boots. i ran 340 mains in stock carbs on a 4 mil dune port bike with shearers Quote Link to comment Share on other sites More sharing options...
2wheelturned4 Posted December 20, 2012 Author Report Share Posted December 20, 2012 2 of my mates who are both on stock un-opened engines are running 320/330 mains, both have standard air boxes, one is running same pipes as me the other t6's, with my airbox having no lid shouldnt this be ok? i am at sea level in perth australia... even if it is a lil rich would that cause the crown to break? i will try to get some pics up over the weekend Quote Link to comment Share on other sites More sharing options...
Jereme6655 Posted December 20, 2012 Report Share Posted December 20, 2012 If it gets hot enough it can cause damage to the pistons at the crown on the exhaust side.....look at the other piston and see if it shows signs also.....look very close. Yes being over richly rich can kill motors. T6 pipes are for stock port motors. And say running t6 pipes and no lid I would THINK you should be somewhere in the realm of 280 for a main and possibly a 27.5 for a pilot jet..... Quote Link to comment Share on other sites More sharing options...
2wheelturned4 Posted December 20, 2012 Author Report Share Posted December 20, 2012 it was running a little on the hot side, but nothing like when it melted down. it was running 280s with 25 pilots before the athena top end went on, it always ran hot then and after really getting into it, it melted down in a big way after maybe half an hour. that took a similar size chunk out of the piston but was the exhaust side, not the intake side. plus there was a 5mm hole in it, where is now its just a broken crown. the right piston look ok, same colouring, no damage. the bike was good to start, wasnt smoky, just was sluggish on the bottom with a reasonably strong top end. what kind of signs would i be looking for if it was being too rich that caused this? Quote Link to comment Share on other sites More sharing options...
dirtydownunder Posted December 20, 2012 Report Share Posted December 20, 2012 what do the plugs look like, do they look the same as each other ? are you running stock ignition timing ? and theres no marks on the bore ? my 350 dune port, with t5's ran 330 main and 25 pilot in stock carbs. stock 350 with t5's was 280main. the 421 serval ran 340 main in stock carbs but was a bit rich. Quote Link to comment Share on other sites More sharing options...
2wheelturned4 Posted December 21, 2012 Author Report Share Posted December 21, 2012 both plugs are quite black,yeh it is stock ignition and no marks in the bore. all the hone marks are still visible. Dirtydownunder, you might know him, Grummer from Grummer racing did my mates 04 with the 330's and the t5's.i spoke to him before going up to the 340's, and i also spoke to perth quad parts who suggested the same thing. My mates 07 running the same pipes only has vents added into his airbox and it was tuned by south coast motorcycles in esperance when he first got it, its running 320's and 25 pilots, his bike is by far the best running stocker i have been around, not sluggish on the bottom at all and is nearly as quick as mine was up top, 280's in mine were to lean, even before this topend went on. bike was overheating in no time and boiling its coolant out. Am i missing something really basic? I have had my carbys off heaps before this happend, could i have got an airleak or something? It has a k&n with outer sock and no lid on the box. Bike has been really shit off the bottom since iv had it, probly worse with the athena top end, but always had a good top end Quote Link to comment Share on other sites More sharing options...
2wheelturned4 Posted December 23, 2012 Author Report Share Posted December 23, 2012 both pistons are cracked through the skirts. left one is missing the whole bottom of one window, the left is just missing a small piece of the centre, but some cracks through from the centre of the piston. both bores are ok, no marks, nothing to indicate a snag. but the left is missing the intake side of the crown, down to the second ring. I will post some pics tonight, what am i missing with this? Quote Link to comment Share on other sites More sharing options...
dirtydownunder Posted December 23, 2012 Report Share Posted December 23, 2012 i know of the shop, but dont know much about them. its weird not to have any tell tale marks, when you go to rebuild, id deff get the crank checked out tho, trued and welded. with the overheating, have you checked the water pump impeller, radiator maybe blocked ?. running rich can cause overheating. does sound like youre rich, id play with jetting a bit. warm the bike up on old plugs and go for a bit of a thrash on new plugs, with out being off the throttle much. pull over and check out the plugs. they shouldnt get too dark straight away, a nice tan to lightish choc brown is good. when i was running 280 mains 25 pilots with t5's, the airbox lid was on, but the box had 12 1" holes in it, running pods or without lid would prolly jet close to around 310ish. my ported 350 ran 330's with t5's and that was jetted pretty dam perfect. was piston to bore clearance checked out ? Quote Link to comment Share on other sites More sharing options...
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