For 2-stroke Cylinders and 4-stroke Cylinder Heads

Porting is a metal machining operation designed to enhance the powerband characteristics of an engine, especially with aftermarket bolt-on accessories like exhaust and intake products, stroker crankshafts, big bore kits, and camshafts.

Forward Motion offers all-inclusive porting packages for all types of 2-stroke and 4-stroke engines used in dirt bikes, ATVs, snowmobiles, and shifter karts. Eric Gorr does all the porting himself and has worked with porting tools since the early 1970s and ported over 50,000 cylinders. More than all the other popular hop-up shops combined.

Eric is well trained in the use of the latest software programs that the factory teams use like the ones available from Professor Gordon Blair www.professorblairandassociates.com these programs are the standard in state-of-the-art design of championship winning motorcycle engines and recognized by the Society of Automotive Engines www.sae.org

Eric made his reputation on porting and does all the work his self, no illegal aliens, space aliens, or third world slave labor. It’s just middle-aged fart-knocker labor from one of the oldest and most experienced tuners in the world, whom still actually rides motocross, dirt track, trials, and supermoto.

Eric uses modern computer design software to do the number crunching needed to reconfigure cylinder ports to enhance the powerband to the way you want it to be. Eric is the only tuner in motorcycle racing with two US Patents, a published SAE technical paper, and six motorcycle books to his credit.

Cylinder porting can improve the reliability and ride-ability of your bike, and all the top end parts need to be modified as a set like in these package deals.

2-STROKE PORTING PACKAGES

All 2-stroke porting packages include complete porting, not the fake fluffy crap that most In and Out Porting or 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.

50cc AUTO BIKES $75
Cobra, KTM, Polini; cylinder porting with head mods to push the limit for advanced riders.

65-112cc MINIS $125
Your choice of porting for powerbands that work best for beginner and trail riders as well as national caliber experts in Supermini classes.

125-200cc BIG BIKES $150
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.

250-550cc BIG BIKES $200
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.

SCHOOLBOY/JUNIOR NATIONAL LEVEL MX 125 PORTING $125
This service includes cylinder porting and race-ready honing to a new OEM cylinder. You can supply your cylinder or we can sell you a brand new one for the price shown on the 144 page, or about $325
The porting powerband choices include stadium (low&mid hit) and outdoor (mid-top). Head mods and powervalve service extra. Quantity discounts for teams and clubs.

HONDA CR500s
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.

In modern days the Service Honda CR500AF’s have reveled in the praise of American dirt bike magazines for the last 10 years. In 2006 Dirt Rider magazine ran an Internet Bike Shootout and www dirtrider.net 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 change.

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. Additional parts options include Wiseco Pro-Lite piston kits $125, Cometic stainless steel gaskets $25, and top end bearings $15.

Recommended accessories? Boyesen RAD Valve, Kehin 39PWK, FMF Knarley, and a Service Honda ignition.

VINTAGE BIKES $125
Eric raced motocross since 4-strokes were popular the first time (1970) with his Ducati 250 Scrambler. Working as a mechanic and tuner since 1971, Eric has accumulated porting specs from all sorts of sources like factory racing directives, practical experience, and the use of modeling software. You might say he’s a bit of a vintage freak and sympathetic to vintage meisters like yourselves.

Eric is particularly skilled at Maicos and Yamahas, and works on all brands of Japanese and European motocross bikes. If you are a vintage freak and have historical specifications that you would like machined to a cylinder, Eric will cater to your needs. He has also ported cylinders to exact historical factory specifications from Harley Davidson Racing directives from Dick O’Brien to Team Green to Yamaha Wrench Report and even Swedish-language blue-prints from Husqvarna. If you have an antique cylinder with a cast-iron sleeve and you want to preserve the bore size, we can have the cylinder bore nickel-composite plated for an additional $225.

YAMAHA YZ465, 490, & WR500
Starting the first YZ250A in 1974, Eric tuned and raced YZs. 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 sported Eric’s Flow-Ported YZ cylinders. In 1981 Keystone’s Jeff Hicks placed second to Danny “Magoo” Chandler in the Trans Am series. That series launched Jeff Hick’s career as a factory sponsored Team Yamaha rider.

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 DGY-sponsored racer Troy, led a team of fellow champions that eventually included Doug Henry, Steve Lamson, Rusty Ott, and Jimmy Button. Eric worked as Troy and Rusty’s engine builder and mechanic at the Amateur Nationals for years.

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.

Services include 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, diamond-honing to next oversized Wiseco piston $185 Wiseco top end kit $150 extra

SHIFTER KARTS $125
What a sick twisted form of racing! G-Forces that will give you kidney failure and the ability to cut lap times faster than an Indy car! Eric offers a wide range of services ranging from cloning old cylinders to setting up specs for mx class and IC engines and even clay-oval outlaw racing. Eric specializes in CR125s and also handles all the IC engines like the Pavesi, TM, and CRC,

Eric performs cylinder porting and matching head mods, along with diamond honing of the bore for only $125.

CLONE PORTING $125
Racers are a superstitious bunch and if you have a cylinder that is trashed and you need a new one cloned to the old one for good luck sake, Eric can fulfill your wish. He’ll even engrave logos so close that you won’t be able to tell the difference from the original.

RELATED SERVICES

CYLINDER BASE and HEAD MACHINING $50
Cylinder head and cylinder bases can be turned and machined to produce a powerband that is better for beginners and trail-riders. The technical reasoning is that this modification serves to retard the port timing and increase the squish velocity produced in the cylinder head. If you just want more low end and don’t want to spend a fortune, this is the best mod that will give you the biggest bang for your buck!

CYLINDER HEAD MODS $30
This service includes all machining modifications per situation and application. Services include gasket surfacing, turning, clearance-machining for big bores and or strokers, flat-top piston conversions as well as hemi and conical dome shaping, lowering compression for low octane pump gas with ethanol, raising compression for high altitude, TIG-welding, o-ring groove cutting, plug-hole turning and threading.

POWERVALVE SERVICE $30
Powervalves are built into the cylinder around the exhaust port. They’re supposed to make the exhaust port bigger when you twist the throttle open. Powervalves are complicated mechanisms prone to failure. We offer a service to clean, inspect, and adjust the powervalves. This service comes standard with all porting and big bore packages.

CRANKCASE PORTING $30-$75
Crankcases can be improved with porting and a set of new ceramic bearings and Teflon seals. Crankcases can be ported for smooth transitions to the transfer ports, clearance mods for big bores and stroker cranks, re-surfacing or even welding or epoxy repairs. Send a set of bare cases or with your cylinder.

CYLINDER PLATING (aluminum cylinders) $225
Most modern dirt bikes use hard coatings applied directly to the aluminum cylinder bore. Nickel-composite plating is the hardest low friction coating available. We can plate a cylinder back to original size or to a big bore size for no extra charge. 1-Year warranty

CYLINDER PLATING (iron cylinders) $225
This service is especially for vintage cylinders with cast iron sleeved bores and CR500s. It is designed to preserve the bore at a particular size. Nickel-composite coating that is very hard and long wearing and comes with a 1-year warranty.

BORING and HONING for iron-lined cylinders $50
This service includes cleaning, boring, diamond-honing, port chamfering, exhaust bridge relieving and polishing. We offer Wiseco, Pro-X, JE, Athena, Magnum, and Vertex piston kits as well as generic gaskets and bearings.

4-STROKE CYLINDER HEAD PORTING PACKAGES

Eric bought his first Superflow flow-bench in 1978 and tested with it for three solid years while working at a Chicago area motorcycle speed shop that specialized in roadracing and drag racing. He was the first engine builder to adapt a flow-bench for use with a 2-stroke cylinder. Because of the high cost of individual flow-testing, Eric’s headwork is flow designed. In other words the flow-testing is performed to one head and a mold is made of the perfected port. 4-Stroke porting is all about matching the ports to the valve seat and having the correct angles and widths of seat angles. Eric has tons of data on ports, cams, valves sizes, cylinder sizes and how they work to produce a certain powerband.

Eric’s 4-stroke porting is mainly sold with a valve job and assembly with valve shimming, but he also offers porting for new bare heads.

PITBIKE PORTING $75
This package is for the typical 2-valve hemi clone of a Z50. Includes disassembling, cleaning, inspection and measurement of components, porting, single and valve seating, matching the ports to optional aftermarket accessories (high flow manifolds and exhausts) valve cleaning or replacement, lapping, baking soda blast cleaning, gasket surfacing, and assembly.

NEW HEAD PORTING $125
This service is competitively priced and strictly for new bare heads. We can supply you with new OEM heads for leading mail-order prices. In fact we’ll beat they’re online price by $1 (Service Honda, World of Powersports, Motorsports Outlet).This porting package includes complete porting but no valve job (not necessary). The intake is matched and roughed and the exhaust is polished and the gasket surface lapped to a finer finish.

PORTING WITH VALVE JOB $300
This service is for 4 & 5 valve heads with decent seats and guides. It includes disassembly, cleaning, inspection and measurement of all top end components, complete porting and surface texturing (rougher intake and smoother exhaust) Serdi multi-angle valve job, cam bearing honing (RMZ,KXF,YZF) baking soda blasting, cleaning, guide replacement if needed, gasket surface lapping, valve-train assembly with new seals, and adjustment.

VALVE SEAT REPLACEMENT WITH PORTING $500
This is the same service as above except we include seat replacement with CV4 copper-beryllium valve seats, especially for CV4 titanium valves. The seats are included but the valves are extra and priced per application.

RELATED SERVICES

CYLINDER BASE and HEAD SURFACE MACHINING $25
When 4-stroke engines are over-heated or run out of coolant the heads and cylinders warp and cause chronic leakage problems. We can fix that by using a surface grinder on the head or turning the cylinder on a lathe using a precision-ground expanding mandrel. Sometimes it is beneficial to reduce the clearance between the piston and head with cylinder base machining. This is done on an application basis and especially available to tuners who take precise measurements.

CYLINDER PLATING $225
Nickel-composite plating is used on all modern racing motorcycle and racecars since 1980. Eric used his experience working for a leading F-1 vendor in Europe to integrate Formula 1 technology into every part of the plating process from torque plates and fixtures to platinized-titanium anodes and pre-honing to produce a grain structure. The honing is performed on a Sunnen CNC machine using 12-point diamond mandrels custom-made in Germany. This process insures that the honing is perfectly round. The price of $225 includes free over-sizing to big bores and a 1-year warranty for the plating.

BORING and HONING (for iron-lined cylinders) $50
If your engine has a steel sleeve, is an XR, or a pitbike, we can bore and hone the cylinder to a Wiseco big bore piston or one that you supply.

Telephone Orders Call 1-630-825-5645
Email: ericgorr@hotmail.com