By: Dan Wade
LRD Performance Specialties in Gresham Oregon is well known
for their pro level engine building, and with that, their
dedication and focus is providing that same level to the
everyday rider. Arlan Lehman, LRD's head man, has the
philosophy of "We do not reserve quality and performance for
our pro riders. Each engine we build gets the best we have
because each customer is as important to us as our top riders
are. When I port your cylinder, I will put the same effort and
care into your engine, as the ones that has won LRD over 20
National championships." In todays economy, the almighty
dollar often wins out in favor of customer service and support,
and most importantly quality. LRD is a national level shop that
gives each customer personalized service and delivers high
While at DuneFest at Winchester Bay, Oregon, I had the
opportunity of a lifetime. I was able to get to test ride one
of the premier national level engine builder's personal quad.
Not everyone gets to make the claim to having ridden Arlan's own
ride. I met up with LRD's crew on a typically Oregon Coast
Saturday afternoon. I had anticipated this ride for some time.
Not only as mentioned about who's quad I was riding, but also
what it was. Arlan's bike is a full Lonestar and Custom Axis
chassis, but at its heart is what we were there for. The LRD
Pro-X 350cc Powervalve cylindered engine.
I had the opportunity to discuss the theory of the powervalve
with Arlan to great detail. The advantages the powervalve
provides are many. Arlan explains that "The main exhaust
port has a gate valve that lowers the effective roof of the
exhaust port at low rpm and raises it at high rpm." This
gate valve is controlled via exhaust pressure against a simple
diaphragm that over comes spring tension and will open the valve
as exhaust pressure increases, but allows the valve to quickly
come lower when the exhaust pressure lowers. The increase and
decrease of the exhaust pressure is tied directly to the RPM of
Arlan explains the theory of the exhaust port set-up "At
low rpm you need a low exhaust port roof (less duration). This
lengthens the amount of time the expanding gases from the
combustion process can push the piston down." Further
explaining the importance the exhaust port height at low RPM "The
slower moving piston also increases the opportunity for the
incoming fuel charge that is flowing out of the transfer ports,
to escape out the exhaust port, instead of staying in the
combustion chamber where it can be converted into heat energy.
By lowering the roof of the exhaust port at low rpm much more of
this fuel charge is captured in the combustion chamber which
increases low rpm power."
Arlan then explained how the exhaust port height affects
higher RPM power as well "At high rpm there is not as much
time for the fuel charge to be lost out the exhaust port. If
fact clearing the exhaust out of the cylinder becomes more of a
problem. The exhaust pressure must be out of the cylinder
before the transfer ports open, or the exhaust will blow down
into the transfer ports and at least interfering with filling
the combustion chamber." Continuing Arlan explains even
further "The exhaust port must evacuate the exhaust gases
efficiently or peak performance will seriously suffer. At high
rpm there is less time for this to happen. The higher exhaust
port increases the amount of time the exhaust can flow out of
the cylinder, and reduces the chances of the exhaust mixing with
the incoming fuel charge. The shorter distance that the
expanding gases from the combustion process push on the piston
is made up for by the occurrence of more combustion events."
How does all this tie into a powervalve engine? The
powervalve, as referenced to the above-explained importance of
exhaust port height, allows for variable exhaust port height to
match the RPM. Truly the best of both worlds, low port height
for low-end power, and a higher port height for road racer-like
top end power. When altering cylinder-porting arrangements, the
engine tuner is restricted to one port height for all RPM's.
That is why most engines are marketed under various packages
either Levels, Ultra-this, Spec such and such, Duner, MX. er,
etc, etc, etc. The powervalve engine via some simple changes
can allow for ONE engine to perform nearly all the above.
So how was the ride? I have had the opportunity over the
years to ride many different bikes by many, many different
engine builders. Each in their own right were unique. However,
the LRD 350 Powervalve, is at a level unto it's own. I swung a
leg over the quad, and kicked it. It was still warm, so no choke
was needed. One kick and it came to life. On a related side
note: Arlan understands how noise can adversely impact the ATV
sport, and in particular the sound restrictions that are in
place in the Oregon Dunes National Recreation Area.
The ODNRA sound restriction limits the sound levels to 93
decibels when tested. LRD has designed and implemented a new
silencing system that easily meets these requirements. Arlan had
the new quiet silencer installed on a chrome LRD 350D adjustable
I gave it a few moments to warm up and clicked it into gear.
I eased the clutch lever out and BAH, I killed it. What a spode.
I quickly recovered and started it again, this time getting used
to the feel of the clutch. No knock on Arlan's ride by any
means, I just wasn't used to where he had his clutch lever set
to engage, the engagement was super smooth with the RTC
easy-pull lever and the Hinson billet clutch basket.
I cruised off to a hummocky area to begin some of the various
type terrains I wished to throw at it. Again in my best spode
fashion, I about put it on the grab bar. This was at about 3500
RPM in 3rd gear & the engine has massive, amounts of low-end
power. That's the "hit" and that's it, at about off idle, the
power rolls on very strong, and that is the only real hard hit.
From there out the power is seamless, almost electric like. I
pointed the quad towards some small hills and purposely tried to
lug the engine and see how it would react. Stellar. The engine
would allow you to bog it, wick the throttle and it would pick
up power immediately.
I then headed to towards some tight trail like areas with
tall banks and some sharp corners to see how the power delivery
would be there. Again, stellar. The power delivery was smooth,
predictable, and consistent. I was able to really launch out of
a tight corner, with good control and speed. The engine made
itself very easy to ride. Where on other quads, I would have
been stirring the transmission, the LRD engine would allow me to
lug it in a gear, gain speed and RPM, but allow me to rev that
gear much further than I would have been able to on a standard
ported cylinder. I would compare this to being able to explode
out of a corner on a MX track, hold that gear down the straight
much longer, and harder, then enter another corner, and repeat.
The power delivery itself the whole time retained a near
electric like smoothness.
After giving it some trials in the tight stuff, I decided to
head out to more open country. Near the drag strip there are
some flats and some small roller hills. I was cruising in 4th
gear, almost clicked it down into 3rd to wick it and take off
across the flats, but decided again to lug it and see how it
responded. It shot off like a rocket. No need to downshift to
take off, the engine answered the input of more throttle and
took off. I clicked into 5th still holding wide open and
decided to see how well it revved out. There are many people
who have become of the notion that a larger bore engine does not
rev and does not rev out nearly as well as a 250cc engine will.
This engine even with 225 psi cranking pressure, revved up and
out very well. Back to the ride though, I held it in 5th gear
as long as I had room, I actually ran out of room before I felt
any drop in power indicating an over-rev, the LRD Hi-rev 250R
CDI ignition allowed the engine to rev to these high RPM's. I
was able to find a longer straight stretch and really gave it to
it hard. I ripped thru 4th and 5th, and clicked into 6th. The
engine pulled through each gear superbly and pulled all the way
to the top of 6th gear with 14/36 gears. The power and speed
Begrudgingly I had to return Arlan's bike to him, I went back
track-side and had to work to peel my fingers off the bars. I
was grinning ear to ear as I had very much enjoyed the ride and
was very pleased with the engine and it's characteristics.
In summary, I found that the LRD Performance Specialties
Pro-X 350cc Powervalve engine to be an excellent engine for any
terrain or abuse I could throw it's way.
It readily accepted being lugged and then repeatedly asked to
roost off like a rocket, as well as, accepted being spurred on
to near road racer RPM's and speeds down the flats. This engine
truly is a great all around engine that can and does make it
easy to ride with levels of performance most are not able to
achieve. The power delivery is consistent and predictable, as
mentioned the low-end power is stout, the mid range robust, and
the top end revealed itself to be equally impressive.
200 NE Victory Ave. #A
Gresham, OR 97030
Phone: (503) 661-6700
Fax: (503) 492-3747