Karting Technical Tips Karting Technical Tips Karting Technical Tips Karting Technical Tips Karting Technical Tips Karting Technical Tips Karting Technical Tips Karting Technical Tips

Tech Tuesday: Wet Chassis Set-Up

Leaning to the outside while negotiating a bend helps increase the grip of the outside tyres

Some drivers love racing in the wet, others hate it. But it is also true that liking or disliking the wet depends a lot on what performance one has in these track conditions. Kart set-up is extremely important in wet weather and driving itself changes completely. Wet conditions set-up The main critical aspect of wet conditions is the extremely low grip of all four tyres. This leads to understeer entering bends and oversteer exiting them, with really low traction. Also braking becomes extremely difficult with frequent locking of the rear wheels. To help reduce all these effects, which persist even when rain tyres are fitted, we must really work on kart chassis set-up. First of all we must balance the chassis to give maximum front grip and maximum rear grip! A narrow rear end increases rear grip as does a wide front end for front grip. The front end can be be made really wide by fitting long front hubs. Now work on the front angles. Caster should be increased to the maximum so it gives incidence to the front tyres when entering a bend and reduces understeer. Camber should be set to zero with the driver sat in the kart. Finally, some toe-out gives some advantage. Sometimes, especially with not very tall drivers, it is important to lift the seat to raise the centre of gravity.

Edgar's Hyundri Super One MSA Series, MSA, KF2, PFI, RSF, Ben Barnicoat, ART.
Love it or Loathe it, At some point it’s going to rain, the right set up makes the world of difference.

This creates a greater momentum when running along a bend which helps increase grip on the outside tyres. Of course if you have to add weight to reach the minimum weight limit then add it as high as possible on the kart seat. Seat stays should be loosened to give more flexibility to the chassis and a stiff rear axle fitted. This last solution though, in my opinion, gives little advantage, since the speed and grip of the chassis are so low in wet track conditions that the forces acting on the chassis are also reduced. This means that the chassis flexes very little and the rear axle may not flex at all. As in dry track conditions, tyres are very important. Pressures should be much higher than for slicks on a dry track since in the latter conditions the tyres heat up much more. Be careful though that, when using rain tyres, all the tyre print is touching the ground and not just the centre section. You can check that after your first run. If you only run on the centre then the tyres won’t last as long and grip will of course be reduced. How to drive in wet track conditions As we have already started to see, in wet track conditions one important thing is to put a lot of load on the outside tyres, front and rear. This can be done by even eliminating some load from the inside tyres. So when driving in wet conditions the position of the driver’s body is extremely important. To give as much grip as possible always lean towards the side where you want to increase the grip. So when running along a bend lean to the outside.

Go on slicks they said…

An even more sophisticated movement of the body is to lean to the outside and towards the front when entering the bend and then lean backwards towards the outer rear tyre when exiting the bend. This will help reduce understeer entering the bend and also reduce the oversteer exiting it. Another important factor to consider is that in wet conditions it is much better to brake earlier and concentrate on the exit of the bend. Locking the wheels when braking can make you lose control, time and spin. Also, in general, never accelerate with the front wheels turned. Accelerate only when the front tyres are straight and parallel to rear tyres, or almost so. The most important thing though is to drive the kart on completely different lines from those used when track is dry. When the rubber laid down on on the track becomes wet it becomes extremely slippery so it is much better to find grip on wet but clean tarmac. The best line to follow is to run the bend all the way round the outside where rubber has not been deposited. In some bends another possibility is to go out wide when entering the bend and then to cut in to the inside. Finally, to help comfort and concentration, it is a good idea to buy a wet suit to keep your body dry and warm. All these points are just a start, you must gain experience of driving in these conditions and fine tune your kart’s set-up to optimise performance.


Like this article? Then read more Tech Tuesday here:

Tech Tuesday – Terry Fullerton’s 7 ways to improve Karting

Tech Tuesday – Axles

Karting Technical Tips Karting Technical Tips Karting Technical Tips Karting Technical Tips Karting Technical Tips Karting Technical Tips Karting Technical Tips Karting Technical Tips

Tech Tuesday: Kart Aerodynamics

An aspect often not estimated is the aerodynamic factor acting on a kart chassis and its driver. Since a tenth of a second is vital for a kart driver to win, we must consider that on particularly fast tracks and even more for fast 125 cc shifter gear chassis high speeds generate an important resistance of air on the kart. This is determined by the laws of physics that show how resistance to penetration in air is proportional to speed if such speed is minor to 100 km/m, but changes to a proportion to the square of speed for values over 100 km/h. Many kart chassis constructors are in fact now projecting front and side plastic bumpers also looking at good aerodynamic penetration.

No, not that kind of areodynamics…

Aerodynamics on chassis

A kart with its driver has a very bad CX factor, which is the coefficient of aerodynamic penetration. This aspect, even though front area of kart and driver is limited, is determined by the total absence of front cover to driver and kart and by the turbulence that is generated behind the driver who represents nearly 45% of the front area of the entire system. So, for a start, a more compact position or maybe having the driver slightly lied down can give significant improvement to aerodynamic penetration and so also to performance.

Lateral bumpers

Side protections already give good effect since they cover rear tyres reducing turbulence and increasing penetration. So when widening rear carriage see if tyres are still sufficiently covered. Some companies like Tecno have studied both side and front bumpers to optimize fresh air flow towards the radiator obtaining better engine cooling.

The OTK M6 Bodywork was designed with areodynamics in mind due it its slippery profile

Front bumper

It has the function of course of  protecting from front collisions with other drivers or obstacles, but has also a good aerodynamic effect. First of all to work well the spoiler must be kept as low as possible to reduce turbulence of the air passing under the chassis. Such turbulence in fact would slow down the passing air which would “stick” to the chassis reducing its speed.

The air moving over the front bumper makes it work like a spoiler pushing it down and increasing front grip. Over 100 km/h such vertical force can be equal to 4 kg, but really under such speed the effect is limited, and becomes secondary respect to aerodynamic penetration.

Working in such way on the front bumper gives only positive effects: better aerodynamic penetration and small increase in front grip.

Base protection

Base protection is used to position the driver’s feet and to protect him from eventual stones coming from the track. The three surfaces of the front spoiler, the base protection and the inferior surface of the seat make a continuous surface. They must for this reason be on the same level so that any edge is avoided and air flow is free to pass smoothly under the kart. Some technicians say that a ground effect can be obtained on fast tracks curving slightly the base protection, but such work seems to be too complicated compared to the result.

PFPK1605GX160 -147
The ‘Big Nosed’ Prokarts have a large Nassau panel to divert air away from the drivers’ un-areodynamic legs

The driver

The driver has really, as already anticipated, a bad aerodynamic penetration. Feet and legs will direct air flow towards the chest of the driver and slow down the kart, or laterally if well positioned. The front number plate help to limit such effect and will have to be as wide as possible to cover the driver and also will have to be well positioned to connect itself to the legs.

The arms of the driver will have to be positioned well in contact with the body only moving the forearm to turn the steering wheel. This will also help a better aerodynamic penetration. An additional effect is that this position will send air flow towards the engine or radiator helping engine cooling.

Finally it is clear that small drivers (once more) are helped on an aerodynamic point of view. I have myself seen on the Parma track in Italy tall drivers loosing much of their advantage on the three long straights of the track.

Head down, Alfie Brookes tries to gap the field in the Honda Clubman class. - edit


With shifter gears kart it can be quite simple to see the effect of aerodynamic penetration by reaching a certain speed on a straight and pulling the clutch suddenly. The kart will go on running along and we can measure the speed of the kart (we must have a telemetry system that measures speed with a sensor on front wheels) after a certain number of metres (300 for example). Try this test with different configurations of the kart bumpers and driver positions. Of course testing must be done with exactly the same track conditions (possibly the same day) and no wind. If wind or grip of the track change results will be completely unusable since the effect of these two parameters are similar to the aerodynamic resistance.

Like this article? Then read more Tech Tuesday here:

Tech Tuesday – Honda GX200 vs. Gx160

Tech Tuesday – 7 things to check on your kart

Karting Technical Tips Karting Technical Tips Karting Technical Tips Karting Technical Tips Karting Technical Tips Karting Technical Tips Karting Technical Tips Karting Technical Tips

Tech Tuesday: Weight And Seat Positioning

Even though many parameters determine the grip on each tire, everything is finally led to the vertical force acting on each wheel. The greater such downward force is and the more the grip between the tire and the asphalt.


Centre of gravity

The centre of gravity is the point of a system (chassis plus engine plus driver) where one can consider all the weight concentrated. Once we define this in a kart, and generally such point is positioned in the stomach of the driver, we can calculate all the forces acting on the kart concentrated in the center of gravity. For example the weight of the kart can be concentrated in the centre of gravity as the sum of all vertical forces when the chassis is not moving (weights multiplied by the gravity acceleration). We will call “a” the longitudinal distance between the centre of gravity and the front carriage, and “b” the distance from the centre of gravity and the rear carriage. So we will be able to say, following the laws of the physical equilibrium, that the vertical forces acting on respectively on the rear tires (Fp) and the front tires (Ff) will be equal to:

Fp = Pvehicle * (a + b)/b,

Ff = Pvehicle * (a + b)/a,

where Pvehicle is the total weight of the kart (chassis, engine and driver) and:

Ff + Fp = Pvehicle.

We are making an approximation considering the weight of the kart a force.

Leaning can als help you look cooler, not just distribute weight…

Effects of weight distribution variation

So the variation of the position of the seat of the chassis along the longitudinal length of the kart varies the parameters “a” and “b”, which means that also weight distribution of the kart varies between front and rear tires. Generally the longitudinal movement of the seat has a maximum value of around 4-5 cm, but a few centimetres determine great differences in weight distribution. For example the distance between front and rear carriage is generally in karts around 104 cm. With front weight equal to 40% and rear equal to 60% the centre of gravity is 41.6 cm from the rear axle and 61.4 cm from front carriage. If we move the seat 2 cm to the front of the chassis distribution will be 42% on front tires and 58% on rear tires. Such variation of 4% of the weight could appear a small quantity, but can really determine great difference in kart performance. If we move the seat of the chassis towards the front carriage the vertical force on front tires will increase and the force on rear tires will decrease. This will automatically determine an increase of front tire grip and a reduction of rear tire grip. So moving the seat to the front increases oversteer and moving it to the back increases understeer. The variation of the two parameters “a” and “b” will not vary directly shifting the seat. In fact the movement of the seat will determine a movement “c” of the centre of gravity as follows:

c = Pdriver/Pvehicle*x,

where “x” is the movement of the seat.

So it is extremely simple to setup the basic grip on the four wheels just by the right longitudinal positioning of the seat of the chassis. After such positioning the other parameters of the chassis will vary the forces on the four wheels for fine tuning.

leaning too much can also hinder your driving…

Generally weight distribution must be regulated to have 60% of the weight on the rear tires and 40% on front tires. It is also true that every chassis has its own particular regulations for what concerns weight distribution. Ask your chassis builder or shop for the right values of weight distribution between front and rear tires. Such parameter is really too important to be mistaken. In addition to this we must consider that weight distribution should be equal between right and left tires on the front and on the rear. Because of the engine positioned on the right hand side, the seat will be slightly shifted to the left hand side of the chassis. This is of great importance especially when braking before a curve, since the balance of the chassis will be perfect, and the kart more stable in such phase, only if left and right wheels will have the same grip acting on them and the centre of gravity will be in a central position respect to the wheels.

Also the driver, especially in wet track conditions, can move inside the seat and vary weight distribution. For example moving your body forward when entering a corner helps front grip, and moving the body backwards when exiting a corner helps traction. This, also thanks to lower speed of the kart, has great effect on wet track conditions.

Next issue we will proceed consider weight distribution on the four wheels varying centre of gravity height, which will also determine great effects when running along a curve.

Like this article? Then read more Tech Tuesday here:

Tech Tuesday – How to read your tyres

Tech Tuesday – 10 ways to get the best performance in TKM

Karting Technical Tips Karting Technical Tips Karting Technical Tips Karting Technical Tips Karting Technical Tips Karting Technical Tips Karting Technical Tips Karting Technical Tips

Tech Tuesday: Rear axle choice

The Rear axle is one of the main elements to influence chassis setup. The stiffness of the axle determines behaviour of rear part of the chassis, making the kart oversteer or understeer, and changes strongly the balances of forces acting on the chassis.

1As we know in fact kart behaviour along a curve is based on the possibility for the internal tire to lift off the ground since there is not differential system on rear axle. Now a softer axle bends more and quicker than a stiff one. This means that a kart can reduce grip on rear tires, and increase oversteer with a softer rear axle and vice versa with a stiff one. Very simply, but always considering there must be a balance in kart setup between front and rear stiffness, increasing rear axle hardness gives better grip on rear tires, but difficulty in entering curves, because of too high grip on rear tires compared to front tires. The opposite happens having softer axles.

But which are the parameters that vary rear axle stiffness? They are three, material, thickness of tube wall, diameter of the tube. Along the years chassis have shifted from having full tubes of small diameters (25 mm) to having hallow tubes as rear axles with increasing diameters from 30 mm, to 40 mm, and in recent days to 50 mm. What happens is that a tube which bends with an elastic deformation returns to its initial straight form after the kart exits the curve. This return to initial shape can happen with different speed and promptness.  A stiffer axle is quicker in returning to its straight shape, and this determines faster reaction of the kart in having the internal tire back on the ground when exiting the curve. The two rear tires touching the ground give more grip and the possibility to accelerate after the curve. So material of the rear axle determines different setup of the kart. Some materials are surely better then others in their elastic capacity to regain initial straight shape. Much effort is being done by kart constructors to find materials with better elastic characteristics. Thickness of the tube also acts on axle stiffness R with the following formula:

The material, wall thickness and diameter of an axle all affect set-up

R is proportional to: a * (d22 – d12), where d2 is the Bigger diameter axle gives surely a better look to the chassis. But the practical difference is that for physical reasons, which we will not go deep into, a bigger diameter axle is more reactive than a smaller diameter one. So the shift to larger diameter axles has had the aim of increasing reaction of the chassis exiting curves and giving the possibility of accelerating earlier.

But it is not only stiffness of the axle to act and change setup. We know that rear carriage width also acts on rear tire grip. The wider the carriage, the lower the grip. First of all this is due to the fact that a longer rear axle, and a wider spacing between rear tires, permits greater deformation and bending of rear axle along curves. It is somehow equivalent to having a softer tube. On the other hand another effect is that rear carriage width increase makes the rear tires lift with more difficulty. Rear carriage is flatter on the ground and even though rear grip decreases, eventual sliding of rear tires is smooth and uniform, easily controllable. If we reduce rear carriage width rear axle becomes stiffer, grip increases, but rear carriage is less stable. Internal tire lifts without rear axle bending much. What happens is that external rear tire blocks itself laterally on the ground instead of sliding. But as soon as lateral force is too strong rear external tire suddenly looses grip along the curve, with fast lateral slides of the rear of the kart, which becomes much more nervous and difficult to control. With high drivers this effect is even more evident since centre of gravity is positioned higher and momentum on kart increases. That is why high kart drivers usually tend to have wider rear and front carriages.

Finally now we know which parameters act on rear axle stiffness, amongst these usually the type of material is indicated by a lettering on carved on the axle. Also we know how stiffness acts on kart setup. Finally we also have seen that rear carriage width acts on rear axle flexibility and on general chassis behaviour along a curve.

Like this article? Then read more Tech Tuesday here:

Tech Tuesday – Terry Fullerton’s 7 ways to improve Karting

Tech Tuesday – Best helmets under £350

Karting Technical Tips Karting Technical Tips Karting Technical Tips Karting Technical Tips Karting Technical Tips Karting Technical Tips Karting Technical Tips Karting Technical Tips

Tech Tuesday: Choosing the right Karting seat

The seat and its supports are often underestimated by chassis tuners and drivers, but on the contrary such elements are a fundamental part of the chassis and determine a lot of the stiffness characteristics of karts.

Seats come in many different brands, stiffnesses and materials, Giving each one unique characteristics

Various seats and supports

The structure of the seat and its connections to the chassis generate a system which varies sensibly the chassis stiffness. Moreover the material of the seat can vary and so also the stiffness can vary. Glass fibre, Kevlar, carbon or mixtures of these elements, with also different thicknesses of the layers, can generate variations in the torsional flexibility of the chassis in its rear part, since the seat itself will change its stiffness.

For example a carbon fibre seat is, with the same thickness, three times as stiff compared to a glass fibre one. A Kevlar seat is on the other hand much more elastic if compared to a glass fibre one. Costs are also to be considered and, as usual, carbon fibre seats cost at least double a glass fibre one.

With the use of supports it is possible to preload the chassis on one or both sides. Such load will be positioned on the rear axle bearings. Such preload will be obtained by using length of supports of just a few mm superior to the distance between the holes in the seat, where the support is screwed, and the lateral axle bearings. Supports can be bent and twisted together to obtain something very similar to a spring. Straight supports are extremely stiff. In fact a straight support works in compression on the rear axle where it is linked. Such supports are very stiff in compression. On the other hand the same support bent, works in flexion, so has a much higher elasticity and, as said before, works well as a spring, deforming when a sudden bump is hit by a rear tyre, but still creates downward force when it is needed to increase rear grip.

World's biggest kart seat T7 OMG
Proof that your dad can have a go in your kart, the “I won’t fit” excuse just wont cut it here…

Effects of supports on chassis behaviour

The stiffer the seat and its supports and the faster will be the diagonal load transfer to the wheels. In fact the weight of the driver whose effect is also increased by the centrifugal lateral force when running along a bend, is transferred to the rear tyres through the seat and its supports. If no supports are present the chassis will first bend and then only part of the weight will transfer to the rear tyres.

Usually it is best for better performance and faster reaction of the kart to have a quick weight transfer, which means good seat and supports stiffness. On the other hand a very stiff seat and supports system does not absorb any irregularity of track surface. We must not forget that if initially caster of the front internal tyre transfers load to the rear external tyre, it gives back load to front wheels as soon as it is the only rear tyre that touches the ground.

The stiffness of seat and supports permits the rear part of the chassis not to flex too much, so we will have a good lift of the internal rear tyre during a curve. If the chassis bends too much instead, both rear tyres will keep touching the ground generating great under-steer.

Even when youve done with your seat they can be useful

On the right side of the chassis under the seat we always have two tubes, that are not only connected by the welded tubes, but also by the engine mounts. This determines the fact that the right side of the chassis is stiffer then the left one.

Acting on the seat supports we balance stiffness on the softer left side. If we use an old softened seat, with holes too big for the screws, we will have a low performance chassis. There is nothing worse then a chassis with its seat moving all around. It is also useless to try to set up the chassis with all sorts of regulations, if the area where most of the weight is concentrated deforms easily in any direction.

It is for this reason extremely important to well fix the seat to the chassis with well dimensioned holes, possibly hardened by metal rings, maybe glued to the seat with some resin.

Only when grip is extremely low (dirty or wet tracks) we can use rubber rings that absorb all the forces without loosing connection between the seat and its supports. The best solution, even though more complex, is to have the correct seat for different track conditions. Also some sponge can be used to increase comfort, but with no excess, otherwise we would loose the feeling between our body and the seat-chassis. In fact it is always with your “bottom” that you feel your chassis and understand how to drive it.


Like this article? Then read more Tech Tuesday here:

Tech Tuesday – Pistons

Tech Tuesday – Welding

Karting Technical Tips Karting Technical Tips Karting Technical Tips Karting Technical Tips Karting Technical Tips Karting Technical Tips Karting Technical Tips Karting Technical Tips

Tech Tuesday: Welding Part

Karts are made of steel tubes with different compositions of Carbon, Nickel, Chrome and Vanadium. Such tubes have particular characteristics that determine the functioning of the chassis. Elasticity of the material, diameter of the tubes and thickness of tube walls determine the capacity of the chassis to bend, absorb bumps in the track and generate vertical forces on tyres as to create downward forces that are the base for grip generation between tyre tread and asphalt. All these situations are possible only because steel tubes are linked together in a certain way. This “way” is welding of the tubes one to the other.

A welder doing his thing

What is a welding?

A welding is a volume of material that has been fused and solidified by the heating with different systems of a volume of material. This volume usually is composed by the sum of parts of two different elements that have to be joined one to the other and some additional material added and mixed with the two parts. In karting weldings are used for unifying together the tubes of the chassis and positioning parts such as rear axle bearing mounts. The way the weldings are realized determines much of the quality of the chassis in terms of resistance, flexibility and deformation.

Kart chassis are welded using a welding machine that creates a high tension between a cathode and an anode and, through the passage of energy between the two, generates very high temperatures. This high temperature melts the metal of an electrode and of the tubes of the chassis. These metals mix and solidify together creating a unique metallic element that links the tubes together.

These electrodes are made of iron or, for better quality, of steel. Finally the welded parts will show an area of melted and solidified material that, in ideal conditions and perfect welding procedure, will have almost the same strength and characteristics of the tubes themselves. In reality though, air and high temperature determine oxidation of melted metals and change in the microscopical structure of metals. This can bring to weakness of the welding.

An example of where you may need to welf your chassis, though this one might be a write off!

Welding machine and process

A welding machine has the capacity of generating a tension between two electric lines that end one with a clamp, that has to be positioned on the chassis, and one with a changeable electrode that is mounted on a second clamp held by the welder. The welding machine has a scale that regulates the tension between the clamp, and the chassis to which the clamp is linked, and the electrode. When this element is positioned close to the clamp and/or the chassis the high tension between the two elements creates a passage of electricity and the creation of great heat between the parts even though they are not touching each other. The greater the tension regulated on the machine and the earlier and with greater distance between the two elements we will have a passage of electricity and the melting of both the electrode and the area of contact between the electrode and the chassis. This will lead to a fusion between the metal of the tubes in contact and the material from the electrode.

Welding is a complicated process that gives good results only if the welder has the capacity and experience to obtain the right fusion and melting of material from the electrode and the tubes. In fact if tension is regulated too weak no melting effect will be generated and we will only obtain a continuous and repetitive sticking of the electrode to the tubes with difficulty to take it off once it is stuck. On the other hand a too strong tension will determine an excessive fusion of material with holing of the tubes and weakening of the entire structure. The choice of tension must be done based on the thickness of the electrode and the thickness of the elements joint together (walls of the tubes).

The welding done by the welder manually usually is completed in more phases. After each weld, along the line of contact of the two tubes, the area, that has partially cooled down and from an orange-red colour given by incandescence has become grey, must be checked to see what material has really generated a good and strong link of the tubes, and which is instead only laid over the tubes and has no real joining effect. The first “good” weld shows a silver shiny area, the second is mainly a grey unsmooth surface. Best check is made by hitting hard the welded area with a metal hammer and a metallic brush (often given with the welding machine as kit, together with eye protector glasses). If the material is correctly hardened it will not come off even with the hardest hammering you can do, otherwise metal parts will come off, which means they would not anyway resist more then a few minutes when the kart is running and bending.

A kart chassis can be complex and highly strung

Practical welding hints

Let us see how to proceed when welding two parts of a chassis. First of all be sure to position and fix well the two parts that need to be joint together. The surfaces that are in touch must be in good contact and well blocked. Then position the clamp on one of the two parts. Be sure the clamp is in good contact with the metal. If the clamp is positioned on a chassis tube verify that paint does not isolate the chassis from the clamp, in fact there must be contact metal to metal to obtain tension transmission to the area that must be welded.

Now try to set voltage on the welding machine starting from a low value, usually indicated on the instruction sheet of the machine depending on the thickness of the electrode used. To warm up the electrode touch quickly the clamp that is surely the element with better tension transmission compared to the chassis of the kart. After the electrode has lit up producing some sparks it is ready for welding. Always cover eyes with welding mask or glasses!!! This secures from sparks in the eyes and even the strong light coming from the lit electrode must be absolutely avoided since it can harm seriously your eyes and anyway partly blinds you for some time.

Start touching quickly the area to be welded and see if sparks are produced. The quickness in doing this is motivated by the fact that if the movement is too slow the electrode sticks to the metal tubes and is very difficult to pull off. The real welding must be done positioning the electrode at a certain distance from the area that has to be treated. Also the electrode must not be vertical respect to the surface to be welded, but inclined. This should permit a continuous movement of the electrode on the surface with production of a strong light and no sticking of the electrode to the metal. If this does not occur and the electrode goes on sticking to the metal we can try to increase the tension on the welding machine and this will help avoid the problem. After each weld hit hard the area with a metal hummer so all the waist material comes off and leaves a good clean surface on which to work on.

Like this article? Then read more Tech Tuesday here:

Tech Tuesday – Pistons

Tech Tuesday – Weight and seat positioning

Features Features Features Features Features Features Features Features

Tech Tuesday: Honda GX200 vs GX160

Ask anyone who’s raced karts over the past two decades and the chances are they’ve driven a kart powered by Honda’s four-stroke GX160 engine. The much-loved GX160 is here to stay but is it time it was brought up to date? Could the larger capacity GX200 extreme engine with a more consistent power output and less than half the price of a top SP 160 engine be the future of four-stroke racing? We get the inside line from Pro-Kart tuners, RPM Motorsport.


Pro Kart sprint championship racing began in the early 90’s and at one time was the largest kart grid at many kart circuits, I can remember racing in the RatPro run Honda challenge at Wombwell with 120 karts and a separate final grid of just novices

Over the years chassis, tyres and rules have changed but the engines have remained the same base unit, out the box, remove the restrictor, change the valve springs and race, in theory. Due to the inconsistencies of the GX160 engine people tried to change the engine to get the most out of it they could, not all these changes were in the interest of the sport and a set of engine technical regs were produced to try to keep the engines to a set level and have been used for many years with specially designed test equipment to try to ensure that all engines are as equal as possible. Various combinations of the Honda GX, World Formula and Subaru engines have been tried over the years but it always returns to the GX160 but with engine units now costing well over £1000 is it time for a rethink before we lose all the Honda Prokart  grids in the UK due to the high cost of competing at the top level.

Even Harry Webb likes a prokart hack…

Roger Pitchford Motors: RPM have come up with an idea that could turn Pro Karting on it’s head so we met with the RPM team at their workshop to find out the new concept.

KM – Ok Roger I have known you since 1994 when you could still fit in a kart seat and had hair, so before we get onto the new engines answer the question that most people ask, why do the 160SP engines cost so much?

RP – Because the MSA engine regs are an engine builders bible we have to produce an engine within those tolerances, out of a delivery of possibly 20 engines, when tested on the dyno machine you could get anything from 0 to 10 engines that are reasonably good but not up to top race standards as the engines are mass produced all the parts are slightly different in tolerances and its our job to strip all the engines to find the best bits and make the best engines we possibly can using only these parts, you can imagine the amount of wasted engine parts and engines that cannot be resold because nobody wants a basic engine.

KM – So whats the difference between a standard engine and an GX160SP?

PW – There could be anything up to 1.5HP at 6000 rpm between the 2 engines

KM – I can see the wastage involved in getting a top race engine but do you think that you have contributed to the demise of the Pro Kart grids as a lot of drivers cannot afford these engines and stop racing as they can no longer be competitive?

RP – No holds barred then! Ok yes if you put it like that then yes there’s no doubt that we have been part of the problem, as drivers demand more it invariably costs more it’s been a vicious circle.

KM – So why bring out a new variation of the engine if grids are falling?


PW – In sheds and garages all over the UK drivers have pro kart chassis ready for racing but they either don’t have the cash for new SP engines allowing them to compete on a level playing field or can only race a few times a year and cannot justify buying them. The new engine will allow them to race competitively at a fraction of the cost.

KM – I see it’s a GX200 engine does this mean you want to get rid of the GX160 engine altogether?

RP – God no! This is just an alternative and the drivers will be the judge of it, they will decide, we don’t for one minute want to stop the GX160 engines, they are the recognised MSA championship engine for Senior, Junior and Cadet championships and always will be, we hope that it will be an alternative grid for owner driver sprint and endurance meetings.

KM – So how much is the engine going to be?

RP – £400+vat?

KM – That’s a great price, for how long and when will it go up to over £1000, don’t forget this is to be published and we will keep you to it – forever!

RP – Hate you Capenhurst! We will fix the price for 3 years depending on the retail cost from Honda of the base unit and will only increase in line with that.

Piers Prior driving for Team Karting Magazine

KM – OK that’s 3 years but then do we go up to the £1000 mark?

RP – I might regret this but after 3 years any engine increase will be in line with inflation. Happy now?

KM – Nice one that’s what we wanted, and in writing as well! So how can you keep the price down to £400+vat per engine?

PW – Each engine is rated 7.2/7.3 HP on our dyno machine (could vary slightly on other dyno’s) and to get there we can make any adjustment to the engine we want to which allows us to balance them and standardise them throughout the rev range, because we can do this to every engine we buy there are no wasted parts or motors making it all cost effective.

KM – That’s fine but how do you keep them all level and stop drivers making their own adjustments?

PW – All engines will have a seal on the crankcase, head and carb and nothing will be able to be changed, it is to be an economy engine and this is the best we to do it.

KM – How do you intend to control the engines if they are used at many different circuits?

RP – Obviously if a driver buys engines they can use them anywhere they want to but if they do a race meeting at any circuit for example, PFI or Stretton in an owner driver meeting or championship then there are certain rules associated with the engine. Each circuit will be supplied with spare engines (depending on grid size) the race organiser can change any engines for a new one at any time if he feel that there is a problem, at the end of the meeting the winner or any other driver can have his engines changed by the organiser or scrutineer, it’s up to the discretion of the circuits involved. There is also a buy back available at standard engine price and this can be arranged with each circuit. We also reserve the right to check any engine at any time to ensure it is within the stated engine limits, this could happen at any race meeting with our mobile dyno unit.

Chris Mccarthy ready to race in a GX200

KM – Will there be any guidelines for circuits?

RP – Yes we are just working on a guideline sheet for any circuit that wants to run the engines within their club meetings

KM – What about service charges?

PW – these will be the same as the 160 engines as all service parts are the same but we are working on a possible service exchange system which will possibly work out cheaper.

KM – So who’s running the engines at the moment?

RP – we are running at PFI on their Sunday owner driver meeting and also we have a grid at EPEC in all the rounds for the pro teams and all the top teams are now running the engines. If we are at the sprint meetings like PFI drivers can hire engines from us for £50 per engine per day if you arrange it with us before the meeting, we have a lot of interest from circuits who have not had a pro kart grid for years and drivers who had given up sprint racing due to high engine costs are returning so it is working we are getting drivers back onto the grid.

KM – Does this mean that the GX160SP engines are going to be worthless after drivers have spent a lot of money on them?

RP – Not at all the 160’s will still be run within the MSA and at non MSA meetings alongside the GX200 extreme and if drivers want to change to the faster, cheaper engine then they can always sell them to the cadet drivers who always want top engines.

ProKart racing is close, frantic and value for money

At a recent meeting at PFI Roger and team supplied the engines on a pool basis drawing the engines by number, most drivers had them fitted within 30-45 minutes and ran them throughout the day with no problems handing them back when finished. The lap times at PFI were 1.5/2 seconds a lap quicker, with more engine performance throughout the range. Speaking to all the drivers there were no negative comments from anyone, only encouragement and support.

So love him or hate him Roger has taken a big move forward in the pro kart class and a massive investment to try to revive the entry level class of karting, its true that we were losing drivers every year and something drastic had to be done, this could give the class the boost it desperately needs with a long term structure put into place with set costs, contact RPM for more information.

T. 01543 473548 /


Like this article? Then read more Tech Tuesday here:

Tech Tuesday – Rotax Max Evo: 10 things you need to know

Tech Tuesday – Engine cleaning