2023 is the last year I will produce PORTED big bore kits with my own two hands.
I will continue to sell and market my custom pistons and gaskets and manufactured cylinders.
Starting January 1, 2023 you need to call or text for an appointment because I have limited space
in my workshop. No more sending engines without paperwork or a clear ability to pay for the work.
Text or call Eric Gorr for a time estimate and appointment (630) 825-5645

500 2-Strokes


All 2-stroke porting packages include complete porting, not the fake fluffy crap that most In and Out Porting and big time SoCal hop up shops offer. All of these porting packages include the following; disassembly and cleaning of all the top end components, complete porting and polishing, cylinder head machining, base machining, diamond honing, baking soda blasting, powervalve service or epoxy-filling, powervalve assembly and timing of applicable models.

 250-550cc BIG BIKES $225

Three powerband choices of more low to mid-range, more mid to top end or a smoother broader powerband, plus all of the services listed above.



In the glory years of the 500cc Grand Prixs in Europe throughout the mid-1980s and 90s, Eric’s CR500 tuned Hondas were the boss ride. Legends like Jorgen Nilsson and Leif Persson of Sweden, Rob Herring and Mark Eastwood of England, Jacky Vimond of France, and Peter Dirkx of Belgium owned the first turn at the GPs and turned the ultra-expensive HRC Factory bikes into insignificant bridesmaids. At the 1992 USGP at Glen Helen, Swedish champion Jorgen Nilsson holeshot the field in both motos.

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In modern days the Service Honda CR500AF’s have reveled in the praise of American dirt bike magazines for the last 12 years. Eric offers porting through Service Honda and in 2006 Dirt Rider magazine ran an Internet Bike Shootout and teamed with Service Honda. DR’s test riders demanded that a manual clutch be installed on the bike because the powerband was so smooth they thought the Rekluse auto clutch was slipping. The testers praised the porting and powerband with the smooth powerband with extra revs on top. You can choose the type of powerband and fuel type. Eric builds a lot of CR500s for mx, enduro, desert, hill-climb, dirt track, and ice-supermoto and oval racing.

The porting package on the CR500 includes cylinder porting, base machining, head work, manifold matching and polishing, epoxy porting, soda-blast cleaning, and diamond honing to the next oversize if needed for $200 Additional parts options include your choice of pistons from Wiseco Pro-Lite, Vertex cast&coated, Pro-X, and Wossner piston.

Yamaha Porting for Vintage YZ & IT465, 490, & WR500 $185

Starting with the first YZ250A in 1974, Eric tuned and raced YZ’s for years, In 1980 he teamed with Troy Bradshaw and hit the nationals. Troy pulled some awesome starts and great placings in the Trans-Am series and soon Team Keystone Yamaha’s suported Eric’s Flow-Ported YZ cylinders. In 1981 Keystone’s Jeff Hicks placed second to Danny “Magoo” Chandler in the Trans Am series. Magoo was also sponsored by Eric on a RM125 in the nationals that year. That series launched Jeff Hick’s career as a factory sponsored Team Yamaha rider and Magoo as one of the most fabled factory Honda riders of the 20th century.

In 1984 Troy Bradshaw made history at Loretta Lynn’s by winning the Open Class championship besting the factory sponsored riders from Yamaha and Kawasaki. The porting, cylinder head and carb tuning specs developed in that era can help your YZ run much better and be less sensitive to fuel quality and jetting.

Our comprehensive service package includes center-mandrel machining of all the gasket surfaces of the cylinder and head, complete porting and polishing of the exhaust port, epoxy-filling of casting flaws on applicable models, intake boost-ports bored and polished, head modifications, and diamond-honing.

Vintage Porting $185

Our vintage porting package is for bikes made before 1994 and covers all of the European Open class bikes like the Maico, Husky, SWM, KTM and Cagiva, We are very experienced with European bikes and we can still get oversized piston kits through Wossner of Germany.

Kawasaki KX500

Eric was the chief engine builder for TUF Racing in the heyday of AMA Open Class racing. By working with talented riders like Ron Lechien and Keith Bowen, Eric learned all the tricks to make the KX500s more reliable and ridable for a variety of applications like mx, off-road, desert, hill-climb, and ice racing. The complete porting package includes head mods and powervalve service for $225. The 525cc big bore kit with porting, replating, Wiseco Pro-Lite piston and gaskets is $660 and crankshaft stroking, rebuilding, and welding is $475 with a Hot Rod kit.

Head Mods and Button Decompressors

We offer head mods to lower the compression so big bikes run on pump gas and rev out better for only $35. We also offer more complex services like TIG welding and re-shaping and even button decompressor installation for air-cooled bikes for $85.

Bead-Blasting Bare Finish $35

We can bead-blast any stripped down engine parts to a bare finsih. We also offer custom powder coating services in factory colors.

Deluxe Cylinder Bore, Hone, and Chamfer (for iron-lined cylinders) $65

This service includes boring, honing, port chamfering and exhaust bridge relief, and cleaning. We stock Wiseco and Wossner forged pistons and Vertex cast piston kits for a 20% discount.