skinak Posted June 1, 2012 Report Share Posted June 1, 2012 So I put a .035 shaved head on my shee with stock pistions and a dune port. I started out with 330 mains and 30 pilots and it was running super lean. Then worked my way up to 370 mains and 35 started turning a nice brown, then made a few more passes and came to a screaching stop. got home from the dunes and pulled it apart and found that I broke the crap out of the bottom of the pistons. What the went wrong? The plugs were looking great the all the sudden nothing. I had BR8ES plugs. any words of advice? Thanks Nick Quote Link to comment Share on other sites More sharing options...
spurdy Posted June 1, 2012 Report Share Posted June 1, 2012 So I put a .035 shaved head on my shee with stock pistions and a dune port. I started out with 330 mains and 30 pilots and it was running super lean. Then worked my way up to 370 mains and 35 started turning a nice brown, then made a few more passes and came to a screaching stop. got home from the dunes and pulled it apart and found that I broke the crap out of the bottom of the pistons. What the went wrong? The plugs were looking great the all the sudden nothing. I had BR8ES plugs. any words of advice? Thanks Nick How was the piston broken? Intake side, exhaust side? Bottom under the crown? I'd guess most likely too large of a piston clearance and you broke the skirt. SP Quote Link to comment Share on other sites More sharing options...
Zwiser Posted June 1, 2012 Report Share Posted June 1, 2012 Your powerband must have bent and hit the piston skirts. its quite common once you go over 100 mph Quote Link to comment Share on other sites More sharing options...
erickson483 Posted June 1, 2012 Report Share Posted June 1, 2012 Did you ever do a squish test? Compression test? Leakdown test? All of these should be done before you start running a new bike or new rebuild. Quote Link to comment Share on other sites More sharing options...
spurdy Posted June 1, 2012 Report Share Posted June 1, 2012 Did you ever do a squish test? Compression test? Leakdown test? All of these should be done before you start running a new bike or new rebuild. He never said it was a new bike or fresh rebuild. Only the he changed the head. At which point he should have checked the squish. SP Quote Link to comment Share on other sites More sharing options...
erickson483 Posted June 1, 2012 Report Share Posted June 1, 2012 A bad air leak would help explain the huge main jet and still being lean. Quote Link to comment Share on other sites More sharing options...
BigRed350x Posted June 1, 2012 Report Share Posted June 1, 2012 If the skirts broke off it was probably excessive piston to cylinder-wall clearance or you had some detonation issues and the pistons couldn't handle it and broke. Quote Link to comment Share on other sites More sharing options...
vulvafan537240 Posted June 1, 2012 Report Share Posted June 1, 2012 35 pilot sounds huge. Are these stock carbs? Quote Link to comment Share on other sites More sharing options...
locogato11283 Posted June 1, 2012 Report Share Posted June 1, 2012 Must have been an air leak somewhere. Those are huge jets. Quote Link to comment Share on other sites More sharing options...
skinak Posted June 1, 2012 Author Report Share Posted June 1, 2012 these are stock carbs, I don't think I have an air leak cause I had 310 mains before head change and I was running rich. I haven't touched the internals minus getting the cylinders ported, since I was a moron and bought it new in 05. I went from 30 to 35 pilots because that is all the local shops had. Quote Link to comment Share on other sites More sharing options...
skinak Posted June 1, 2012 Author Report Share Posted June 1, 2012 only the left piston is damaged.. intake side is broke from the middle of the windows down and about the same height on the exhaust skirt.. exhaust side has got a v pattern where it broke at Quote Link to comment Share on other sites More sharing options...
erickson483 Posted June 1, 2012 Report Share Posted June 1, 2012 Can you post pics? Quote Link to comment Share on other sites More sharing options...
skinak Posted June 1, 2012 Author Report Share Posted June 1, 2012 here are the pics Quote Link to comment Share on other sites More sharing options...
vulvafan537240 Posted June 1, 2012 Report Share Posted June 1, 2012 I do a leakdown test anytime I mess with the head. 27.5 is all you should need on the pilots. 30 was probably too big and 35 is way too big. Quote Link to comment Share on other sites More sharing options...
Jereme6655 Posted June 1, 2012 Report Share Posted June 1, 2012 correct me if im wrong here guys.....but i was pretty sure you didn't have to rejet when you change out for more compression. I get that its always good to ceck your jetting whenever you cange something.....even if its just to make sure..... however to go up 6 sizes on mains and to go up 2 on the pilot.....makes me think there was an air leak. Quote Link to comment Share on other sites More sharing options...
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