A TWO-STROKE MASTERPIECE
Duncan Racing builds an awesome Banshee
By the staff of Dirt Wheels
Photos by Pat Carrigan (Yeah, my photos are dark and out of focus, but Pat can fix them.)
A TWO-STROKE MASTERPIECE
The iconic Yamaha Banshee has found a place in the hearts of thousands with its two-stroke, twin-cylinder, fire-breathing engine. They scream and sing over dunes, rip through the desert, and are even seen looping around racetracks and negotiating tight trails.
After an amazingly long run, Yamaha eventually ceased production of the Banshee in 2006 for the U.S. market. That means there are a good number of YFZ350s on the used market. Duncan Racing (DR) offers some of the best upgrades for the two-smoker and has helped put them on podiums throughout multiple countries, which includes Baja 1000 victories. Recently, DR was tasked with turning this Yamaha from old to gold with some of the best components in the industry.
A TWO-STROKE MASTERPIECE
IT BEGINS
Building a project ATV this labor-intensive is not a task for the feeble. It takes time, dedication, and research. Or, you can trust Loren and Lenny Duncan and their many years of experience to put together a piece of art that shreds! They started by disassembling the machine down to the frame for a gusset kit and fresh powder coat.
Moving on to making the Banshee a roller again, DR began installing the suspension. On the front end, Roll Design’s LOBO II Desert kit found a home. The kit includes Roll’s gullwing A-arm set, tie-rods, Stage 5 Elka long-travel shocks, and Crown steel-braided brake lines and line clamps. Attached to the ball joints on the arms are Yamaha YFZ450R spindles and hubs. Doug Roll designed the kit specifically to work with the YFZ450R parts to improve the steering.
A TWO-STROKE MASTERPIECE
A Roll Design anti-vibe steering stem and handlebar clamp assembly were mounted up next. Attached to the stem is a GPR steering stabilizer. It makes a major difference in handling and steering. The owner of the Banshee requested a Fasst Company Flexx handlebar be installed to aid the suspension kit in making the Banshee’s front end as plush, controllable, and as comfortable as possible. Moving backward, a set of Roll Design footpegs was installed with Duncan’s custom heel guards.
The rear of the Yamaha was next. A Roll swingarm was installed, along with an Elka linkage and a Stage 5 long-travel shock. The Elka shock has two compression adjustments, rebound, spring preload, and a dual-rate spring setup. The fronts are similar. Next, an RPM Dominator II wide axle was run through the carrier and tightened down.
Eventually, both Sunstar sprockets were mounted up with an RK Excel chain, and Galfer brake rotors were installed as well. Duncan picked up Yamaha YFZ450R front and rear brake calipers and custom-made the rear mounting bracket to be able to install all three brakes on the 350. DWT front and rear Beadlock wheels were wrapped with STI Tech 4 tires and then mounted to the quad to make it a roller.
A TWO-STROKE MASTERPIECE
TOO MUCH TWO-STROKE
Before the engine found its home back in the frame, Loren Duncan placed it on his bench and cracked it open for a full rebuild. Every single OEM part gets cleaned, inspected, and replaced if needed with their rebuild service. However, the owner of the Yamaha craved more power but demanded that the engine remain reliable, so a Duncan Racing/Paul Turner Racing National midrange kit was installed.
The kit has PTR midrange pipes, DR Fat Boy silencers, porting, a PTR Powerhead, Pyramid reed valves, MasterFlow intake manifold, DR pre-jetted Keihin 34mm PJ carburetors, a jet kit, a K&N air filter setup with outerwear, spark plugs, and technical instructions. Duncan Racing offers their tech support with the kit. That was just the start!
DR continued with their flywheel mod, Super Flow carb mods, a shift star mod, their water pump drain cover and pump cover, an adjustable stator plate, as well as their billet stator cover. The engine gained a DR quick-change clutch cover mod and a billet gear shift lever. The clutch components consist of Hinson Racing’s billet clutch basket with the cushion kit, but the clutch plates are Duncan Racing’s C33 kit.
The highly modified Banshee engine found its way back in the frame before the exhaust pipes could be installed. The Paul Turner pipes were triple-chromed before installation, with DR’s custom pipe clamps included. Instead of utilizing the old stock radiator, Lenny mounted a CBR Performance radiator in the frame.
A TWO-STROKE MASTERPIECE
BUTTON IT UP
Once the engine was installed and the chassis was a roller, the rest of the components could be included in the build. Lenny took a 1/2-inch-thick poly skid plate from Campbell Racing Fabrication and modified it to fit perfectly under the Banshee. Moving on up, the air intake was installed with Pro Design’s Pro Flow air-cleaner flange. Once the IMS fuel tank and the Banshee plastics were mounted to the frame, the recovered seat with a Pro Top cover was clipped back onto the 350.
Before some of that occurred, a set of Baja Designs Squadron Pro LED pods replaced the stock headlights. Duncan Racing didn’t like the fact that the lights would dim and brighten with rpm changes, so they visited Ricky Stator for a high-output stator, a voltage regulator, a battery-dimmer assist to keep the lights bright, and a switch to control them.
TESTING TIME
Combining some of the best parts in the industry onto one machine always makes us smile ear to ear. Upon sitting on the pristine build, we were mentally taken back to screaming up sand dunes and blasting berms on the two-stroke monster years ago. The performance of this Duncan Banshee is beyond almost any you could ever pilot, though. That was made apparent the instant we rolled on the throttle.
The engine fired up extremely easily with one kick. The “Shee” takes off smoothly and is very controllable if you are easy on the throttle. Once you start raising the rpm and pushing the plush Roll/Elka suspension setup, a blip of the throttle into the powerband will break the tires loose in an instant and send the whole quad sideways.
We tested the DR Banshee on a dry, desert-style motocross track, and we knew that if the STI tires could gain the proper traction, the Yamaha’s front wheels would rarely touch the ground.
The suspension was smooth and impressive. The chop was easily soaked up, and blasting over whoops was made easy compared to most any Banshee you could pilot. The rear shock was a little soft, but quick tuning fixed that issue. Doug Roll’s design of the Lobo II Desert suspension kit with the Yamaha YFZ450R spindles improved the handling and cornering characteristics of the 350.
The quad was flickable and controllable. As always, the Fasst Co. Flexx bar was the cherry on top to cut down on vibration and rough hits through the front end. We would have loved to take this build to some big sand dunes with paddle tires mounted up.
A TWO-STROKE MASTERPIECE
FINAL THOUGHTS
It was an epic experience for our staff to have some seat time on Duncan Racing’s latest two-stroke build. Their Banshee could have found a home in a museum, but it was meant to be ridden. Its owner couldn’t be happier to receive such an incredible build from these Banshee experts. We can still hear the sound of the throttle snapping open and the pipes singing two-stroke notes of pure happiness. Once again, great job on the epic build, Duncan Racing!
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A TWO-STROKE MASTERPIECE
PARTS & CONTACTS
BAJA DESIGNS: (800) 422-5292, www.bajadesigns.com
Squadron Pro LED pods $430
CAMPBELL RACING FABRICATION: (435) 632-4902, www.campbellracingfabrication.com
1/2-inch Skid plate/modified by DR $150
CBR PERFORMANCE: (951) 245-2900, www.cbr-performance.com
Radiator $399
DOUGLAS WHEEL & TIRE: (800) 722-3746, www.dwtracing.com
Front and rear Beadlock wheelset $749
DUNCAN RACING: (619) 258-6309, www.duncanracing.com
Engine rebuild $695 + parts
DR/PTR National midrange engine kit $2395
Pipe chrome/triple chromed $195
Pipe clamps $69
Flywheel mod $95
Super Flow carb mods $60 each
Shift star mod $50
C33 DR clutch kit $199.95
Water pump drain cover $39.95
Water pump cover $99.95
Adjustable stator plate $99.95
Billet stator cover $350
Quick-change clutch cover mod $250
Billet shifter $89.95
Block-off plates $14.95
Frame gusseting/sandblast and powder coat $799
Chrome front bumper $199
Crown series steel-braided brake line: rear $39.95
Custom Chromoly heel guards $399
Graphics kit $149
ELKA SUSPENSION: (800) 557-0552, www.us.elkasuspension.com
Stage 5 front shocks: Included in RD kit Stage 5 rear shock $1,295
Linkage $495
FASST CO.: (877) 306-1801, www.fasstco.com
Flexx handlebar $359.99
Bar pad cover $10
GALFER USA: (805) 988-2900, www.galferusa.com
Rotors $119.95 each
GPR STABILIZER: (619) 661-0101, www.gprstabilizer.com
V1 ATV damper kit $549
HINSON RACING: (909) 946-2942, www.hinsonracing.com
Billet clutch basket w/ cushion kit $250
MAXIMA RACING OILS: (800) 345-8761, www.maximausa.com
PRO DESIGN: (714) 534-0620, www.prodesignracing.com
Billet water pump shaft $79.95
Pro Flow air cleaner flange $69
RICKY STATOR: (760) 787-0094, www.rickystator.com
Hi-output stator $229
Voltage regulator $24.95
Battery-dimmer assist $69.95
Switch $69.95
RK EXCEL: (760) 732-3161, www.rkexcelamerica.com
O-ring chain $85
ROLL DESIGN: (760) 731-5920, www.rolldesign.com
Lobo II Desert front suspension kit $3495
Anti-vibe steering stem $399
Anti-vibe handlebar clamp $99.95
Footpegs $239
RPM: (928) 771-9363, www.team-rpm.com
Dominator II axle $389.99
STI TIRE & WHEEL: www.stipowersports.com
Front 21×7-10 Tech 4 tire $65.99 each
Rear 20×11-9 Tech 4 tire $85.99 each
SUNSTAR: (937) 704-1462, www.sunstar-braking.com
Powerdrive countershaft sprocket 15T $26.95
Rear steel sprocket – 38T $45
WORKS CONNECTION: (530) 642-9488, www.worksconnection.com
Clutch perch assembly $149.95
YAMAHA
Spindles $389 pair
Front hubs $399 pair
Front and rear brake calipers $875
ZIP: www.zipracing.biz
Pro Top seat cover $199
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