STAGE 2 TRAIL TRICKERY
Uncorking the stock 660 let it roar,
but Thumper wanted it to really rip
with more aggressive tires, and this
called for more power. The stock
100mm piston only has 9.2:1 compression, so there’s two areas right
there for even more bark and bite.
Wiseco’s 102mm piston has 11:1
compression and boosts displacement to 686cc, which is exactly what
the new Grizzly 700 displaces.
Russell the Ragin’ Cajun bored the
cylinder and installed the high-com-pression piston; Grizzly 700 owners
could go with this piston as well to
boost torque and performance.
Thumper Racing’s big-bore kit
includes piston, rings, pin, circlips,
gaskets and jetting for the BSR
42mm Mikuni carburetor. Russell
used the Dynojet kit’s richest main
and set the needle on the fourth clip.
This kit and boring the cylinder costs
$404 if you do work yourself.
Since the Grizzly now needs more
(93-octane) fuel, it wouldn’t make
sense to keep the exhaust corked, so
FMF provided a Powerline slip-on
muffler and spark arrester, which
retails for 329. This machine is rid-
den exclusively on private lands, so
the louder muffler isn’t an issue; own-
ers who ride on public land will want
an FMF Q exhaust, but we were
going big. Not only does the FMF
pipe let the big Griz breathe, it saves
four pounds over the stock exhaust.
Next, Thumper wanted better trail
traction, so the stock tires and
wheels gave way for AMS billet-alu-
minum wheels and GKT Wing
AT27x10-12 front and 12-12 rear
meats. TR also wanted more seat
traction, as the Stage 2 machine is
harder to keep between the legs, so a
Thumper gripper seat cover replaced
Sure enough, the Thumper Racing
686cc kit, FMF pipe and Wing 27-
inch tires really woke up the Grizzly
660. It’s more sure-footed in sand
Want to make your 2002-2007 Grizzly 660 into more of a trail terror or even a
mud monster? Thumper Racing and Wiseco can help turn the 660 into a Grizzly
700 with more compression.
Thumper bumped displacement to 686cc
with a 102mm piston, then ported the five-valve head and installed a hotter cam to create a Grizzly 700-beater that can pull whatever tire you want..
An FMF Powerline exhaust increases power
and flow for riding on private lands in Texas
and Louisiana, but those riding on public lands
will want a quieter Q muffler.
Thumper Racing has serviceable oil filters for
all popular ATVs for $69-139. Remove and
clean (from the inside out) with contact
cleaner, and it’s ready for some fresh oil to filter.
For trail use, the Stage 2 Grizzly 690 was fitted with
27-inch GKT Wing tires, which are more aggressive than the
stock rubber but still deliver a comfortable ride.