Hey guys-
I'm in the process of rebuilding my Scrambler and am looking at getting a Keihin 39 PWK carb. I've heard that adding a pipe and porting hurts the gas mileage some, but will the larger carb hurt the mileage even more? Also, will the stock carb be adequate for the mods listed in my signature? Thanks.

 

I can't really help answer ur question but u should let me know how it all works out for you in the end and how you like it because I am looking into doing about exactly what you will be doing with your quad and just want to know how big of a difference it makes.

 

The stock carb will work fine but you will have to rejet. A bigger carb will definately kill gas milage. Bigger carb means more air and fuel.

 

Well, I can tell you already that the trail pipe makes a HUGE difference on the 400's. I put the pipe on my 95 Sport 400, rejetted, and took it for a quick ride. It didn't fit right, the jetting was probably off, and the clutching didn't allow the pipe to reach it's peak power, but it was still a night and day difference. The midrange hit of the pipe is amazing! I've heard adding porting to a piped 400 is like adding a pipe to a stock machine. I'll definitely keep an update on the progress of my machine.

I would probably be happy with just the trail pipe on my machine, but I want to make the Honda and Yamaha guys think their quads are slow.

 

Yes porting is the next biggest hp increase you can do. It is like doubling the hp gain from your pipe. A ported, piped and properly clutched 400 is very fast and not much stock will touch it.

 

A bigger carb will not change gas mileage, but jetting will.

 

A bigger carb will indeed affect gas mileage. The 39pwk is much bigger. Bigger carb means bigger jets= more fuel!

 

You're porting and adding a pipe to add power. THe is no comparision between the stock carb and the pwk carb. Much more power and throttle response with the pwk. Gotta decide want you really want, it will definatley use more fuel with the the porting. You'll need the full race mod setup if you want to have any chance making the new Honda and Yamaha guys looks slow!

 

Yes, the 39PWK will hurt the fuel mileage, but like stated above, it uses more fuel and air, which when adding more of both your adding HORSE POWER!

 

Like I said before, a bigger carb won't kill your gas mileage, but BIGGER JET"S and any other engine and exhaust mod's will. If anything, it will let it breathe easier.