drz FCR 39mm with cone filter /no airboot

[fullytwisted]

Hi All,   just testing the water.......Any one have any experience with jetting a FCR 39mm on a drz 400 stock motor with no air boot ?  it has a uni filter right off the carb.  it runs good now , just wondering if i could ,should fatten the main jet up one size or lean it out one  size just to get the most out of it.. it already has a full yoshi with a 39 mm with the o-ring mod?.   Thanks in advance .. BBrrRRaaPPPPP!!!!

[William1]

It will run better with an OEM airboot and airbox. Not doubt you would need to significantly larger jets than those that do the recommended 3"X3" hole in the stock airbox due to a weaker vacuum signal you will get at the carb. A windy day is going to affect your jetting as will your leg placement if that changes the air flow turbulence.

[Beta300REcat]

Ran a UNI stand alone on my CR125 and it ran just fine. The Screaming Eagle air system for the Harley also eliminated any type of box and it too runs just fine. Best way to jet your carb is to start rich, lean it until it protests, then go back one step richer.

[fullytwisted]

Anyone have any experience with this ? ..I have a stock motor 2013 drz400sm with a 39 mm carburetor .. also has a full Yoshimura exhaust ..recently I took the air boot off and put on a single uni air filter everything runs great just wondering if I could go up in the main jet or possibly down in the main jet to get the best out of the carburetor. Thanks

[fullytwisted]

I think the jetting is close . I was just wondering if anyone had done this to the DRZ400 and what set up they had in their carburetor or if they changed it at all I played with the air mixture screw which seemed to work a little bit

[William1]

Fuel screw is for idle only. You set for a nice, smooth idle and that is it. Needle, length, diameter and taper are for about idle, main is mostly WOT and the slow air jet tapers the slow speed circuit and the main air jet helps raising fuel up through the needle jet.