fitz18 Posted October 26, 2008 Author Report Share Posted October 26, 2008 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. Ive no timing advanced. Didnt notice any metal flakes on the plugs but they are a brown/black colour. I will take pics.Should I chop them to look down into them? The head has had no work done to it and shows no signs of damage. Im not sure what the compression was at before she blew. I checked with a local builder who is well respected in racing circles over here and he was the one who said 240mains were fine. He actually gave them to me as I had 220's in her. The cylinders were perfectly round as I had them measured before I got my wisecos. Thanks for the input. Quote Link to comment Share on other sites More sharing options...
fitz18 Posted October 26, 2008 Author 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. Nope there are no dings in the exhaust port. From all the replies I need to bump the main WAY up and mix 32:1. Correct? From D-Roc's post my pistons looked pretty good I thought??? Keep the replies coming guys. The help is much appreciated. Quote Link to comment Share on other sites More sharing options...
fitz18 Posted October 27, 2008 Author Report Share Posted October 27, 2008 Any one got good pics of pistons that have been subject to lean jetting?? Quote Link to comment Share on other sites More sharing options...
D-Roc Posted October 28, 2008 Report Share Posted October 28, 2008 your jetting looks fine IMO and if your plugs are brownish tan and dry then that confirms you jetted close. if you where too lean and were running WOT your pistons will melt. if you had too much timing or not enough octane, you would have deto holes in the pistons, if you did not have enough oil you would sieze. how does it run? does it run clean and rev up crisp or does it hesitate and fall on its face when you stab the throttle? IF your lean you should be feel a lean hesitation before the power kicks in. Quote Link to comment Share on other sites More sharing options...
Screaming Yellow Zonker Posted October 28, 2008 Report Share Posted October 28, 2008 WOW that sucks... have you checked the crank and rod bearings to see if they binding??? I was running 380-400 jets in my stroker with no porting. I would rather run rich and ride home than run lean and burn a piston or crank. Quote Link to comment Share on other sites More sharing options...
fitz18 Posted October 28, 2008 Author Report Share Posted October 28, 2008 your jetting looks fine IMO and if your plugs are brownish tan and dry then that confirms you jetted close. if you where too lean and were running WOT your pistons will melt. if you had too much timing or not enough octane, you would have deto holes in the pistons, if you did not have enough oil you would sieze. how does it run? does it run clean and rev up crisp or does it hesitate and fall on its face when you stab the throttle? IF your lean you should be feel a lean hesitation before the power kicks in. I was WOT when shee blew! Ive no timing advance. The bike ran well but some times bogged a little and need high revs to clear her out. I dont know what to think now. I guess ill just build her up and try bigger mains to get her jetted properly! Thaanks for the input. Quote Link to comment Share on other sites More sharing options...
fitz18 Posted October 28, 2008 Author Report Share Posted October 28, 2008 Also I was riding the bike for 6 months before shee blew up. If I was lean wpould the damage not happen earlier?? Getting frustrated with this. Wish I had a definate answer as to what happened so it doesnt happen again! Quote Link to comment Share on other sites More sharing options...
D-Roc Posted October 28, 2008 Report Share Posted October 28, 2008 (edited) we leaned a buddies quad out once and blew it the first time out. i would go with what your engine builder recommended. edit: 6 months of hard riding can wear stuff out. maybe it was a bad rod from the factory. There is no 100% true answer. Motors blow, sometimes sooner then later, that is why we have tools. lol. There is a guy with a superjet motor that had a rod let loose and it cracked the bottom and top case, cylinder, intake manifold, carb base, exhaust manifold and the head. Motor was complete junk, nothing worth saving. now that sux! Edited October 28, 2008 by D-Roc Quote Link to comment Share on other sites More sharing options...
fitz18 Posted October 29, 2008 Author Report Share Posted October 29, 2008 we leaned a buddies quad out once and blew it the first time out. i would go with what your engine builder recommended. edit: 6 months of hard riding can wear stuff out. maybe it was a bad rod from the factory. There is no 100% true answer. Motors blow, sometimes sooner then later, that is why we have tools. lol. There is a guy with a superjet motor that had a rod let loose and it cracked the bottom and top case, cylinder, intake manifold, carb base, exhaust manifold and the head. Motor was complete junk, nothing worth saving. now that sux! Thanks for the input guys. My engine is pretty much scrap as well. Just saving the clutch out of it BUt it wil be like a new bike when im finished so I want to get her jetted correctly. Quote Link to comment Share on other sites More sharing options...
Tim Potteiger Posted October 29, 2008 Report Share Posted October 29, 2008 240 is too lean for stock carbs with aftermarket pipes. I am not familiar with Aliens, but if they are anything like FMF or Toomey, then you need to be at least 280+ on the main. With stock needles, you might even need over 300. Quote Link to comment Share on other sites More sharing options...
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