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Roll your own Dual-Sport (part 2)
And now for the dirt!
Let's say you're 12 years old. You've got a well-used and well-worn-in dirt bike. Maybe
your dad, or your older brother teaches you how to ride and how to maintain your bike. You
learn to change the oil, adjust the chain, and make sure you've got the right pressure in
your tires. Every now and then, you ride the bike to the end of your driveway and back to
the garage. You stop, and look over your shoulder to the forbidden area, where you've been
warned that the police will take away your bike if they find it there: the street. Every
now and then, your little testing laps take you out onto that taboo zone... maybe you get
brave and ride to the end of the street and back, but you know you can never truly go
Part of this project of mine was to fulfill this boyhood desire of getting a dirt bike
onto the street. The previous section talks about how I did that... eventually, I did get
my plate. This section deals with the dark side... taking your homemade dual sport and
turning it into an off-road racing machine. This is truly the best of all worlds, and the
boy in me delights in ripping around the dirt and the road on my KLX331.
Figuring Out What's Needed
This winter was a very interesting winter. After doing the street mods to the KLX300
last summer, I took it out for the Vetra Dual Sport loop in Vermont. This 227-mile loop
consists of some awesome riding. It mixes relaxing rides on fire roads through the scenic
mountains of Vermont with some insanely hard uphill technical sections.
Imagine yourself riding up a waterpark's water slide tube filled with football sized
rocks, and you'll get the picture.
After the extensive highway riding on the KLX, and getting more familiar with the bike
during the off-road sections of the loop, I found that there were several things I needed
to do to take my experience to the next level. I already had a nice package that would get
me to the trail legally, but I now needed to maximize my ability to handle what the great
outdoors would throw my way.
The stock suspension worked fine on the hellish technical sections, but the bike didn't
have much top end for the highway, and the responsiveness of the motor wasn't all it could
be when I had to clear obstacles. Often, I would give it too much gas trying to deal with
the laggy responsiveness, only to rocket out of control when the revs finally came on in a
surge. The dual sport tires given me by my dealer also did not cut it. I had the original
rubber put back on (Dunlop K490/K695) but that's not quite street legal... so some work
had to be done there as well.
Banging away through the woods made my fingers nervous. The brush guards that came
stock on the KLX seemed fine for long grass, but not much more.
I needed more response, more power, more protection, and more traction.
The first area that I attacked was the responsiveness. Len Nelson's articles at
Motorcycle.com showed me the way to solve this (see the end of this article for
references). I immediately called up Larry Roeseller at Stroker Racing, and ordered the
pumper carb and head pipe what's known as the KLX Stage 1 upgrade.
Len noticed much more of
an increase in power than I did. This could be because I have a Canadian model, and he has
the US model, or it could be because I'm just a bigger guy. The Canadian KLX300 has 33hp
stock, compared to 27hp in the US, which is because of more restrictive emissions
equipment, I figure. The bike did have more pep though, and wheelies could be had simply
by pulling the throttle open in first gear, which is a big improvement over stock. The
cost associated with this upgrade was $340 for the carb, and $140 for the head pipe. The
stock head pipe was designed in 1837, or so it seems, and has a very tiny diameter. The
Stroker head pipe makes use of the full diameter of the exhaust port in the engine.
The stock carb is a Keihin 34mm CVK constant-velocity carb. In my opinion it is an
el-cheapo excuse which made its way into the KLX300 via the dual-sport KLX250 model in
Japan because Kawasaki had a bunch of them on contract already. It generates a
"smooth power response" which basically means, you open the throttle, and you
get power sometime in the future. I don't see how this is useful for anyone, let alone
dirt riders. The Mikuni 33mm pumper carb from Stroker has a machined velocity stack (I
don't know what that does for the carb, but it sounds good) courtesy of Stroker, and an
accelerator pump, like the YZ400F. You twist the throttle, and it squirts gas into the
cylinder, and your bike goes VROOM! That's the basic need there. The carb is 1mm smaller,
which aims at getting more grunt out of the free-revving Kawasaki motor. The carb upgrade
also comes with a Motion Pro throttle, which is much better to use than the stock bizzaro
Important note: installing the pumper carb is not a simple task. You are
required to have a grinding tool, and you must be prepared to take a couple of hours to
carefully grind some steel away from the head stay so that the carb will fit. The results
are worth it though! Be sure to grind enough material so that the carb does not bind, and
will be perfectly vertical. If the carb is not vertical, the floats won't operate
efficiently at high RPM, so you'll lose your top end power.
You also need to raise the gas tank by about a quarter to a half an inch. The more
room, the better, because the Mikuni carb is taller than the Keihin. You can raise the
tank by folding up a square of aluminum foil (make sure you compress it hard) over and
over again until it's a nice 2 inches wide by about 3 inches long and a half inch thick
brick. Place this on top of the rubber seat for the gas tank, towards the rear of the
bike, not the front. When the tank comes on, it will be a stretch to get the rubber clip
on to hold the tank down, but it does make it, and all of the screws should still line up
with the holes. If they don't, you might be too high, or you might want to try pushing the
tank forward a bit. I routed my throttle cable to the right of, and underneath the right
bar of the perimiter frame. It will be tight, but it should fit.
The next thing I wanted was some rip. Not just responsiveness off the throttle, but I
wanted some "Uh oh" feeling out of the bike when the throttle opened up. Again,
I dialed up Larry and he was more than happy to send me up a new cylinder and a Wiseco
piston, bringing up my displacement from 292cc to 331cc, about 14% higher. Installing it
was straightforward, and a more pleasant job than the carb which forced some grinding of
"unnecessary" frame parts which get in the way. Stroker also sells an exhaust
pipe, but after waiting a bit for it to be manufactured, I ended up going to an FMF
The MegaMax is a pretty cool pipe, as
there are three modes you can run it in: racing, spark arrested, and quiet spark arrested.
For my needs in building a racing dual sport bike, this is the perfect pipe. I can be
quiet in the city, and pop off the cap at the track.
With the bore kit, pipe, carb and header, I realized about an 8 hp increase, and a load
more torque on the bottom end, making the once-docile KLX300 a barn burner at 41hp.
I took off the silly Prince Charles-ears bush guards, and put on some Acerbis Rally
Pros. I'm not sure I would go with Acerbis again. They routinely deliver things which are
not properly sized for the application, and their tolerances are also pretty bad. You also
have to be prepared to fabricate some equipment whenever you're considering putting
Acerbis stuff on your bike. As is, the Rally Pro guards have performed fairly well, though
I've heard reports of them bending on hard hits. Next time, I'm going to use Enduro
I also put on some
Acerbis plastic frame guards, and they soon came off. Not because I took them off, but
before they had a chance to fully wear through and fall off that way, the zip ties that
come with the guards simply wore. The frame guards also wore away the paint on my frame
where they were attached, which is part of the problem they're supposed to prevent! Again,
Acerbis equipment just does not impress me. Larry at Stroker questioned my desire in
getting plastic frame guards, but I insisted, trying to save a couple bucks over aluminum.
I think the lesson is that when a guy who's won a bazillion off-road races makes a
suggestion, you should probably listen hard. Score one for Stroker, zero for me.
The stock DID rims don't get very high praise for
their ability to handle hits and not deform. I replaced mine with some Excels, though I
might also have done this for the trick look :-), well that was probably the only reason
though I'm trying to convince myself of the former. The supplier for the Excel Rims was MX
South, and Jeff gave me a good price.
The picture to the left shows a trick you can use to build a simple rim runout gauge.
Just clamp a simple tire pressure gauge to your forks so that the pressure meter rubs
against the outside part of the mounted rim. As you rotate the rim, the pressure meter
will be pushed back into the gauge by the high point of the rim. There will be a gap when
you reach the low point of the rim. You should be able to adjust the spokes until there is
no runout, in this manner. The picture isn't the clearest, as all I had was the polaroid
when I was doing the work.
Do not ride off-road
with Dual Sport tires. You're risking your life if you expect those tennis-shoe treads to
grip anything. After riding a while on my stock rubber, I put on a Pirelli MT-21 on the
rear. It definitely does not grip like the Dunlop K695, but it is a knobbie and is a world
better than the standard 70/30 dual sport tire. I competed in a Hare Scrambles on a pretty
tough enduro course on this tire. I wouldn't recommend doing that, of course, but unless
you're doing really heavy stuff, it's a decent tire. Dunlop makes a K695 model which is
DOT approved, and I'm going to try that next time. The image on the right shows the tread
patterns for the MT-21 series. Better than a tennis shoe, but it's not a racer.
I needed more top end speed for the highway sections between my trails. I went down to
a 48-tooth rear sprocket. It's a White Bros. "Titan Tough," which is a
repackaged Sprocket Specialists product, as far as I can tell. The bike makes loads and
loads of useable, grunty torque now, so I could afford a bit of a drop at the rear wheel
in exchange for dropping a few RPMs on the highway.
About the White Bros. "Titan Tough" sprocket: two things are for sure, it is
no titan, and it isn't tough. After one trip, I had bent two teeth slightly, doing nothing
unusual which would cause this, and after I derailed my chain in competition, I had broken
four teeth. Two in getting the chain off, and two getting it back on. The sprocket just
seems to be really soft. The teeth don't snap, but they can bend and fatigue, I gather, or
get cut, which weakens them before breaking. While this may have saved the chain, and let
me finish the race, I'm not sure that this sprocket would show any staying power in the
long run. I am switching to Renthal sprockets to see how they'll stand up. I'm not
discounting that I may have had a lemon sprocket, but I'm not going to take the chance
Speaking of the chain derailment, the KLX300 has
a very malleable tab to which the chain guide is bolted. A couple hard hits by rocks in
ruts can bend the chain guide, causing extra wear on the chain and sprocket. A very hard
hit, as happened to me, can bend the guide so much that it pushes the chain off the
sprocket, breaking teeth in the process, or snapping your chain. The solution to this is a
new chain guide from Stroker, which can be of two different models: a KX model which is
welded to your swingarm by the boys in the shop, or a trick billet aluminum part which is
far less bendy than the stock. I went the cheap route this time and got the billet part,
but if this happens to me again I'll send in my swingarm for the KX part.
The kids love it when you've got a lot o' stickers on the bike, and who am I to make
the kids sad? Really though, Stroker's service has been amazing, and the results are
equally great, so I'm happy to put their graphics on the bike. As well they threw in a
fender kit, and a shroud graphics kit for free when I did the cylinder upgrade, so on they
went. The changes are subtle, but very noticeable. The bike looks much more formidable
than with the stock graphics.
I smashed up my stock headlamp in a
crash... note, when it's cold out, the plastic likes to shatter! I replaced the stock
plate with a UFO model, which fit very well but was really for an XR400, and was white.
When I saw the Acerbis DHH headlight, I jumped at it! Of course, I was sorry when the damn
thing didn't fit right on anything with enduro equipment (like an odometer) or silly
unusual things like upside down forks. The look remains unusual though, and I keep the UFO
for racing, as it has my number on it. I try not to ride with the numerics on the street,
as that's just begging to be pulled over.
More Stuff To Do
The only thing I'd do to this bike now is to switch the springs, or change the
suspension outright. I'm too heavy for it stock (I'm too heavy for most bikes), so any
serious moto style stuff is going to give me fits. I don't really have the need for that,
as my riding seems to be more enduro style, so I'm going to hold off and make a decision
on this next summer.
(That's me with Ivo's girlfriend Nina, and a tricked out Geo Tracker that we
rented in Cancun. I'm not really 8 feet tall, Nina is very petite... Ivo took all of the
pictures on this page. His home page is here).
It took me a while to put this
whole project together. I started from scratch without having done any serious riding or
maintenance for about 15 years. By the time it was over, I had converted a dirt-only bike
for street use, and had torn apart the engine (to a small extent) and put it back
together, faster, and stronger than it ever was.
There were a lot of bumps and bruises along the way, and it certainly took a lot of
time and effort and heartache. Would I do it again? You bet! It was a hell of a lot of
fun, almost as much as riding the bike. I have a pretty unique machine now, one that rips
in the woods and can get me from point A to point B, wherever those points are.
These vendors supplied me with great support, and I advocate using them, and will
continue using them myself:
These equipment manufacturers made great products:
While I didn't deal with anyone at UFO, or the Excel people, or the Motion Pro people,
their products have been excellent.
The so-so stuff includes some of the Acerbis equipment, and the Pirelli MT-21 tires,
but only because I'm racing on those tires. They are an excellent choice for trail riding.
White Bros. also gets barely passing marks for shipping what's obviously a Sprocket
Specialists' product, and a weak one to boot.
The only major thumbs down in all of this is for Acerbis. Their equipment invariably
arrives and forces you to cut, bend, and splice, and/or completely fabricate parts in
order to use it. And, there's no guarantee if it will even fit your bike. They're also the
only vendor I called who would not ship anything to Canada. Come to think of it, their
website didn't even work properly.
Len Nelson's articles and email communication put me onto the trail towards modifying
my KLX, and without him, I wouldn't have been brave enough to do all of this work.
Everything that went on my bike, I did myself, and it's been a long while since I've had
the chance to do this kind of thing. Half of the fun in having a tricked-out bike is in
the building of it. Your own sweat and blood goes into the bike (literally, if you pinch
your thumb in the cylinder head :-), and that's what makes going out to the track and
roosting a much more fulfilling experience than it otherwise would be. You and your bike
blend together a bit, and your spirit and personality are forever embedded in that
wonderful and quirky collection of metal, rubber and plastic.
I'm happy I did this, and I look forward to when I can do it again, with a YZ400F. I
may have to wait until 2000 though!
You can read more about the KLX300 at the following articles:
Darcy Brockbank is a multi-semi-talented jack-of-all-trades. He spends his time
writing software, playing with photography, making noise on one of his guitars, and
(hopefully) riding his green street enduro. You can contact him at firstname.lastname@example.org or via the web at his home page.