Motorcycle Repair: popping through the carb, vacuum hoses, lean mixture

Question
i have a 2005 XL1200C sportster with a popping through the carb..i took the bike to a local dealer to have the bike checked out..they called me back and told me it was valve guide seals..i got the bike back and it seemed to run ok....i just took the bike out today and it started to run the same way it did before i took it in for service.i mainley happens when it is warmed up..please help..getting discoureged.

Answer
First of all, if it's doing the exact same thing you should take it back to the dealer and give him a chance to fix it right for free.  Popping through the carb is a "lean miss" condition that is caused by a lean mixture OR an air leak somewhere.  If you have no air leaks at the intake manifold or the vacuum hoses and fittings on top of the carb, then the mixture is too lean.  It usually happens at low RPM when you just crack the throttle open or at low RPM in any gear.  The cure is to take off the bowl, carefully unscrew the low speed jet (should have a number on it like 43) and drill it out with a needle drill .020 size.  Then adjust the idle mixture screw (on the back underside of the carb beneath the silver plug) so it is about 2 1/4 turns out.  That always works for me.  It is such a common situation with Sportsters!!  I have never seen an '05 that needed valve guide seals to cure the problem.  The problem is that usually the dealers just back out the mixture screw 3 or 4 turns.  That won't cure the problem 100% because that screw controls air AND fuel together, and you need to increase the fuel without increasing the air to richen the low RPM mixture.  Good Luck.