the introduction of Bombardier’s DS650 and Yamaha’s
new Raptor 660R, Honda is going to need to step up and
release a big bore sport ATV. Today Hondas biggest sport
4-stroke is the TRX400EX, which is also
the most popular 4-stroke sport ATV available. The
combination of a good handling chassis and a reliable
4-stroke engine are the main reasons it has been such a
great seller for Honda. The owners of the 400ex’s
wanting more power are left with finding the extra
cc’s from big bore kits and other aftermarket power
accessories. Owning a 400ex myself, and doing a lot of
Dune playing I decided to check out what is available
for my 400ex. To start I contacted one of the best
engine builders in the 4-stroke field, Rick Ritter of
Ritter Cycle in St. Jacob IL. After speaking with Rick
on what options are available for the 400ex to gain more
power. He explained how to get more engine performance
from this model without reducing the reliability of the
engine. High performance usually refers to power output
of an engine, by using high quality replacement parts, durability
can also be associated with high
performance as well. To start with a 440 kit was chosen.
Rick receives the engine he starts spinning the wrenches
to take a look inside. He thoroughly inspects it,
including the transmission to see if any gears are worn
or for other parts worn to be replaced during the
assembly. With the motor now completely cleaned and
inspected, he begins the machine work.
installing a 440 kit the factory sleeve is removed and
the aluminum block is bored to accept the larger sleeve. After
the sleeve is installed it again goes to
the boring bar to be properly sized. He uses a Kwik-Way
boring bar, it is a quite accurate piece of equipment.
Doing this properly is a must!
While the cylinder boring is going on, he
also checks the crankshaft runout on the ends. If the
crank would need replacing now is the time to do it.
The Connecting rod is also checked.
After the cylinder boring is done and
the new sleeve installed he checks all
clearances to insure a proper fit of the new 89mm JE
piston that comes with the 440 kit. Next the cases are
reassembled , all bolts torqued to Honda factory specs .
The cylinder and piston are installed. The next step is
the Head / Valves / Cam /Rockers. Head porting DECREASES
how much power is needed to bring air into an engine.
When the engine can get air easier, it can send more
power to the tires. Good 4-stroke porting will not harm
reliability in the least.
step on the Head is to do a 3 angle valve job on the
freshly ported head. The most frequent and common
failures in a 400ex engine are the intake valves. He
replaces them with high quality Black Diamond valves.
The exhaust valves are also available, but many times the
exhaust are not in need of replacement. When Rick
replaces the factory cam with a more performance
orientated cam, he also recommends installing a set of
RcR Super Rockers. These hard welded and reground rockers
greatly increase the service life of the 440ex engine.
Rick always says "High performance, can also mean
With the cam in place using a special assembly lube the
engine can be completely assembled, timed and the
valves adjusted. The new 440cc engine can be expected to
run and perform at a much higher performance level than
a stock 400ex . Total gain in power is 50%over stock.
Rick Ritters price for this kind of job runs around
$1.300.00 which is a good deal considering the increase
in power, of course if you have other worn parts that's extra.
Some pricing is as follows:
Black Diamond intake valves...$64.00 per set
RcR Super Rockers......................$300.00
440cc kit including machine work.$400.00
RcR Head Porting and 3 Angle Valve job.$200.00
So to gain a 50% increase and not
loose any reliability the 440 kit makes for a smart
choice for the people who love their 400ex but want to
make sure those big bore newbies can’t leave you
sitting in their dust. It’s the kit of choice.
My next step is to test this 440ex against a stock 400ex
and a mild bore 415ex results to come soon, so
please stay tuned.
St. Jacob IL 62281