Another Jetting Thread (Jetting 406)

[kalebarellano]

Ok, I just rebuilt my 400ex, it is now a 406. I have a stock exhaust, I dont want to run a slip on cause alot of the ridding I do is not quite legal, and people dont really mind if I am not to loud. Anyway, what jetting would be good for these setups:

406
Stock Exhaust w/ drilled out the spark arrestor
K&N

Also what would be good for this setup:
406
Stock Exhaust w/ spark arrestor
K&N

Let me know know.

Thanks

[kalebarellano]

Oh, ya it is a 10:1 piston.

[Honda#4]

Try a 158 or a 160 main jet. needle in the 3rd slot from top and 3 turns out on the fuel screw.

[kalebarellano]

For which setup, are those jets for?

I have some jets laying around from my old xr400, so I am gonna see if I have what will work. Does the bore make it need bigger jets?

[fastyz85]

dude you got to get a full pipe. The stock exhaust is going to really hinder the power you could have plus it might even hurt your engine. I have a fmf slip-on now but will be upgrading to a curtis sparks x-6 shorty pretty soon.

[kalebarellano]

I actually have a t4 here, but it is just to loud. I do alot of riding from my house, and I just cant be that loud. I am thinking I will just cut out the spark arrestor, so it is just the end cap. I have my carb apart right now, cause my float was sticking and it was in-need of a cleaning.

I think this is the setup I will end up going with:
-406 10:1 compression
-Uni, Twin Air, or K&N
-Stock Exhaust (With Spark Arrestor Cut Out)

[Ruby Soho]

i run a 406 with stock exhaust too. except it has an endcap (dont think it changes it much but i heard it does something for it..)

why dont you get an exhaust and put a quite core in it?

[Honda#4]

Try a 155 or 158 main with the setup that you just gave last.

[kalebarellano]

Ok, I got the following a K&N and an outerware prefilter. I am going to cut the spark arrestor out of the stock endcap. I am also thinking about getting a rev box. Would the rev box change what jets I would need? Or could I go ahead and cut out the spark arrestor, install the K&N w/ outwares, and jet it. And then just add the rev box later?

Also is the 450 carb worth it? What kinds of gains would I experience with my setup?

Thanks

[dariusld]

The stock exhaust has to go no matter what. There are alot of threads on the stock exhaust and modifying it. No gains and a really horrable sound. But go ahead you will see for yourself. Modifing the endcap does nothing because the inside of the pipe is really small. Your not going to get as much gains from your other improvements if your just going to cork it up. I thinks it tough to get quiet horsepower. I know I sound like a jerk, but thats not what I'm trying to do. Sorry if thats how I came across.

[Quadtrax]

http://www.hmfengineering.com/index.php?cat=atv&prod=exhausts&series=Sport%20Series&searchby=pipe&make=HONDA&model=400EX

With a Quiet Core .... Under 96db.

[kalebarellano]

The endcap cut out thing really has no gains?

[dariusld]

Originally posted by kalebarellano
The endcap cut out thing really has no gains?

Here is a link from a really old thread. If you look inside the muffler, after you take the endcap off, there is a tiny hole your exhaust comes out, you have to modify that and that not easy. If you already know this ... sorry. I also have taken the endcap off. Hated it. I tried to modify the rest, but didn't have the right tools to drill a hole. Broke down and bought a new exhuast. Exhaust mod (http://home.earthlink.net/~gellett/exhaust/index.htm)