Superminis &125 Big Bore Porting Start @ $375

Eric Gorr of Forward Motion is the Supermini and 144 Big Bore expert with 31 years experience, the most complete line of model coverage, the best prices, and the most comprehensive technical support. Call Eric for a consultation on building a big bore 2-stroke at 1-630-825-5645.

AMA and F.I.M. Rules for Big Bore 125s

People call all the time asking about the new rule changes here and in Europe. The AMA governs motorcycle racing in the USA and the F.I.M. covers Europe. In 2005 the AMA raised the displacement limit of 125s 20cc in order to better compete with the 250Fs. Our kits are legal for 125 Modified classes but not Schoolboy (12-15yr) or stock classes. The kits are also legal in racing classes where 125s race against 200s, as in dirt track, enduro, ice racing, and hill-climb. In America at the 2007 rules meeting, the AMA Congressmen tried to make 250Fs compete in the 250 class and bring back the old open class for the 450 4-strokes, but the AMA forestalled their request for a rule change until the next meeting in October 2007. The reason cited was that the motorcycle manufacturers and dealers had already negotiated orders for 2007 motorcycles.

The AMA turned down a request from manufacturers to allow production 144cc bikes to race in America, but that rule is up on the table for this year’s rules meeting.

For 2007 in Europe, our kits are legal to race in MX2, the world championship class. Next year there could be sweeping changes in national federations. The country of Belgium is the first to allow 144s to compete against 250Fs in professional and amateur championship competition. Look for France, Netherlands, Italy, and Germany to follow in 2008. The future for 125s looks brighter. In 2008 there will be 3 European manufacturers offering 144s, KTM, TM, and Husqvarna.

For 2008 the AMA Boosted the Maximum Limit to 112cc for Supers & 153 for 125s BIG BORE LONG ROD STROKER KITS are legal for AMA Amateur racing starting in February of 2008

COMPLETE KITS - WHATS INCLUDED

Our kits include everything you need including the piston kit, alignment pins, top end gaskets and bearing. Our big bore service includes boring, porting, cylinder head mods, Nickel-Composite plating, powervalve and crankcase mods plus re-assembly on applicable models. Also we take the time to re-machine any damaged gasket surfaces, Tig-weld casting or inherent design flaws, and inspect and polish the powervalves all as part of the basic big bore package price. If any of the powervalve parts need replacement, we’ll source them for competitive mail-order prices.

SUPERMINI MODEL CHART $375-450

Honda CR80/85 1986-2007 $375
Kawasaki KX80/85 1991-2007 $375
Suzuki RM85 2002-2007 $450
Yamaha YZ80/85 1993-2007 $450

BIG BORE MODEL CHART $450-495

Honda
CR125 1989-1999 134, 139, 144cc $450
CR125 2000-2004 134 & 139cc $450
CR125 2005-07 134, 139, & 144cc $475
Kawasaki
KX125 1994-2007 134 & 144cc $475
Suzuki
RM125 1990-2007 134 & 144cc $495
Yamaha
YZ125 1994-2007 134, 139 $475, & 144cc $495
GasGas 125 MX,XC 2004-2007 134, 139, & 144cc $495
Husqvarna
CR/WR125 2000-2007 134, & 144cc $450
TM125 2001-07 144cc $450

How to Choose the Best Powerband For Your Riding Needs

Porting is included with every big bore kit and powervalve and head modifications must be performed for piston clearance. We offer two basic options; more low to mid and more mid to top end. Big bores make more low-end power just because of displacement. Choosing more mid to top end gives a wider powerband overall. The more low-end option works great for heavier riders, off-road, stadium mx, and it’s the #1 choice of female riders because it gives a 125 a similar powerband to a 4-stroke. The best part is we offer free updates to the porting for two years and we’ll inspect and diamond hone the cylinder too.

Production dirt bikes are designed to burn race gas with octane of at least 98MON. We offer you the choice of race gas or pump gas, however in choosing pump gas we lower the compression ratio below stock and you will sacrifice a bit of potential but overall it’s still better than a stock sized engine. For riders who live and ride in the mountains at high altitude, we offer a special head modification to compensate for the lower air density. The Service Order Form has boxes to check for all of these options and you need to print that form from your web browser and send it along with your top end or engine parts.

What Size 125?

In the application chart above you’ll notice that there are as many as three displacement options; 134, 139, and 144cc. The displacement options are based on two factors; piston sizes available from Wiseco and the relative thickness of the cylinder casting and the powervalve design. For example the 2000-04 Honda CR125 can’t be converted to a 144 because the cylinder is very thin above the exhaust port. There are a lot of myths about big bores propagated by the dirt bike magazines, like 139s make more power than a 144. That’s bunk! Another funny myth is that a 144 piston is so heavy that your hands will vibrate off the handlebars and your engine’s crankshaft will shake apart. That’s baloney too! A 144cc piston is only less than 1 ounce heavier than a 124cc piston. These myths were started by a guy named Rick Petersen who used to run a business named RPM. He sold his company to Max Power and they specialize in making really expensive big bores, like 4-5 times more expensive than Eric’s kits. The biggest myth in the dirt bike business is that you have to spend $2,000 on a 125 to make it competitive with a 250F.

Who Rides 144s?

Eric Gorr invented the first 144 in 1976 for a customer who was bigger than average but still loved the handling of a 125. Since then 144s have become popular in off-road racing where 125 race with 200s. Pro mx racers used them illegally in 125 Supercross to get into the main event. In recent years the greatest demand is from 125 2-stroke racers trying to equalize against the 250F advantage.

Getting What You Pay For?

The old saying “you get what you pay for” implies that the more you spend the more you get. Not so in the motorcycle industry. Often times the people with the least experience charge the most money. Here’s an example; Max Power and PR2 have been doing big bores for 1/3 the time of Eric Gorr and charge as much as 3 times more! We can rebuild your entire engine for the less than the price that most of our competitors charge for a 144 cylinder alone! On the flip side of the cost equation is Kustom Kraft, Luke’s Racing, and Millenium technologies. They’re prices are 50 bucks lower than Eric’s but they don’t include real porting. Porting is the key to getting more power from a big bore kit, otherwise the engine produces more low end and just goes flat in the mid-range and actually produces less than stock.

Catalog Parts Not Custom! Cheap and Easy Everywhere.

We build kits using AMA approved Wiseco piston kits, which are available from Forward Motion, Wiseco dealers, Parts Unlimited dealers, or virtually any mail order motorcycle company. These are catalog commodity parts, not high priced frequently back-ordered custom pistons like our competitors use. Also our kits use stock or aftermarket replacement kits on the models that use head o-rings. Models like the Honda CRs and Kawasaki KXs use steel head gaskets and companies like Cometic and Moose Racing make oversized gaskets for the same price as stock. Our competitors use expensive spacer plates so you’re stuck buying replacements from them.

Warranty?

Although no new dirt bike comes with a warranty, Forward Motion has liberal policies regarding top end failures and warranties. However all the damaged parts and sometimes the engine must be submitted for evaluation. USC and FM developed a special program for people with our big bores that had problems beyond the scope of a normal warranty. The “Warranty Special” covers everything from normal wear and tear to dirt scratches from not oiling your filter, piston-seizure from not pre-mixing oil with the fuel, too-lean jetting, crashing, overheating from failed cooling systems, broken studs, cracks, powervalve breakage, and connecting rod failure. The cost is only $125 to repair the bore and you don’t even have to disassemble the powervalves. In fact we insist that you send us the complete top end so we can help you determine the root cause of the engine failure to fix it right the first time and save you money. We also offer free diamond honing ($25 value) of supermini and 144 cylinders for two years after you buy it. Nickel-Composite cylinder plating is so tough that in many cases, even when the piston seizes, we can clean it up with just honing!

Deluxe Engine Packages

You may consider choosing a bottom end rebuild along with a big bore kit. The average minicycle or 125 needs the bottom end rebuilt every two years or about every 80 engine hours. We offer engine rebuilding using American made fairly priced aftermarket products like Wiseco, Hot Rod, and Moose Racing. The basic bottom end rebuild service includes cleaning, inspection, polishing, and replacement of powertrain parts. Typical parts include a new crankshaft assembly, main bearings, all seals and gaskets. Optional parts include clutch baskets and plates, transmission bearings, gears, or shift forks. The basic price for parts and labor is $475 for late model Japanese minis and 125s. We also offer free installation of things like clutch baskets, reed valves, high flow waterpumps, flywheel weights, and lighting coils when you purchase the accessories from us. Sorry we don’t work on engine where you supply the parts. Call Eric for a quote on turnaround time and appointment

Special Offers with Big Bore Purchase

10% DISCOUNT FOR TWO OR MORE BIG BORE KIT ORDERS

If you can convince your friend or family member to send in their top end with yours, you’ll both save 10% That’s like getting a Supermini for $382 or a 144 for $449

FREE BOOK: Choose one with each Big Bore Kit

MX Performance ___ MX Riding ___ CRF ___ YZF ___ Motocross ___  ABC MX ___

We'll give you a FREE book with every big bore kit; just make your choice by checking the box on the Service Order Form.

Payment Methods

We accept bank checks, money orders, personal checks, business checks and give you free return ground UPS shipping for pre-paying with a check. We accept credit cards but only Visa and Mastercard, and that includes the debit cards issued by motorcycle manufacturers for contingency prize money. We prefer that you use PayPal and we’ll invoice you by email when your engine parts are ready for shipment.

We don’t accept UPS COD, IOUs, third party checks, post dated checks, food stamps, junk parts, promises of future winnings, family pets, or old lottery tickets.

Instructions on How to Ship Top Ends and Engines

For individual top end parts, send the complete cylinder, head, and powervalves all bolted together. Use a 8x8x8 inch box and plenty of tightly packed paper or styrofoam peanuts.

For Yamaha YZ and Suzuki RM models, send the whole engine because these models require crankcase clearance mods that can be performed with the bottom end assembled. Start by draining the oil, coolant, and fuel. Double-box the engine with at least a few inches of packing material between the engine and box and the inner box and the outer box. If you choose UPS, save the tracking number so you can track your package to see when it arrives. All orders are checked into the system in the week they arrive and turnaround time varies based on seasonality. In many cases we have several cores in stock for immediate trade-up.

How to Get the Ball Rolling

Click and Print the Service Order Form to send your engine parts in for service. Turnaround time is about two weeks and appointments are recommended for faster time. Email ericgorr@hotmail.com for an appointment based on your year, make, and model of your bike. If you need to talk to Eric you can call him on his cell phone at 1-630-825-5645.
2-Stroke Service Form

Transoceanic Fast-Track Service

We offer a FAST-TRACK SERVICE for customers living in Canada, Europe, Scandanavia, and Australasia. Plus we offer fast return on your new 144 kit with 4-day Global Express Mail service for the flat rate of only $30! We know how to handle the customs documentation so the taxman doesn’t overcharge you. Plus we offer discreet invoices emailed to you, and we can invoice your business or sponsors for tax advantages. We offer payment methods of Visa/Mastercard, bank wirements, and Paypal.

Also, there are no external markings, engravings, or embossments on our 144 cylinders, just a serial number that entitles you to a 1-year warranty on the Nickel-Composite plating. With the US Dollar at an all-time low against the Euro and the British Pound, this is a deal that you can’t get in Europe! Technical Notes: You can send a clean top end to us but not a complete engine by airmail. We supply photos and instructions for grinding the crankcases on Suzuki and Yamaha motorcycles. Just use the 2-Stroke Service Form and send your parts by airmail for the fastest turnaround time. International Service Form.

PRICES FOR ORIGINAL PARTS, TUNING, Nickel-Composite, & PISTON/GASKET KITS

These are complete spare kits that look original, un-marked

	PART NUMBERS	US$	EUROS
HONDA CR125 2005-07
Cylinder	12120-KSR-730	$352
Head	12201-KSR-730	$73
Valve set	14200-KSR-730	$165
Big Bore Machining & Nickel-Composite		$350
Wiseco 58mm, extra ring, & Gasket kit		$125
Total Price		$1,065	€852

 

	PART NUMBERS	US$	EUROS
HUSQVARNA CR/WR125s 2004-07
Cylinder		$420
Head		$100
Valve set		$200
Big Bore Machining & Nickel-Composite		$350
Wiseco 58mm, extra ring, & Gasket kit		$125
Total Price		$1,195	€885

     

	PART NUMBERS	US$	EUROS
SUZUKI RM125 2005-07
Cylinder	11200-36870	$471
Head	11111-36F11	$111
Valve Center	11250-3G6F40	$113
Big Bore Machining & Nickel-Composite		$350
Wiseco 58mm, extra ring, & Gasket kit		$125
Total Price		$1,170	€936

 

	PART NUMBERS	US$	EUROS
YAMAHA YZ125 2005-07
Cylinder	1C3-11311-01-00	$333
Head	1C3-11111-10-00	$92
Valve L	1C3-1131D-00-00	$153
Valve R	1C3-1132D-00-00	$153
Big Bore Machining & Nickel-Composite		$350
Wiseco 58mm, extra ring, & Gasket kit		$125
Total Price		$1,206	€988

How To Get The Ball Rolling

Click and Print the Service Order Form to send your engine parts in for service. Turnaround time is about two weeks and appointments are recommended for faster time. Email ericgorr@hotmail.com for an appointment based on your year, make, and model of your bike. If you need to talk to Eric you can call him on his cell phone at 1-630-825-5645

Service Order Form - Fill out and Print this form from your web browser

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