|
| |
The Powroll
R&D CRF* project
150cc, water cooled, double overhead cam, four valve. Programmable digital
ignition, flat slide smoothbore pumper carb. Built in over the winter of
2000, the engine was a used as a proving ground for new development ideas.
*Hey, we thought of the CRF moniker before Honda released theirs! Powroll's CRF is a shortening of
the names of the two engines used, CR80 and
F from the CBRF3
which donated the head.
|
Big Guys on Little
Bikes?
For years, fathers have borrowed and subsequently thrashed junior’s
XR100. In some areas, the thrashing became so much fun that clubs and
events were founded which were devoted solely to racing four stroke minis.
This racing became popular with amateurs and pros alike. Businesses
started building parts for this new market. Stock chassis were weak and
broke under the stress. Chassis builders like BBR began to build high-tech
frames which were stronger, lighter and better handling than anything else
on the market.
Fortunately for this niche of racers, Powroll’s line of products has
always included go-fast goodies for the XR80
and XR100 (and now the
TTR 125, DRZ/KLX 125 and Honda's CRF150). Doubling the horsepower
on these little beasts was easy for us, we’ve been doing it for years.
Guy Cooper, Lance Smail, Rick Johnson, Jimmy Lewis, Steve Lamson, and
many others have enjoyed the additional fun provided by Powroll engines.
Although we build the fastest minis out there, minibike enthusiasts still
wanted more.
Many racers spent evenings in their garage concocting different setups,
but everyone had the same dream. What if someone made a water cooled
four-valve mini engine?
When the YZ 400F was released, the bar was raised for all four strokes.
Now everyone realized four strokes could be competitive (something Powroll
knew all along!).
|
Minibike racing became more popular, and
races like Langtown and the White Brothers Mini Nationals were getting
national coverage from the magazines and television. |
Lance Smail's 1999
Langtown Bike. Engine by Powroll, chassis by BBR |
A few years ago, Powroll and BBR teamed up to create the
dominant mini racers. In 2000, Powroll-engined BBR bikes won the Four
Stroke Mini World Championship (Rich Taylor) and garnered the top 3 places
at Langtown (Lance Smail, 1st; Timmy Wiegand, 2nd; Brad Hagseth 3rd).
|
In December, Powroll’s new R&D department began
talking about a completely new mini. One that was designed from the
ground up. A 2001 CR80 was purchased, and head parts from a Honda CBR
F3.
Head with
preliminary machine work completed |
Head with new
timing chain gallery cover installed
Completed head
with cover removed. Note external oil lines for lubrication of valve
train and underside of piston/rod
|
|
Although the design was easy to imagine, the actual
logistics of oil delivery to the head, cam drive and ignition mapping
were complex. Fortunately our R&D guru, Pete Fisher, had all the
answers! |
Crank after fine
balancing
|
|
Designing the cam
chain tensioning system |
Pipe fabrication
|
|
Initial fitting of
engine with chassis |
The chassis was ordered from BBR Motorsports, who were
also provided with a mock-up of the engine for the modifications
required. |
|
Started for the first time only days before it's
"debut" at the BBR 2001 Mini National, the sound is best described as
YZF-ish. Extremely fast-revving, with a sharp exhaust note similar to
a miniature Formula 1 engine. |
Research &
Development head guy Pete Fisher listens to the sweet sound of success
(yea, we know he doesn't look happy, but that IS his happy look)
|
|
|
 
DIRT BIKE MAGAZINE JUNE 2001
Quoted from the article shown
above...
AMA to allow 125cc Thumpers in the 80 class?
"Following the F.l.M.,
the American Motorcyclist Association is expected to lower four-stroke
displacement allowed in the 250cc class, from 550cc to 450cc for 2002. Also.
125cc four-strokes will be legal for the 80cc class. You can bet that Yamaha
is developing a YZ125F based on its current YZ80 and YZF technology. We
expect Yamaha to scrap the YZ426F in favor of a lighter, 450cc motor to meet
the new rules and go toe-to-toe with the Honda CRF45OR.
Powroll guru Pete Fisher
is developing a four-stroke minibike engine of his own, grafting a
CR8OR-Expert lower end to a four-valve street-bike engine. Fisher used a
water laser to cut one cylinder, head and cam from a four-cylinder 600 then
fashioned a cam-chain system and new liquid-cooling spigots to mate the
upper end to the lower. As for oil, Fisher is building a pump that works off
of the coolant impeller.
Brown Brothers Racing
already has a race-ready four-stroke mini, which is a hopped-up TTRI25
engine wedged into an aluminum-perimeter BBR frame with CR8OR Expert
suspension, hardware and plastic. Lance Smail won Langtown so handily that
Jimmy Lewis will be BBR/TTR-mounted this year. Currently a 150, the BBR bike
would have to be returned to stock displacement if the AMA goes with 125cc
as the limit. We’ve heard rumors of the limit being 150cc, but the AMA is
likely to go with the F.l.M. standard of 125cc four strokes at the fall
congress."
MINI
RACERS!
WANT THE NEW FOUR STROKE TECHNOLOGY
THAT THE 125 & 250 CLASSES NOW HAVE?
Contact the AMA - Tell them a 160cc four
stroke should be equal to an 80cc two stroke. 250cc four strokes
are allowed in the 125 class, and 450cc four strokes in the 250
class. A 125cc limit would NOT BE FAIR! |
|
Powroll CRF 150
Specifications |
|
ENGINE |
CHASSIS |
|
DISPLACEMENT
150cc
CRANK
Modified
CR80
CYLINDER
Fabricated
Powroll Billet
PISTON
Modified
Honda CBR F3
COMPRESSION
RATIO
Classified
HEAD
Highly
Modified CBR F3
PORTING
Heavily
Ported, Flow Bench Tested
CAMS
Highly
Modified CBR F3
OIL
DELIVERY SYSTEM
Oil
Pump built from highly
modified
Honda ATC pump.
External
braided steel lines.
IGNITION
Programmable
Vortex Ignition -
MT
Racing, Riverside CA
CARBURETION
33mm
Mikuni Flat Slide
with Accelerator Pump
AIRBOX
Modified
CR 80 with Titanium
air
inlet velocity stack
AIR
FILTER
Stock
CR 80
EXHAUST
Powroll
hand-fabricated thin wall
Stainless
with Titanium muffler |
FRAME
BBR
Big Wheel 80 Style, modified for sump clearance
SPROCKETS
Sprocket
Specialists, Oroville CA
CHAIN
DID
428 O-Ring
CLUTCH
Standard
CR 80 Clutch
OIL
Powroll
P40 Micron Moly
SUSPENSION
CR
80 Modified by BBR, Kent WA
FENDERS
Custom
Carbon Fiber,
Full
Bore Plastics, Portland OR
SEAT/PLASTIC
CR80/CR125
WHEELS/HUBS
CR
80/CR 80 Cermachromed
 |
|
 |
Project
bikes and engines are a great way to test new theories. They can also
be an excellent money pit with nothing to show for your investment!
Before beginning any conversion project, be sure you have the skills and
knowledge necessary (or know someone who does). Even seemingly basic
things like installing a four stroke engine in a two stroke chassis require
tons of skill and savvy. |
 |
