Join Our Mailing List

Honda TRX 450R HP4 Valve Train Kit
Part Number: DR-108K

TRX 450R HP4 Kit with Porting and SERDI Cut
TRX 450R HP4 Kit
Titanium Valve KIt
Price: $1,050.00
Availability: CALL US!

Note: This is a specialty product and is not currently available for purchase online. Please call Duncan Racing International and a DRI staff member will assist you by collecting the required specifications and placing your order. Thank you.

Product Information:

With today's modern ATV 4-Stroke engines, making additional Horsepower is no easy task...This makes it critical that Engine Tuners have the Experience, Knowledge and Equipment to do the job properly.

Duncan Racing International's HP4 Valve Train Kit is designed to give you the utmost in performance and reliability by using the most advanced equipment and techniques in the industry. All porting work is performed by our master technician and valve seat cutting is done on our in-house SERDI valve grinding machine..

DRI HP4 PURCHASE OPTIONS (specify model year ’04-05 or ’06-‘16)

DR-108K $1195.00 DRI Valve Train HP4 Kit (04-09) Camshaft (see cam profile options below), HD Valve Springs w/Titanium Retainers, Shortened Valve Guides, Big Valve Kit (+1.0mm S/S Intake and Exhaust Valves) Porting Not Included
Kit must be installed by a trained professional

DR-108KP $1595.00 DRI Valve Train HP4 Kit (04-09) Camshaft (see cam profile options below), HD Valve Springs w/Titanium Retainers, Shortened Valve Guides, Big Valve Kit (+1.0mm S/S Intake and Exhaust Valves), Cylinder Head Porting , SERDI Valve Seat Machining and Professional Head Assembly w/Porting, SERDI Valve Seat Cut and Assembly*

*Customer must send in head for modification or purchase new head from DRI

DR-140K $1195.00 DRI Valve Train HP4 Kit w/O Porting/SERDI Cut (08-13)

DR-140KP $1595.00 DRI Valve Train Kit with Porting/SERDI Cut (08-13) *Uses internal compression

X11 Grind Camshaft
Motocross Cam (Midrange/Top End Cam, Lift: .430”/.385", Duration 266? °/282? °)

X22 Grind Camshaft
Baja/Cross Country Cam (Bottom/Midrange Cam, Lift: .412”/.350", Duration 260 °/268 °)

X33 Grind Camshaft
TT/Drag Race Cam (Maximum Top End Cam, Lift .435”/.385" Duration 276 °)

*DRI uses Billet Camshafts ONLY for the TRX 450R. No core required.
**To insure highest quality, all camshafts used by DRI are made in the USA.

*** '08 TRX450 electric start model uses different mechanism. Use part #140-grind #.
All grinds are available in #140 -X11,X22, X33

+1.0mm or +2.0mm Titanium Intake Valves add $200.00(pr) to kit price ($399.00 per pair if purchased separately)
+2.0mm Stainless Steel Intake and Exhaust Valves also available call for details

Big Bore Kits and alternate compression ratio pistons are also available to use in conjunction with the HP4 Kit. Check the Big Bore Kit and Piston sections on our site for more info.

In-House Cylinder Head Porting* (by Master Technician)
*Valve guides are removed during porting process to allow for greater port reconfiguration

Port Design Modifications Aided by In-House Flow Bench Testing and Computerized Port Mapping Software

Precision Valve Seat Machining and Reconfiguration*
*DRI uses in-house SERDI Valve Seat Cutting Machine used by F1, CART and NASCAR.

Big Valve Kits (Stainless Steel or Titanium)

Heavy Duty Valve Spring Kits*
*With Titanium Retainers, Mandatory with High Performance Valve Trains

AMPCO 45 Shortened Valve Guides

Camshafts of the Highest Quality Made in the USA

All Head Work Done In-House for Reasonable Turnaround Delivery Time.

Customers Can Send In Their Head for Modification or DRI Carries New OEM Heads.

HP4 Kits with porting offer gains up to 5 HP*.
*Results vary depending on camshaft profile and piston compression.

For maximum performance, it is highly recommended to use a Fat Boy 4 Complete Exhaust and Vortex Ignition with all HP4 Kits.

IMPORTANT NOTE When installing a high performance camshaft it is the responsibility of the engine assembler to check and confirm that the piston to valve clearance is adequate. Minimum clearance is .060" from valve to piston at peak lift. Tolerances can and will vary from engine to engine. There is no substitute for checking that these tolerances are correct. This is especially critical when mixing camshaft and pistons from different engine builders. One of the correct and easiest ways of checking this is by using the “claying the piston dome" method.
Call DRI or consult a professional technician

Related Item(s)
Code Name Price  
FB4-EH4560 Fat Boy 4 Complete Exhaust System '06-'16 TRX 450R $649.00
FB4-EH4500 Fat Boy 4 Complete Exhaust System '04-'05 TRX 450R $649.00
108-X11 Honda TRX 450R Camshafts $599.00
DR-1450 DR Chrome Front Bumper Honda TRX 450R $199.00
DR-16CG DR Chain Guard Honda TRX 450R ('06-'12) $29.95
DR-15CG DR Chain Guard Honda TRX 450R (2004-2005) $29.95
EK-145NT-47 Honda TRX 450R DRI National 470cc Kit $2,450.00
EK-145NT-515 Honda TRX 450R ('04-'05) DRI National 515cc Kit VARIES
EK-146NT-525 Honda TRX 450R ('06-'16) DRI National 500/510/525cc Kit $3,195.00
H224 Honda TRX 450 Billet Clutch Basket $259.95
K-FCR40-HT6 Keihin FCR Carburetor for '04-'16 Honda TRX 450R VARIES
PD-227 Pro Flow Air Cleaner Kit 04-05 Honda TRX 450R $139.95
PD-246 Pro Flow Air Cleaner Kit 2 '06-'16 Honda TRX 450R $149.95
QC-145N Honda TRX 450R Quick Change Clutch Cover $199.00
RD-LB215F Roll Design TRX 450R Lobo II Front Suspension Kit VARIES