Spears Racing’s specialty is racing engines and road racing motorcycles for all lightweight motorcycles, but Spears Racing also offers a variety of services from full turn-key racing preparation to race management of your team to running your race engine program. . We also offer suspension enhancements from aftermarket cartridge kits,piston/valving kits and replacement rear shocks for racing and track day participants.

“Our passion is competing, Our goal is to win”

From the Dealership to the Race Track

The Day of Purchase

The day of purchase,right side

all of the bodywork is removed time to start the build

Stock foot peg assembly, stock rear set and stock rear brake reservoir

Stock Mount and Ohlins Rear Shock

All body work removed and ready to start the build

OEM location of rectifier/regulator.Mounted onto the left side of the fairing stay, this will get wiped out in a crash.

Rectifier/Regulator removed and will be re-located


New location of the Rectifier/Regulator

Rectifier/Regulator relocated with the Spears Racing re-locator unit.

Close up of Rectifier/Regulator relocated with the Spears Racing re-locator unit.

Removed Pair valve unit , install Spears Racing Block off Plate

Close up of Block off plate installed

MWR Race Installed

High Pressure Radiator cap installed,will allow the engine to run cooler

Harness relocated for the Voltage rectifier /regulator, it needs to be pulled back from the fairing stay

Triple clamp is off and time to remove the ignition switch assembly

Center punched and drilled the safety screw heads off to remove the ignition switch

Switch removed, a little heat and these screws will twist out fairly easy.

Spears Racing Steering Stop installed

Close up of Steering Stop

Close up of Steering Stop

Clutch Assist Return Spring

HM Plus Quickshifter Installed

HM Plus Close Up

HM Plus sensor install,makes it real sooth on all up shifts

HM Plus Close Up

HM Plus display up close , makes all of the adjustments simple

Spears Racing Patented Shock Variable Shock Mount

Spears Racing Patented Shock Variable Shock Mount

Lacomoto Superbike seat support

Spears Racing Switch bypass ignition,Rev 2 ,+2.5 Clip ons,Ohlins Cartridges

Spark Exhaust system Titanium can,Aluminum Spears Exhaust Bracket,Rear Master Cylinder Reservoir Delete kit

Galfer Brake Full Floating Brake Rotor, Spears Racing Superbike Front Brake line

Left Side Lacomoto Body kit (weighs 6 Lbs for complete kit) Pre Drilled,fasteners included

415 Drive Chain kit (lightest rear 415 rear sprocket),Aluminum Spools,Shark Tooth,Rear Sets,

Right Side Front Lacomoto, Galfer Full Floating rotor,Superbike brake line,Spears Levers ,Spears Lever Guards

Left Side Lacomoto. 2.5 Clip ons ,Spears Adjustable levers,Spears Lever guards

Spears Racing Levers,Spears Racing Superbike Brake line

Your view

Your view

Left Side of competed bike

2018 Kawasaki Ninja EX400 Spears Racing Build

Heat Treatment & Cryogenics

Descriptions of stress with your parts:

During the process of manufacturing, production and the machining phases on a molecular level materials are subject to strenuous events. These events cause molecular displacement or gaps in the matrix during the solidification stages. these gaps are out of place molecules which, are not working in uniform with one another but, are displaced and can be working against each other. This causes a lack of strength and durability placing a great amount of stress on the newly formed objects.

Textural Stress – Arises due to microscopic inhomogeneties in a metal.

Body stress – Stress created or produced by an external load and contingent body stress when the load is removed.

Residual Stress – The remains after a load is removed and clearly seen as the retention of stress cracks. It is impossible to cold work steel without creating stresses on the metal. Most common major stress is caused in machining or altering the parts by any form of metal removal. Grinding can produce temperatures in excess of 1650°F. This produces great amount of surface stress.

Conventional Heat Treatment & Tempering:

Heat treated parts go through extreme amounts of stress inducing phases. Consider taking a bar of steel that has been heated to 1472°F for an extended period so the temperature is even throughout the metal then, plunging that steel into water that is 68°F. the rapid cooling reduces the surface temperature almost instantaneously while the interior of the structured metal is still red hot. Although, the heat does dissipate, it does not dissipate uniformly. Therefore, the radical cooling of the outer core and inner core in a non-uniform way causes compression stresses which, need to be stabilized.

The part now needs to be tempered to stabilize the newly formed martensite. If this is not completed, the inherent stresses are arranged to cause the part to crack or explode. Because such high temperatures are needed to relieve stress, more austenite grain structures are transformed from martensite, creating yet, another stress layer.

The best and most complete way to remove built up stresses from heat treating and manufacturing is through the use of cryogenic temperatures Metal Treatment. a properly performed deep cryogenic treatment will ensure stress relief. This process will never change the color of the metal in any way, as it will change with standard heat treatment.

The engine building process is an extremely critical part of building a bike:

Stocked facility and fast build times

We control the full build process, not only with how the machining process is done but also with how quick we can have an engine completed. We have an average build time of 14 to 21 days! This will depend on the current work load (engines in Front of yours), but we keep all OEM and aftermarket in stock at our facility, CP-Carrillo Rods and Pistons, Kawasaki, Suzuki and Yamaha OEM Parts to meet the demand of most customers.


Spears Racing will completely inspect all of the working components of the engine:
The top end will be torn down and careful measurement of the piston to head (squish) must be taken to avoid collision of the moving parts and the cylinder heads will be completely inspected. Increasing the compression ratio of an engine by machining the gasket surface of the cylinder head is where most of an engine’s power increase comes from.

Compression ratios can also be increased by machining the engine cylinder deck or changing the thickness of the head gasket or a combination of the aforementioned, Spears Racing has designed several different pistons for all of the lightweight engines that often are a great fit.

Spears Racing offers several types of head work to match your needs. First there is a STANDARD valve job, which machines the valves and seat area of the head exactly to the manufacturers required specifications. Second there is the competitive valve job (Referred to a SUPERSPORT Style) the valve faces and stems are machined, and the intake valves are given a special double cut. The exhaust seats are given a three angle cut. The intake seats receive a blended four angle cut or full radius cut depending on the application. Finally all valves are hand lapped and checked for correct sealing. All of the seat work is done on our state-of-the-art valve machine. Once the cylinder head has been machined and thoroughly cleaned, it is time for reassembly. Careful assembly of the cylinder head involves checking valve spring height and pressures as well as setting the valve lash for proper clearance.


For those not wishing to radically modify the ports, port irregularities and casting lumps (called flashings) are removed. The critical area of valve-seat-to-port is blended and the junction of the carburetor-adapter to-manifold is also matched and blended, the complete port and combustion chamber reshaping, the area is shaped and contoured to maximum flow and while maintaining flow velocity for power increases throughout the RPM range.

Lower End:

The Lower end is disassembled after the cylinder head has been removed from the engine. While the factories do a fine job on assembly, they leave a few small details to be taken care of. Oil clearances can be carefully set at a higher clearance and checked with Plastic gauge, oil pumps can be modified and things like ceramic transmission bearings and Cyroing and Micro-Polishing can be done to “free up” inertial and frictional power losses.

Other modifications on the bottom end can include bead blasting piston crowns, checking piston to cylinder wall clearances and changing/setting if necessary, oil pump and oil pressure relief valve modification for changing pressure output and transmission modifications. The cylinders will be installed and the proper deck height will be obtained to give the best reliable power and torque. Next are the cylinder head(s) – a process that only Spears does. The heads are bolted to the cylinders and are CC’d to find out the current compression ratio. After this is completed, the heads are ready for there finial assembly to the cylinders. The transmission will be clearanced in the cases and new transmission carrier bearings will be installed if needed (upgrade to Ceramic). The crankshaft will be magnafluxed to ensure that it has no cracks at the time of installation and this too will be clearanced in the cases for the correct clearances. The connecting rods will also be clearanced at this time. If an upgrade is wanted, we suggest the Carrillo connecting rods. The cases will be prepped with new main crankshaft bearings as well. After final inspection, the Spears crank case defuser (depending on the engine type) and the cases will be closed up. While the cylinder head is disassembled and being machined, it is recommended to have a valve job performed to give the valve seat better flow and sealing characteristics.

Degreeing camshafts:

Camshaft timing is so critical on a sport twin (see our cam timing article), there cannot be any deviation between the front and the back cylinder opening and closing numbers (you’re only going to be as strong as the weakest cylinder).After the final cam timing numbers are obtained, the cams will be pulled for the final time and the sprocket carriers will be welded to the camshaft bodies (to ensure no movement of the holder) and reinstalled. The engine will be closed up and be ready to ship.

A complete review of the work, Pictures and all of the documents are part of this and will be given to the owner.

Finding the Right Machine Shop for You

Not all machine shops are the same just as not all engine builds are the same. When selecting a machine shop, the engine builder should consider the things that are most important. If you are looking for a quick turn around time, a close machine shop that has less of a back log is probably a better selection or deserves more consideration in the selection process. A machine shop that has less of a back log in work deserves a little more investigation. Don’t automatically assume that a shop that is less busy than others in the local area does bad work. The shop may be newer and has not built it’s reputation yet. Most machine shops do very little advertising and rely on word of mouth advertising between racers to help their business.

Suzuki SV650 Ported Head

Kawasaki EX Ported Head

Before/After Ported Head

Supersport Valve Job

Suzuki SV650cc Superbike Winning Engine Build

Kawasaki EX315cc Winning Engine Build

Micro Polishing is one of the best things you can do to improve your transmission! Micro Polishing very gently polishes and smooths your gears and removes metal stresses uniformly. This procedure in scientific term is called “Isotropic” Micro Polishing is a surface treatment for ferrous (steel) parts that will reduce friction, increase durability, and increased effective film thickness (lubrication)It gently polishes the gears faces and dogs in the contact zones, reducing friction, and frictional losses. That means less heat, better fuel economy, and longer life. Micro Polishing will not make your gears stronger (just the surface), but reduced friction means reduced stress which equals better durability under demanding conditions!

Less inertia = Less friction = MORE POWER = Less fuel consumed The surface is asperity free, with a on directional (isotropic) texture. The surface has increased bearing ratio and enhancing the lubricant retention properties of the mating surface. The parts will have considerable amount of less friction, promoting less heat and wear.

The benefits are:

  • Freeing up lost horsepower
  • Less heat
  • Longer service life
  • Smoother movement
  • Smoother shifting

The process will pay for itself due to longer service life and less part replacement.


In engines and transmission assemblies, moving parts rarely touch each other. The crankshaft in an engine does not technically contact the main bearing surfaces, only a thin oil film separates the two surfaces. In essence that is in fact what oils designed function, the of use lubricants prevents parts from actually touching. In understanding that… if things don’t touch, where does the friction come from? Take for example transmission gears. As machined from the factory, gear surfaces carry characteristics of fine flaws of very small “peaks and valleys”. In the rotation of the moving parts, the gear oil is forced out from between the gear surfaces. As the oil is pushed out, a fine amount of turbulence is created as the oil has to find its way through those “peaks & valleys”. This turbulence causes the oil to work in contrast, resulting in friction raising the temperature of the gear oil.


When it comes to machined parts, smoother is better. However even the most scrutinized machined parts are still plagued by “peaks & valleys” Turned, ground and even lapped surfaces all create some degree of turbulence and increased heat. Standing to reason that any process that removes those peaks will reduce the heat and friction.


So how is a “peak-free” surface obtained, that doesn’t change the size of the parts? Utilizing proprietary technology we can produce a finer quality of work in short spans of time, than others

As a lot of the current racers and a few of the new racers know that the little bikes do have issues with their transmission popping out of gear, we are hearing more and more from the racers that they are in the top end of 5th gear and it will just pop back into 4th with no warning. Always remember these motorcycles are built as a commuter low budget bike that we, you want to take to the next level.

Spears Racing has been doing undercut transmissions for decades and decided to specialize in the Kawasaki EX400,Kawasaki EX300/EX250 and the Yamaha FZ/MT07/R7/ R-3 transmissions with what we call the “Race Cut” this is essentially our way of doing the process of undercutting Transmissions( in the engagement direction only)

Once the undercutting process has been achieved, we then begin to work within the particular application to complete by blasting all of the transmission gears to maximize the surface area for cleanliness and inspect that the gears spacers, washers are ready to assemble back onto the shafts.

Undercutting is one of the most highly regarded modifications for race motorcycles. Many manufacturers do not undercut their transmissions at the factory. Undercutting involves the modification of the drive dogs and slotting to precise angles. Creating an interlock of the gears under acceleration, virtually eliminating the occurrence of an involuntary gear jump. Most drive dogs from the factory posses a ZERO “Rounded” degree back cut, producing rounded gear corners under normal wear, in turn creating involuntary disengagement. Spears Racing’s under-cutting service can precision cut your transmission to perform at its most accurate and true level of performance.

Exchange Service Available