Guys, was recently "debating" with a mate who was adamant that a Hi Flow Petcock was required with a stage 1 upgrade (EVO). He reckoned that with an air filter and an S&S E carb if you didnt run a new petcock it would starve for fuel.( No cam, no headwork etc, stock motor) I told him to lay off the crack pipe. My logic was that he was suggesting that the flow rate of the standard petcock was so borderline as to be redundant with the minimal additional fuel requirement that a hi flow filter and rejet would require. He was equally adamant that the SS carb made a huge increase in his bikes performance, where as I was telling him that for next to nothing a few simple mods to the stock CV 40 would have yielded identical results.

Question, should it be me laying down the pipe?

Not sure who is right but I was running my 1998 evo with the following engine mods on the standard harley fuel tap and never had any problems:

SE 1340 EVO heads
Se Valve springs

1st oversize rebore / SE 10.5:1 pistons 

SE SE-57 camshaft

SE 44 carbie and air kit

Dyno results were in the low 90's HP so if it was staving for fuel I would be surprised.

Hi Houndog, a lot of people beleave that a high flow petcock needed when you start looking for more power.

one reason is that when your wide open throtle, the stock vacume shut off valve can partly close the petcock as vacume decreases.

i road & raced my 01 twin cam dyna for about 7 years with stock Petcock no problem, i did a best speed of 120 mph  and best ET standing quarter 11.2 with stock petcock 95cubic inch.

i saw that a mate that races a 05 lowrider 114 cubic inch screamin eagle carb model. still has stock petcock on he has ran 11.0 1/4 mile and fast speeds, i just took the guts out of the diaphram so its not a vacume shut off, i had to manuely shut off ( can't leave on all the time ) i now have a Pringel high flow a sponsor gave me, not much different in the speeds i do. i think if your bike is starving for fuel you would feel it.

cheers

When I bought my bike it already had S/E pipes and a 45 slowjet...I have just  just upgraded the air filter and rejetted the standard carby and there is a noticable increaase in power and it doesn't starve for fuel with the standard tap...

Just fitted an E series with high flow filter to mine also done the cams and exhaust left the standard petcock and there is no problems with the engine getting enough fuel.