My wife and I put our new Raptors through their paces this weekend (we have sore butts to prove
it!) and we had a lot of fun. We still have one concern that I've voiced here before, but we still
don't know how to solve it.

We can't get any low end torque. Tons of mid-range to high-end, just no low end grunt.

After we got home, I tore into the entire intake, and stock, these units are really constricted. So
opening them up so they can breath looked straight forward enough, but the stock exhaust didn't
have many options. The only baffel(s) also contained the spark arrestor. There were some fins on
the rear of the baffle that look like they could be removed, and one could probably drill a few holes
here and there, but basically it looks like Yamaha didn't plan for folks to modify the stock exhaust much.

Since we are looking for low end, it seems like a slip on silencer would be better than a full custom
exhaust as most of the dyno's show these systems increase top end, while sacrificing low end. The
Raptor head pipe design looks pretty sound up through the mid-range.

After burning the midnight oil on Google, it looks like White Brothers and Yoshimura are good choices.
With K & N air box mods and re-jetting, do you all think that we are on the right path? We want the
widest torque curve possible that comes on as early as we can get it (hopefully below 4,000 RPM).

 

I ran an open airbox, 48/50 jetting at sealevel using Dynojet jets and needles, and GYTR carbon fiber tip. It had plenty of low end torque. Another simple change is to modify your gearing. I ran 12/42 sprockets.

/Jon

 

I agree, change to 12 tooth counter sprockets. A lot of people pull the baffle out of the stock exhaust until they switch to an aftermarket one.

 

Jon, in going from the stock 3.08 final ratio to a 3.50 (your 12/42 setup) did you notice that you
got a lot more front end snap? I ask because we went through one really steep and rocky technical
section that required a lot of throttle control along with some careful clutching as well. In this section,
our Raptors were pretty jumpy and hard to keep down. We got through, but both clutches were hot.

 

i run a full HMF with airbox mod and it has TON OF LOW END . i also run a 12 tooth front sprocket . this week i switch to a 12/42 sprocket ... MAN best thing i ever did!!!!! . i just went on a poker run of 36 miles of the tightest woods u have seen ... the gearing worked perfect i could lug second gear almost any where which stopped the frontend jumping like you said.. ..... i recomend this mod

 

rupezx,

Since the 12/42 mod requires changing both sprokets, did you have to lengthen your chain or
did you get enough range from the adjusters on the swing arm? This sounds like a great mod
for technical trails while I decide on the intake/exhaust mods. So far I'm leaning towards a
K & N filter w/mount and a White Brothers E-Series slip on silencer. This should help the lower
and mid-range while leaving the top-end pretty much alone.

 

bopeep , i still have my stock chain on it , but i also have about a year on the chain. i had more then enough adjustment for the sprockets. the only close part waz the skid plate ,but it fit to without spaceing it down

 

rupezx,

So, you read my mind. Last night I sat out in the garage and tried to understand all the
issues with this upgrade. This is what I came up with:

1. Having enough play in the chain adjusters on the swing arm to use the stock chain. BTW,
the notches on my adjusters are not even on either Raptor. I'm wondering if they square up the
backend with something else in Japan other that these as a guide.

2. After removing the chain, it looks like the rear sproket can be removed by simply removing
the left, rear tire and slipping the sproket over the wheel mount. It doesn't look like the axle
needs to be removed.

3. The stock swing arm guard literally touches both the sproket and the rear brake disk. It looks
like this will need to be shimed with some field washers, etc.

Anyway, I look forward to starting work on this upgrade as we sure are putting a lot of stress on
our clutches having to ride them as hard as we are over the nasty stuff.

 

Congrats on the Raptors...If I may put my 2 cents worth in I would say these were all good ideas...I had the same problem so I went to a 12/40 setup because I didn't want to sacrifice to much top end.When I bumped my front sprocket down one tooth I noticed about a 10% decrease in top end (I can only top out at about 73m.p.h. now according to my g.p.s.) but I also noticed a 10% increase in bottom end...then I put on the White Bros.R-4 exhaust, Pro design foam filter and bumped my jets up to a 150/155.Boy did that thing wake up. We don't have alot of Pinetrees here in the desert giving us plenty of oppertunity to open 'em up on the straightaways so speed was still somewhat of an importance in my decision... I would love to try the 12/42 combo some day though. Good luck.[img]i/expressions/face-icon-small-smile.gif[/img]

 

We are pretty much solid desert here as well in SW Idaho, just a lot more rocky stuff based
on magma (old lava). The Snake River Plain and surrounding mountains are fun to ride in,
but your equipment sure takes a toll! Of the lower 48 states, Idaho has more public lands
than anywhere else (other than Alaska) so we have literally hundreds of miles of continuous
trails.

Since we are too old to be real top-end freaks, (can you ever be too old!), moving 10-20% of
the torque curve is fine with us. 60Mph is plenty fast for me!