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Big Bore Stroker CR Mini
Big Bore Stroker KTM Mini
Big Bore Stroker KX Mini
Big Bore Stroker RM Mini
Big Bore Stroker YZ Mini
BB Stroker CR250 to 290
BB Stroker KX250 to 290
BB Stroker KTM250 to 290
BB Stroker RM250 to 290
BB Stroker YZ250 to 290
BB Stroker KTM300 to 340
BB Stroker KTM380 to 410
BB Stroker CR500 to 540
BB Stroker CR500 to 600
BB Stroker CR500 to 625
BB Stroker CR500 to 640
BB Stroker KX500 to 540
BBS Stroker KX500 to 600
BB Stroker KX500 to 625
BB Stroker KX500 to 640

Big Bore Stroker Build - CR640

Note:  A Liger Big Bore Cylinder is used for this Engine Build and because of the larger Bore size & larger Reed Block, the Intake track

is longer which sets the Carburetor back. Depending on your application, it may be neccessary for frame/shock alterations.

We can convert your stock Cylinder to a Big Bore 640cc, to avoid Carburetor clearance issues.

for stock big bore cylinder kit details & price, see the Big Bore Stroker CR625 page on the right side menu! (the only difference is bore size)



CR500 to 640cc

for year range 1987-01

Bore 98.0mm - Stroke 84.5mm

(637.4cc actual size)

 Nikasiled CP Industries Cylinder


(This kit is installed by us and not available as a parts kit.)


Because of the Custom machining and special processes that are needed to build your engine to these custom build specs, allow a minimum of 14 weeks for completion after we recieve your engine and payment.

(This engine build will easily add 25-30% more Power)

Your complete engine is required for this custom build, your Carburetor is not needed because one comes with this kit. Your CDI box & exhaust will only be needed if you would like us to run your engine, and you do not chose to purchase a pipe option.


Running a FMF or Pro-Circuit pipe with the longer stroke will give your engine more Top end Rev then the stock stroke, but may be held back from it's full potential because of its belly and stinger size. The TSR Pipe specs supplied with this kit is designed for the rpm range of this engine build. Your Keihin 41mm Pro-Series carburetor or your alternate choice will be set close, and should only require fine tunning for your altitude and/or riding conditions when you recieve it.


A replacement parts list comes with the engine for all custom parts used along with a spec sheet of your new bore and stroke, compression ratio,

Carburetor jetting, ect. The parts selected for this kit are available from any dealer that sells the product and are not modified after purchased, they are only custom parts to this application.


Your engine will get a complete rebuild along with all the machining work neccessary to build this 640cc engine. We will also machine & install a decompression valve for easy starting. The package price includes all parts listed below, labor and special machine work.



If you have any damaged transmission parts or any parts other then what is listed below, there will be an extra charge applied for the cost of the parts needed only, the labor for changing the parts is included in the package price.


Parts list:        (parts total this kit $3500.00)


  • CP Industries Liger Cylinder with Nikasil 98mm bore
  • 98mm forged piston kit 
  • CP Ind. head with replacable head dome
  • Larger reed block & custom intake manifold
  • Larger exhaust manifold & connector flange
  • Cylinder adaptor plate & top end gaskets
  • Decompression pop Valve
  • New connecting rod kit
  • Crankshaft main bearings
  • Transmission ball bearings
  • Water pump rebuild kit (shaft, bearings & seals)
  • Racing Clutch basket
  • Complete Performance 17 Plate Clutch kit
  • Complete engine seal kit
  • Complete bottom engine gasket kit
  • Keihin 41mm Pro-Series optional Carburetor
  • TSR Designed Custom Performance Pipe Blue Print to Build-it-yourself.

            Including cone layouts, instructions & weld-on Flange with O-rings


Labor and Custom work:     (labor total $1325.00)


  • Weld and machine crank wheels for new stroke
  • Rebuild & balance crankshaft with new connecting rod
  • Machine cases for stroker crank clearance
  • Machine cases for cylinder sleeve clearance
  • Machine cylinder for Decompression Valve
  • Stage I Porting, match & blend
  • Install new Racing basket on clutch gear
  • Clean engine and install new bearings and seals
  • Rebuild engine complete
  • Run engine on testing stand (optional)
  • Set up Jetting on 41mm Keihin Pro-Series or Lectron Carburetor


Inquire for your Custom Engine plus Options Order Form


RPM-CR640BBS8701   $4,695.00

(Regular package price $4,825.00)

Custom builds are available - Inquire with your request's

Return shipping charge is free if you live in the USA

International return shipping, flat rate $280.00


for placing an order or questions, contact  joep@rpmmfg.com  





We use CP Industries "Liger" Big Bore kits, for our CR600cc and larger Custom Engines

The performance information listed below came from our porting software, and using the port area & port timing along with a few other variables simulates what the HP at the crankshaft could be in a perfect world. The HP number listed below is not the actual HP of this kit, and in no way are we suggesting that it is. We are claiming a very conservative 25-30% power increase, and until a Dyno report is available, this is all we are claiming.






 Optional Carburetor Exchange

Lectron Tuned 44mm HV Racing Carburetor

(Regular Price $390.00) ---- Exchange Price $40.00

(exchange price is only available with cr625 or cr640 custom engine build)

Optional Billet Crankshaft exchange

"Limeted Quantity"

CR500 Billet Stroker Crankshafts

Inquire for availability


 CR500 Billet Balanced & Stroked Crank wheels

assembled with new Pro-X Rod & trued to Factory tolerances

Available Strokes: 81mm (+2), 83mm (+4), 84.5mm (+5.5)

Note: The 625 & 640cc kits use a 84.5mm stroke


Parts & Labor to Balance & Stroke your Crankshaft cost $655.00


CR500 Billet Balanced & Stroked Crankshaft assembly cost $749.00


CR500 Billet Stroker Crank exchange price $94.00

 (exchange price is only available with the purchase of 600/625 or 640 package)

Optional add-on's


RPM Designed "CR Liger" Removable Head stay mount with universal mounting locations

 for custom applications. Made from Billet 6061-T6 Aluminum with Viton O-ring sealing between

the mount and head, and (3) 75mm long head studs (replaces 3 standard length studs)


RPM-CR5LIG-HSMK    $159.00


This manifold fits the CP Industries CR Liger Cylinder's Reed Intake, It's designed to align the carburetor angle up to the stock air box. This manifold uses the 2 bolt type Mikuni rubber carburetor mounts with a 75mm bolt pattern.  Made from 6061 Aluminum, and comes with your carburetor mount choice, mounting hardware and gasket.


RPM-CR5LIG-IMAK    $219.00

(Specify what size Carburetor  manifold you need)

PVL Ignition with 17oz weight wheel $499.00

Powder Coating

Center Cases, Case Covers, Cylinder & Head $575.00

(price includes striping parts, mask & blast, mask & coat)

Custom hand built Pipe (with TSR software) $439.00

(Includes RPM Custom Silencer with 1.50 stinger mount)

FMF Pipe & factory 304 or shorty Silencer combo $329.00

Pro-circuit Pipe & Silencer combo $329.00

Replacement Big Bore Stroker Part's


98mm Wossner Piston kit # 8229D900-C  $219.00

98mm Wossner Ring set # RDC9800  $40.00

21mm Wrist Pin # S568  $18.50

21mm Wrist Pin Bearing # B1081  $18.95

* Liger Big Bore Gasket kit # CPI-LIGER-GAK  $56.80

Liger Big Bore Head O-ring kit # CPI-LIGER-ORK  $29.75

17 Plate Performance Clutch kit (89-01) # RPM-CR5CLU-17PL  $219.00

Pro-X Connecting Rod kit # 03.1406  $105.00

V-Force Replacement Reeds # 3P904A  $59.95

V-Force Reed Gasket # G3112  $4.95


* (Top end gasket kit contains a upper & lower cyl base & intake gasket)