Custom Honda TRX680R

Big Bore Thumper ATV

Jul. 01, 2006 By Mike Lyon
 
Custom TRX680R Thumper!
    

      Jay VanValkenberg got sick of waiting for Honda to get off their duff and offer a big bore thumper ATV. Jay has been riding a big bore TRX250R for years. He bought it brand new back in 1989 and finally decided to switch over to a 4-stroke. Being a die-hard Honda fan he wanted a thumper that had plenty of torque and plush suspension. He decided a fully built TRX450R wouldn't satisfy him so he decided to build his own, fully custom TRX680R!

      Jay bought a XR650R motor from desert racer Mike Kay. The motor was built for a reliable desert racing motor by Rob Barnum of Barnumspro.com. It features a Carrilo rod mated to a custom 10.25:1 Wiseco piston (680cc) with Kibblewhite titanium valves and springs, a stage 2 HRC cam, hardened rocker arms, HRC HD cam chain, machine balanced crank, a 200 watt stator, and an all new clutch and rebuilt transmission. The motor came with a 36x42mm Edelbrock carb and a Big Gun exhaust. Jay bought an FMF exhaust, but ended up switching to the Big Gun for more power.

      Jay decided to have the frame built by Keith Marx of Motoquadchassiscomponents.com in Oregon. It?s a custom, one-off, chromoly frame, swingarm, a-arms, steering stem, and various other parts. Jay wanted the frame's geometry set-up similar to a TRX250R as well as being able to accept 250R parts. Keith went to work and came up with an amazing frame. It's a work of art! It features +2/+1 long travel a-arms and a 2" over '89 style no-link swingarm. For shocks he had TCS revalve an Elka shock to be used in the rear and had a custom set of TCS shocks built for the front. TCS claims 11" of travel in the front and 12" in the rear!

      For spindles and brakes Jay used some of his left over stock 250R parts and topped them off with HardKor front hubs and Braking rotors. In the rear Jay used his RPM axle, bearing carrier, and anti-fade axle nut which he had on his 250R. Jay topped the project off with an IMS 4 gallon tank, FuelATV.com front bumper and rear cooler rack, and a shiny, new set of red FullBore plastic!

 

 

      It took several months to complete, but once it was finished; and a few bugs were worked out; it turned out to be a monster of a machine! During a recent trip to the St Anthony sand dunes in Idaho, Jay got to dial this beast in and give it a good test run. He had to work out a few bugs with the major one being starting the XR motor. Due to the frame design, the OEM kick starter would not move downward far enough to allow the motor to start. The 1st few rides he had to be tow-started. Jay planned on adding an electric start kit from Baja Designs at some point, but ended up having it shipped to Idaho and installing it there. Once it was installed and set-up properly this electric start kit worked perfect.

     Riding this beast you soon realize it has tons of torque! You can lug it down to a near stall in 3rd gear, hit the throttle and it roars back to life. The long travel TCS suspension with a no-link rear suspension is ultra plush. The frame design allows this TRX680R to turn on a dime with zero bump steer. No steering stabilizer needed!

      Jay is very happy with his creation. It is set-up perfect for him, has plenty of power and couch-like suspension. It should turn out to be an ultra reliable dune machine which is exactly what Jay wanted when he started this project. Take note Honda, there is a market for a big-bore thumper!



 

   Engine:
Engine built by Barnumspro.com
680cc custom 10.25:1 Wiseco piston

HRC crank with Carillo rod , machine balanced

HRC stage 2 cam, HRC cam chain

Kibblewhite  Ti valves and springs with hardened rockers

Edelbrock 36x42mm Quicksilver pumper carb

Clutch: Stock XR650R

Exhaust: Big Gun modified for clearance

Machine balanced flywheel and counter balancer

Bajadesigns E-start kit

      Electronics:
XR?s only CDI
HRC coil
Spectrum 200W stator
Stock XR650R wiring harness
Trail tech regulator rectifier
Trail Tech MR-11 HID?s
FusionXtreme billet tail lights

Controls:
Bars: Flexx
Throttle: Moose thumb throttle
Clutch perch: Works Connection
Decomp lever: Works Connection
Brake lever: 250R custom trimmed.

 

 

 

Chassis:
Frame: Custom by Motoquad Chassis Components
A-arms:  custom +2+1 long travel by Motoquad
Swingarm: +2 '89 250R No link long travel by Motoquad

Steering stem: Custom by Motoquad

Front suspension: TCS 19." long travel triple rates 11? suspension travel

Rear Suspension Elka no link body, revalved and resprung by TCS 12" suspension travel

Spindles: Stock '89 250R
Front Hubs: Hardkor
Rear hubs: stock 250R
Brakes: Stock 250R (front and rear) with Braking rotors and pads
Rear axle, bearing carrier and anti-fade nut: RPM

Front bumper: FuelATV.com
Rear rack : Fuel ATV.com 

Powdercoating by BlakelyKustomKoatings.com

Plastic: Fullbore 250R

Fuel tank: IMS 4.0 gallon

Radiator: Afco Dual pass  250R racing radiator

Fuel cap: Project 321 billet/carbon fiber

Tires and Wheels : ITP Pro series Baja wheels Skat trak Hauler extreme 9 paddle rear with Sand Star front dual rib.

Misc.
Gearing: 14/39
Chain: DID Roadrace X-ring endless chain
Airbox: custom with 250R K&N filter

Nerfs : Blingstar Dana Creech style
Oil tank: Custom by Motoquad

Oil cooler: Earls 7 row Temp-A-Cure
Oil lines and fittings: XRP Braided stainless

Estimated weight: 375lbs

 

 


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