Wildcardracing Posted October 25, 2008 Report Share Posted October 25, 2008 I agree that sounds lean but I also agree the damage doesn't really jive with a lean condition failure. Rod through the case, ouch :ermm: I'd like to see some pics... weakest link always goes first. you were way too lean. Quote Link to comment Share on other sites More sharing options...
AKheathen Posted October 25, 2008 Report Share Posted October 25, 2008 Ok guys so Ive blown up my engine and am trying to figure out why. Here's my set up: 2001 shee, dmc alien pipes, k&N filter in box snorkle removed, 240mains, stock pilot, air screw 1 1/2 turns out, 40:1 mix mild ported cylinders i bought of firehead on here I started stripping down the bike and noticed the keeper screw and clamp that tightens agianst the left hand carb cap (stock carbs) is missing. would that have an effect on it? O some info: wen i say blown up the pistons are intact but the left crack rod came out through the case. Did alot of damage. Have got new crank, new cylinders, new pistons, and while im at it im sticking in a new trans. Bike ran great before blew up although sometimes it would bog under low revs. Any icdes. Thanks Gerard first off, you should be running 32:1 mix. second, what entails the mild porting? it,s probably just a port polish w/out any reshaping involved, which reduces atomization that should occur from turbulence before it reaches the crank case. think of it as a partial distilling process which allows the fuel to remain suspended for combustion leaving the oil to lubricate and cool the rotating assembily evenly. limiting this process will cause the fuel/oil mixture to have mor innertia and only cool lubricate and atomize of the first piece of hot metal it touches, which would mostly be the pistons (top and bottom) and the crank weights. larger jetts and a 32:1 mixture would have probably saved your motor. then again if there is scooring on the intake side, too much was taken off durring the porting and caused the pistons to cock and drag. Quote Link to comment Share on other sites More sharing options...
fast500#12 Posted October 25, 2008 Report Share Posted October 25, 2008 your oil to gas ratio will effect jetting but you can run at 50 to 1 with no problems as long as your premix oil can support it. i know some people that run 100 to 1. i personaly have run 45 to 1 for years with no problems, it all depends on the oil you use. you are deffinatley lean on you jetting. with mild porting the same pipes as you and k&n filters i was running 300 main jets and 27.5 pilots at 4500ft of elevation. if you can post some pics of your pistons and rods i could probably give you a better idea of what really happened. throwing a rod usually isn't caused by a lean condition, there was more than likely some other issue that caused that. take pictures of the tops sides and bottom of the piston dome, if it got hot there will be carbon under the piston above the wrist pin. and of corse the rods an crank. Quote Link to comment Share on other sites More sharing options...
fitz18 Posted October 25, 2008 Author Report Share Posted October 25, 2008 Here's the pics guys. http://i326.photobucket.com/albums/k402/ge.../Banshee009.jpg BOTH PISTONS http://i326.photobucket.com/albums/k402/ge.../Banshee007.jpg PISTON & ROD http://i326.photobucket.com/albums/k402/ge.../Banshee002.jpg CASE DAMAGE http://i326.photobucket.com/albums/k402/ge.../Banshee005.jpg CYLINDER WALL Also just to let you's know I was running on reserve when the bike blew up and the piston and cylinder wall still had oil on them when I took the piston out of it. THanks for all the replies guys. GREAT SITE :biggrin: Quote Link to comment Share on other sites More sharing options...
fitz18 Posted October 25, 2008 Author Report Share Posted October 25, 2008 Do you's think them pistons look like a lean condition? Quote Link to comment Share on other sites More sharing options...
fast500#12 Posted October 25, 2008 Report Share Posted October 25, 2008 Do you's think them pistons look like a lean condition? yeah you were lean. the lean state makes the top of the piston hot and when the fuel mixture comes in the cylinder it causes lots of carbon on the top ofthe piston. the opposite is true if you are rich you get piston wash, the fuel washes the carbon off the top of the piston. perfect jetting will leave a 1/2 inch diameter chocolate brown light carbon circle right below the spark plug hole. Quote Link to comment Share on other sites More sharing options...
D-Roc Posted October 26, 2008 Report Share Posted October 26, 2008 In my limited experience a lean WOT run tends to melt the top of the piston from the added heat. This happens on the exhaust side of the piston crown and melts down usually to the rings until you loose compression. on our jetskis when we swamp our skis and fill the motor with water it is important to get the water out and the motor up and running ASAP so you can burn out the moisture. If you don't, then next time out your rods usually let go. ask me how i know. IMO an airleak doesn't throw rods but stranger things have happend. Quote Link to comment Share on other sites More sharing options...
dirtfreak Posted October 26, 2008 Report Share Posted October 26, 2008 what oil have you been using,what spark plugs was your running/heat range also what did your spark plus look like.i would like to see some pic,s of your spark plugs.no doubt about running rich.but about running 32:1 mix i dont know? ive been running 40:1 for over 2 years on the same top end and still running strong so far and i ride allot more than most guys on here,i live in the country ride almost every day.where your rod is broke off near the piston to me would seem like a excessive heat while over reving issue.hard to tell from the pics. Quote Link to comment Share on other sites More sharing options...
fitz18 Posted October 26, 2008 Author Report Share Posted October 26, 2008 what oil have you been using,what spark plugs was your running/heat range also what did your spark plus look like.i would like to see some pic,s of your spark plugs.no doubt about running rich.but about running 32:1 mix i dont know? ive been running 40:1 for over 2 years on the same top end and still running strong so far and i ride allot more than most guys on here,i live in the country ride almost every day.where your rod is broke off near the piston to me would seem like a excessive heat while over reving issue.hard to tell from the pics. So you reakon I was rich?? Did you mean lean?? I was using castrol A747 race oil. Im not sure about the heat range of the plugs but they are one that the local bike shop gave me. I was WOT when the damage was done. Quote Link to comment Share on other sites More sharing options...
fitz18 Posted October 26, 2008 Author Report Share Posted October 26, 2008 In my limited experience a lean WOT run tends to melt the top of the piston from the added heat. This happens on the exhaust side of the piston crown and melts down usually to the rings until you loose compression. on our jetskis when we swamp our skis and fill the motor with water it is important to get the water out and the motor up and running ASAP so you can burn out the moisture. If you don't, then next time out your rods usually let go. ask me how i know. IMO an airleak doesn't throw rods but stranger things have happend. From that pic attached my pistons look about right then do they not? Quote Link to comment Share on other sites More sharing options...
dirtfreak Posted October 26, 2008 Report Share Posted October 26, 2008 So you reakon I was rich?? Did you mean lean?? I was using castrol A747 race oil. Im not sure about the heat range of the plugs but they are one that the local bike shop gave me. I was WOT when the damage was done. yea i meant lean don't know why i said rich,im getting up there in age and having brain farts more often i guess.i was wondering the heat range of the plugs you was running cause everyone wants a hot plug but when you start advancing timing and doing port work etc you want a colder plug and a higher octane fuel.i couldn't really tell much from your pic's need pic,s with more angles of the pistons and the other parts.the pistons do look like they were running lean though from what i could tell.did you have any metal flakes on your plugs.what color where your plugs when you pulled them.also did you have anything done to your head like milling or rechambering.how much compression did your motor have prior to exploding.im running 340 mains on stock carbs so i would say you was running lean 4 sure.when you bought your ported cylinders you didnt do any research on jetting?on you rod that broke i have seen b4 rods breaking from a crooked cylinder bore.i had a buddy that broke 2 rods until he figured out that he had a crooked bore from someone we both know that don't bore our cylinders anymore. Quote Link to comment Share on other sites More sharing options...
AKheathen Posted October 26, 2008 Report Share Posted October 26, 2008 Here's the pics guys. http://i326.photobucket.com/albums/k402/ge.../Banshee009.jpg BOTH PISTONS http://i326.photobucket.com/albums/k402/ge.../Banshee007.jpg PISTON & ROD http://i326.photobucket.com/albums/k402/ge.../Banshee002.jpg CASE DAMAGE http://i326.photobucket.com/albums/k402/ge.../Banshee005.jpg CYLINDER WALL Also just to let you's know I was running on reserve when the bike blew up and the piston and cylinder wall still had oil on them when I took the piston out of it. THanks for all the replies guys. GREAT SITE :biggrin: all i can say is that it looks like that piston got a little hot around the wristpin. as for the 32:1, i am assuming that ireland is as humid as alaska, if not more, except for the dry winters. everyone cranks the oil back up for summer or switch to a hotter plug for winter. Quote Link to comment Share on other sites More sharing options...
AKheathen Posted October 26, 2008 Report Share Posted October 26, 2008 all i can say is that it looks like that piston got a little hot around the wristpin. as for the 32:1, i am assuming that ireland is as humid as alaska, if not more, except for the dry winters. everyone cranks the oil back up for summer or switch to a hotter plug for winter. p.s. send your new pistons to swaintech coatings fr a ceramic and friction coating. it doesn't cost much. Quote Link to comment Share on other sites More sharing options...
fast500#12 Posted October 26, 2008 Report Share Posted October 26, 2008 i was looking at the second pic again and noticed the piston skirt on the exhaust side is broken. it may have broken after the rod snapped, but it could have broken and caused the rod to snap. are the any chunks out of, or dings in the exhaust port on that cylinder. Quote Link to comment Share on other sites More sharing options...
fitz18 Posted October 26, 2008 Author Report Share Posted October 26, 2008 first off, you should be running 32:1 mix. second, what entails the mild porting? it,s probably just a port polish w/out any reshaping involved, which reduces atomization that should occur from turbulence before it reaches the crank case. think of it as a partial distilling process which allows the fuel to remain suspended for combustion leaving the oil to lubricate and cool the rotating assembily evenly. limiting this process will cause the fuel/oil mixture to have mor innertia and only cool lubricate and atomize of the first piece of hot metal it touches, which would mostly be the pistons (top and bottom) and the crank weights. larger jetts and a 32:1 mixture would have probably saved your motor. then again if there is scooring on the intake side, too much was taken off durring the porting and caused the pistons to cock and drag. Ok from the replies I think il change my mix to 32:1. The mild porting does include some reshaping of the intake ports. Thats really it. Quote Link to comment Share on other sites More sharing options...
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