Tech Tips #2
By Evan Lyons
G'day guys and welcome to our second tech tips article for this year. As time goes by I will add or pen tech articles aimed more or less at the lesser experienced or newer guys to superkarting.
Some of the more experienced guys may do well to have a read as well!!
Here's another scenario for you more (or less) experienced guys to consider.
How often does someone bring a kart to a meeting covered in grime and shit, they get the thing up onto a work stand and then they proceed to try and rebuild the bloody thing half an hour before scrutineering closes and practice begins?
Quite often actually!
Many years ago I used to race sprintkarts and I was getting my pit area set up for a big meeting at Oran Park near Sydney N.S.W. The meeting was the Castrol International and was regarded as a reasonably big international event at the time. I was just about to present my kart to scrutineering when these dudes drag out an absolutely filthy, greasy, shitty looking kart out of one of those really trick, mag wheeled, electric braked, multi-level kart trailers with all the you-beaut lockable tool compartments and flashy sponsors and kart/engine makers graphics and logos down the side, filled with a million kart bits, racks of spare tyres and numerous, mysterious looking jerry cans skulking in the corner. You know, the "Money Is No Object And I Don't Mind Telling You About It" type? Anyway, these dudes drag out all this gear and set up their pit and next thing you know is they are asking all and sundry about them if they can borrow extension leads 'cause they want to do a cylinder hone and install a new piston and are too far away from a power point!! Yeah, sure, and pigs fly too! Bugger me if the guy doesn't fish out of one of his trailer's lockable toolboxes a big electric drill and a bloody expensive looking parallel hone and starts waving it around! Next thing is they lift the barrel off the engine, clamp it up in a vice and start honing away! His mate proceeds to strip the kart right down to its undies and between them they do pretty much a complete rebuild on the thing. Now I have been guilty of late kart prepping on Saturday night before races on Sunday but, please, doing a complete rebuild on a kart in the pits just before scrutineering and practice for a big two day international event is the the last word in lack of preparedness!!
Kart preparation can mean the difference between a complete hell day without finishing an event or a successful and enjoyable day out at the races. I'm not going to bother here with engine rebuilds and regular piston and ring replacements. There are too many variables here and so many jokers have their own ideas on how long a piston or ring should last. All I will advise here is to follow what the manufacturers recommend for road racing engines with regards to component inspection and eventual replacement.
It is very often the simplest of things that can ruin you race day, so I have compiled a list of things to do before you race, indeed before you even take to the track in your new toy! This is a useful preparation regime if you happen to buy a used superkart. Be very wary of preparation by other guys as they may not be particularly vigilant with their maintenance and may have just tarted up the kart to sell.
These parts can hide a variety of sins and only get in the way whilst you are cleaning and working on the guts of your machine. Often times seats left in place can hide a failing engine mount or gearshift linkage.
This is possibly the best form of preventative maintenance you can do to your kart. Just the act of running a rag over every inch of you kart can reveal potential dramas before they actually occur. Avoid the use of high pressure water blasters and such as they have a habit of forcing water under high pressure into wiring looms, gearbox and carby vents and even past gaskets into the bowels of the engine! This can promote corrosion of critical parts, particularly if the kart is left for long periods of time between meetings.
Use a bit of kerosene on a rag to remove that stubborn splattered chain lube. Loose and missing fasteners, fuel, oil & water leaks, chaffed wiring looms, fuel lines, brake lines and cooling system hoses, cracked engine mounts and chassis and a myriad of other gremlins can be found under all that grimy, abrasive black shit. If you clean every inch of your kart you will become quite familiar with all those inches and will soon see any potential dramas before they become a real drama. A bonus of using kero is that it will buff up quite nicely and doesn't seem to affect paintwork or powder coatings like other solvents. Work out for your self a logical order of cleaning and inspecting the kart, such as starting at the front right corner and working your way around the kart or across the kart or whatever system you feel comfortable using. Stick to it! If you use a simple order such as this every time, you are guaranteed to get to every bit and will learn to recognize early signs of dramas before they get a chanced to ruin your day later on. I usually take about only about 15 to 20 min to completely clean my 250 international superkart. Another bonus of cleaning you kart is that it looks really nice when tyre kickers wander past to scope out your toy. Show a bit of pride here!
I'm presuming that you have air filters fitted here. Follow the manufacturers recommendations here. Don't forget to oil up your foam filters with the correct oil for that filter type. Some foam varieties can be buggered up by using incorrect filter oils.
I personally use "o-ring" chains on my 250 twin. This makes the task of chain maintenance rather easy. Just a quick squirt of a proprietry brand of chain lube and check the tension and look carefully at the condition of the link clip. Now is probably the time to change any sprockets if you are running on a different track next time. Have a good look at the condition and orientation (direction the open end of the clip faces) of the chain joining link and clip. These little items are responsible for many a chain failure. Superkart wheels are very small in circumference compared to motorcycles, therefore at the speeds that superkarts can go the chain is asked to wizz around fairly quickly and make two very abrupt direction changes around both sprockets. A poorly fitted link clip can fly off at a million miles an hour and "choonk" you have a chain laying on (a) the floor tray (b) the track or (c) bunched up against the crank cases and allowing your expensive gearbox internals to see the light of day! Not pretty. Clips are cheap so don't use them to death, replace them regularly. Ensure that the OPEN end of the clip faces AWAY from the direction of travel of the chain. Another item often overlooked is that the clips are stamped out of sheet metal and have smooth rounded edges on one side and sharp square edges on the other side. These sharp square edges must face outward or away from the chain. This is to help prevent the clip from slipping easily outward over the link pin grooves. The same is true of circlips used elsewhere. These circlips are manufactured by the same stamping process and the difference between the stamped, curved edges and the sharp edges on the other side are quite marked. Always orient these clips so that load direction on the clips is bearing on the sharp and square side, NOT the smoother rounded off side. This is rather important and usually overlooked. The exception to this rule is where circlips are ground or machined square on both sides to enable load bearing in either direction. Often found in transmissions. Another trick is to orient the joining link so in the unlikely event of a link coming apart, the link works its way out and AWAY from the engine. This can prevent the link from chewing the crankcases on its way out.
Chain tension is not super critical on a superkart, but given the circumference of the sprockets and the distance between the gearbox output shaft and axle centres, can be rather fiddly to get just right. Remember, keep chain slack to a minimum here. Be careful not to tighten the chain up guitar string tight as it places excessive load onto the output shaft bearing and can lead to possible bearing or chain failure. Just a couple of millimeters of free chain slack here! If the chain twangs like a bass guitar string perhaps you should consider loosening it a bit. Turn the axle over by hand to determine if there are any tight spots and adjust accordingly.
Chain adjustments usually require loosening and retightening of several engine mount bolts (unless you have a remote chain adjuster fitted) so now is a good time to check tighten all those fasteners that you may have loosened to do the chain and others such as axle bearing hanger bolts, brake caliper bolts, steering components, pedals, gearshifts and other sundry fasteners that may cause lots of irritation, damage and pain should they undo! Now is the time to replace all those spring washers and "Loctited" second lock nuts with Nylok nuts. These little blighters use a nylon insert to provide friction and preventing the nut from coming right off the threads. Note: Nyloks will not prevent eventual loosening of fasteners, just prevent them from dropping right off the threads, so give them due attention in the critical areas mentioned. Don't ever trust them!
Cables such as throttle cables, gearshift cables (if fitted), exhaust valve actuator cables and the like should be regularly checked for correct tension, free running, and overall outward condition. Pay attention to reusable joiners used on throttle cables for loosening. If the cables run roughly they will need to be lubed with (preferably) a light machine oil. I use something like WD40 or RP7 for this. Pay attention to the adjustment of throttle cables. Ensure that the pedal hits its travel stop at the same time that the carby/s go wide open throttle. During the heat of battle out on the track you will be stamping pretty hard on the loud pedal and if you are having a drag race down the straight it is amazing how jamming the pedal down even harder onto its end stop , possibly even bending it, makes you feel like you have a better chance of passing your adversary! If the carby is wide open and the pedal has not reached its travel stop the usual result is a broken throttle cable, or at the very least a very stressed cable inner and bent throttle pedal! This can really piss you off if you were dicing for the lead in a state championship final and a cable breaks! A little attention here can multiply the life of throttle cables immensely.
A little thought to the original installation can make the world of difference in the long run here. Wiring on basic karts can be very simple but on fancy 250cc twins with digital ignition and exhaust power valve actuators, data logging facilities, Digital LCD dashes, electric fuel pumps, battery charging systems etc. the wiring looms become bulky and very messy unless a bit of forethought is put into the installation. Often wiring looms are lifted straight off the motorcycle that the engine came from. Now this is fine if the kart installation mirrors the bike, however, this is rarely if ever the case. These harnesses need to be stripped of wrapping tape and all the wiring laid out onto the kart in neat bundles and re taped. Often this means that some wiring is too long and others too short. The temptation here is to leave the longer wires just dangling around and the shorter wires stretched too tight on their terminals. This type of setup invites fatigue and eventual breakage in the wires and terminals and possible shorting due to chaffing on some sharp bracket, usually resulting in an eventual failure. These failures always seem to occur after practice and about 1.5 laps into the first race of the day! Spend the extra effort and shorten lengthy wires and lengthen too short wires. If possible, use colour coded wires the same as what is used in the original loom. Solder these connections and support the join with heat-shrink tubing. Use heat-shrink tube to support wires where they come out of earth lugs and switches as well. Ensure that all the wires are the same length especially where the enter connector plugs and so forth. This will ensure that all the wires share the load if they are pulled about and help prevent wire breakages. After making up you harnesses to length to suit your kart installation, re-tape the whole loom with electrical tape. Don't make the mistake of using re-usable "scotch-loks" or wire connectors that require crimping or the use of a grub screw to join. These type of thing may be fine for bodging up a shitty old FM radio under the dash of your old Datto 1600, but are useless in the long term in the component abusive, high vibration, extreme weather environment of a racing superkart. They have a nasty habit of crushing the wire and creating stress points and are notorious for corroding around the wire strands and creating the worst type of electrical fault of all, the dreaded intermittent fault! Cleanly broken wires are relatively easy to trace and repair but an intermittent fault can ensure a frustratigly shithouse days racing and hours of tedious fiddling to trace the fault. These faults will almost never show their ugly little zit heads in the workshop or at private practice! Usually they rear their mugs early in race one and then every race thereafter! The addition of nylon "spiral wrap" or flexible plastic tubing designed for tidying up under bonnet wiring in cars is a worthwhile step and protects the whole harness against chaffing on sharp metal parts. Motorcycles are usually fitted with fairly good quality weatherproof connector blocks but if you need to replace these, replace them with good quality weatherproof connector plugs. These can be sourced through auto electricians or auto accessory shops. It is very important to use correct soldering techniques to avoid the dreaded "dry joint". These joints are about as useful as twisting the strands together and using chewing gum and a rubber band to hold it together! If you doubt you own ability to solder correctly, you should be able to find someone in your club with soldering experience to help. If not, it would be a worthwhile investment to visit an auto electrician. These guys do this type of thing for a living and although this may cost some, at least the job should be done right. As a bonus, if one of his solder joints fails due to a dry joint you can pay him a little visit and shove the loom firmly up his bum! Seriously though, these guys have a reputation to protect and bad soldering is not a very good advertisement for their trade. Wiring looms, cables and fuel and coolant hoses need to be run in smooth, straight as possible runs and secured by "P" clips, electrical tape, cable ties or all of the above. Coolant lines are rather heavy and are notorious for chaffing where they run over chassis rails and such. If the karts are seldom cleaned oil and dust mix to create a wonderful grinding paste that just loves to chew up the soft rubber of coolant hoses. Then one day when you least expect it, hot summers day, drafting up the arse of the kart in front for most of the race, engine temp getting right up there....PHHFFFSSSSSSST goes the coolant hose! But did you hear it go? Nope! Coolant pisses out behind you and all over you mates visor behind you and a few laps later your engines exhaust note goes kind of funny and it loses a fair bit of power and you lift your foot off the loud pedal and are rewarded with a sudden deceleration even though you didn't touch the brakes! The deceleration increases to the point of locking the back wheels and of into the scenery you go. "Bugger it" you think, "Just flat spotted my new rear tyres"! The flat spotted tyres are now the least of your woes as the piston has gotten to really like the chrome plating it was in close company to inside the cylinder and has gotten very married to it! Endo one expensive barrel and piston assembly. The excess heat has also cracked the cylinder head as well and as a final insult, as you hoist your self out of the dead kart which is, according to Murphy's law, usually as far away from the pits as could be possible, you use the engines head as a hand hold as usual and cleanly burn the head stud pattern into the palm of you hand! Jeez you wished you'd seen the chaffed hose but because you didn't clean the kart thoroughly this time you didn't check things out as usual. Keep all hoses and lines loomed up and secured and if the have to run against chassis rails consider using a "P" clamp or using the next size up hose and sleeve the coolant hose and securing with a sturdy cable tie. No pretty but very effective.
Brakes require very special attention and, curiously, are often one of the most neglected systems of a kart. Time and again, as a scrutineer, I ping a kart due to faulty brakes. This is truly absurd as brakes are possibly the most important safety system on a superkart. Usually, the brakes just don't have enough "pedal" Ie: the pedal moves too far before the brakes actually work (if they work at all). Some drivers can get quite snaky when pinged for bad brakes and make smartarse comments along the lines that "Oh I don't need brakes to go fast, they only make me go slower" and other such shit! Well if you have ever had someone spin right in front of you in the first corner after a massed start and you've got nowhere to go you may just appreciate brakes that actually work. I reckon blokes say that type of crap to somehow justify their lack of preparation. Go figure!
There are plenty of other things to look for other than fluid leaks and level. How about the condition of the brake pedal and linkage/s or cables to the master cylinder/s? It'd be a real bummer if your pedal, cable or linkage broke! Rules for cables and linkage construction are clear and specific in your technical specifications book. Check for worn/frayed cables and condition of clamps and possible cracks and loose fasteners in linkages, bias adjusters and such. Check for brake hose damage. The best brake lines to use are stainless steel braided/teflon hoses. These hoses are usually expensive to have made but are well worth the money in terms of longevity and reliability, no question here. If you must insist on using plain nylon pneumatic tubing as brake line then consider replacing the tubing with the brake fluid at least on a yearly basis. Common brake fluid is made up of alcohol and vegetable oil and is hydroscopic or can draw in water in solution and this can lead to corrosion in the master and slave cylinders with consequent seal leakage and ultimately failure. Pay close attention to where the nylon tubing exits from the master cylinder and brake calipers as this is an area that is subject to constant flexing and stressing, particularly front brake calipers, The lines do need to be long enough to flex easily during movement of the steering components and can flap about markedly during racing, This can lead to weakening and a possible failure. Also pay careful attention to where the lines run. If they run over chassis rails use some fuel line that slips over the brake line and secure with a cable tie. Secure all other brake line runs to the floor tray or along the chassis rails using P clips, electrical tape or cable ties.
Note: NEVER use olive type compression fittings on nylon brake lines as with these type of fittings the olive can cut into and severely weaken the tubing. There are male barb/flare type of fittings available for this application and only need to be tightened up hand.
Take a look at the calipers, pads and brake rotor assemblies for leaks, loose or missing fasteners and wear. Check the condition of the brake rotors and smooth running of the wheel bearings. Give the stub axles a good wrench up and down and check for excessive king pin bearing wear.
This segment of your preparation could easily be given a whole topic to itself if you wanted to include engine strips and rebuilds, tuning and so forth. What we are looking for here is what may fail or break in the course of usual running so I won't touch on the subject of engine building and tuning.
Have a good look around the engine for fluid leaks from gasket areas and hose connections. If you are running a fairly complicated GP bike twin cylinder engine it is important to carefully check that none of the exhaust valve linkages and associated components are loose or have dropped off. Have a look at the actuator, cables and mounting brackets for looseness and condition. Check for expansion chamber flanges for leaking. It won't be too hard to see as oily, black exhaust shit will be all over the engine cases around the exhaust to barrel mounting flange. Any leaks here equals a loss in horsepower, it may only be a bit but it really matters in the small inch classes. Surprisingly, Silastic or other silicone gasket compounds work well on this very hot and vibration prone area. Check mounting springs for tension. Over a long period of use the springs will slowly hacksaw their way through the retaining eyes on the chamber and on the mounting flange due to vibration so its probably worth a look here to see if it could be a problem especially on older 250cc singles. Take a good look at expansion chamber mounts as well. These blighters are the source of much exasperation as they tend to break under the constant onslaught of engine and chassis vibration.
Speaking of mountings and bracketry, many guys still insist on fabricating exhaust, ignition coil, fuel pump and nose-cone mounts out of aluminium due to ease of cutting and bending and lighter weight. Aluminium, by it nature, tends to work harden and fatigue under constant bending from vibration and becomes very brittle and eventually breaks. Light gauge steel is far stronger and way less susceptible to vibration induced fatigue. If you add up the weight of bracketry made out of steel versus aluminium, you are not saving a significant amount of weight, but are introducing unreliability, when alloy is used.
Take a close look at ignition coil mountings. Over the years I have seen some beautifully prepared and presented karts sidelined due to laughably inadequate ignition coil mounts. Some people still insist on mounting these things up off the reed valve flange or directly to the cylinder head! Just because the plug lead is a bit short!. Up here, the vibration movements of big singles and their chassis are amplified and the idiotic little mount plates eventually just give up! Wires are inevitably strung in a haphazard manner and wire fatigue and eventual breakage and a DNF is the result. Mount these items securely to the chassis or directly to the engine mount plates and simply extend the plug wires to reach the plug comfortably without any tension on the plug wire. this way, the wiring can be loomed up and clipped/taped/cable tied to the mountings or along fuel line and throttle cable runs without the danger of pulling the wires right out of the coil. If you are running a coil type that relies on its bracket/mounting to return earth, consider running an extra earth return wire to the engine. Presuming you have attended to the coil mounting issue, and in the unlikely event of a coil mounting/bracket failure, the coil may flail around a bit but hopefully stay sort of put via its wires. The earth connection will remain and the kart will be able to at least finish the race.
It may be a wise move, if your kart doesn't compete for a while to drain the carby bowls. Racing fuel/oil pre-mix, if left for very long periods of time, can evaporate leaving an oily, gelatinous goo. This can clag up the carby jets and such so draining out the old fuel may be a good move. The same goes for the whole fuel system if a long period of inactivity is experienced.
Check tighten all coolant hoses and ensure all drain plugs are tight and lockwired.
Now is the time to check/change gearbox, brake reservoirs and coolant system fluids. If all went well during your cleaning and inspection routine and no obvious leaks were found this should amount to a quick level check or change. If fluid levels are unusually low then further investigation is required to determine just where and why the fluid is going. Unusually high water consumption could mean a leaking head gasket or even a cracked head or barrel or possibly a buggered water pump seal. I have had a leaking water pump seal in an old Suzuki RM125 and the blasted water made its way into the gearbox necessitating draining the gearbox after every race meeting! Don't ignore mysterious losses of oils and fluids. Its worth a mention to keep an eye on levels of fluids in overflow bottles. If you top up you radiator every time you run you will notice a buildup of coolant in the overflow bottle in a non-sealed cooling system. This is due to expansion of the water due to heat and the excess water vents via the radiator cap to the overflow bottle. If the line from the radiator cap to the bottle does not reach the bottom of the bottle, as the system cools and the water contracts air will be drawn back into the radiator via the recuperating valve in the radiator cap. Over the course of a few runs the water level in the overflow bottle will rise. This is quite normal and should not be confused with a leaking cooling system. Usually the amount required to top up the radiator will be sitting in the overflow bottle. If you want to stop this happening, simply position the overflow hose right down into the bottle and cut the tube at an angle to prevent the tube from choking on the bottom of the bottle. this is called a recuperating cooling system and ensures that the radiator remains constantly full of coolant regardless of it temperature.
Ensure all fluid filler plugs and radiator caps are secure and lockwired.
Hopefully by now you have run a rag, eyes and spanners over every inch and system of your kart and made any necessary adjustments, repairs or replacements. The time has come to replace all the goodies you took off before you started. Once again check out all the wings, sidepods, seat and bodywork for cracks, buggered fasteners and other damage. Refit all these bits. Check the wheel mounting flanges, bead areas and tyres for any damage and have a close look at the wheel mounting studs, nuts and bead pegs for looseness, possible fatigue and thread damage. Speaking of wheel nuts, it is a wise move to use flanged deep series nylock nuts. They are known as Nylok Wizz nuts or flange nuts. These little beauties have a washer built in to them, have heaps of thread length and have a nylon insert to at least prevent the total loss of the nuts in event of going out onto the track with loose nuts. You may bugger a wheel and stud set but hopefully you won't lose a wheel at half a million kph down the straight! A little tricky to source but well worth the effort. Now is a good time to balance those wheels. Bolt them up and your kart should be as ready as it ever going to be for an enjoyable days racing.
This maintenance regime is by no means complete as you may wish to add spark plugs, carby cleanouts, fuel filters, tyre changes and dozens of other tasks to your pre-race preparation. What I have tried to list here is a minimum of maintenance designed to ensure all systems and construction/assembly of the kart is at least looked at.