The bare junior engine is exactly the same as the bare minmax engine. The difference is the minimax has both a carburettor restrictor and an exhaust restrictor, along with different ecu (minmax and senior run the same ECU) The only difference between a Junior Rotax and a Senior Rotax is that the senior has a power valve. This means that the cylinder head is slightly different to accommodate it.
Junior Rotax is quick – VERY quick. Coming into this class with no previous owner-driver experience can be daunting. Juniors are often faster than seniors at some tracks and it's probably the most hormonal-fueled competitive class out there. That said it's also such an exciting class and there can be some of the best racing you’ll see anywhere. If you’re only previous experience is indoor rental and your teenager wants to go outdoors then there are a few things you really need to understand. Even the fastest (DMAX aside) rentals are slower than cadet karts, much heavier and will use a long durable tyre. To note DMAX karts are
similar to junior Rotax in that they use the same bare engine, but are configured for durability and reliability as opposed to speed. The chassis are much heavier and stronger and the tyres are much longer lasting.
You can get away with a bit of contact in rental karts, but making contact in a junior will most likely lead to an accident where the kart will need significant repairs – or worse repairs to your driver too!
So take it STEADY! – but not too slowly as that causes problems too… but more on that later!
Engines – Evo / Non Evo
You’re probably looking on Marketplace or Ebay looking for junior rotax and you’ll see the term Evo / Non-evo - So what’s the difference between n Evo & non-evo? That’s not a simple answer…
It’s really important to understand the differences and the terminology used. The rule of thumb is if it’s listed as an Evo then it usually is. However, non-Evo can cover a lot.
Let’s start with the pure engine part.
The main difference between an Evo and non-Evo as follows and I’ll cover the power valve too even though it's not relevant to junior Rotax. Firstly visually, to look at the evo has a red top and black crankcase. The non-evo is not painted so has just a bare metal look.
The next thing you’d see is the clutch – the non-evo has holes in the drum which are easily visible.
The EVO has a different clutch block and the drum is solid and stronger. The non-evo had a cast aluminium barrel, the Evo had a CNC barrel. This was the major change and while some barrels are better than others, they are ALL in the same ballpark, whereas in pre Evo
some barrels were significantly better than others. That doesn’t mean there weren’t some great non-Evo barrels but less likely. Plastic internal gears were used on the non-evo – these were upgraded to metal on the EVO.
The power valve was not electronically triggered, whereas in the evo it is now controlled by the ECU
and solenoid. So the difference between a non evo and Evo at an engine level is not insignificant BUT here’s the thing. Pretty much every “non evo” has had the clutch upgraded, plastic gears replaced and probably had an Evo barrel put in - which makes them essentially an “Evo”. But will still be advertised
something like - non evo with Evo internals. These engines are certainly comparable to EVO engines.
Now for the but….
This is only half the equation.
When they released the EVO they also upgraded all the ancillaries.
These are :
Exhaust - better flow, and 2 parts not a single piece.
Loom - more reliable.
Upgraded coil pack.
Battery box - which now holds an Ecu.
Added an ECU which controls timing etc and the power valve.
The power valve uses a vacuum but is controlled with an electric solenoid linked to Ecu/timing etc.
carburettor - way less temperamental and more powerful.
Air box - looks better.
The ancillaries are so much more important than you think. They make a massive difference to running and reliability overall.
So a kart listed as non-evo could be an old Evo with old engine bits and old ancillaries or it could essentially be just as good as an EVO. It’s really important to understand this as seeing 2 karts at similar prices or one a bit cheaper may not be the better option. The ancillaries alone are around £750 - £900 – so buying a kart that’s £400 is more expensive but having these will really be worth it.
So what you’re saying is I can still just get going with a non-evo though right – I mean my child won't need the extra performance to get going and we can upgrade later right?
Sure! – BUT…. As well as there being a power advantage, the biggest advantage with the EVO
ancillaries is the reliability. The jetting range is narrower, meaning you’re less likely to get it wrong.
The electrics are so much more robust, meaning you’re unlikely to be standing there scratching your
head with “intermittent” running issues. Don’t get me wrong in the hands of someone who knows them – they can be very competitive and run all day long – but if this is your first Rotax, having something that starts the first time and actually getting you out on track is not to be underestimated.
Chassis
There are several different manufacturers. The main ones are OTK, Mad Crock, Compkart and Kart Republic and recently X-Kart. OTK covers the following, so if you see any listed as this, they are ALL the same chassis – just different colour schemes. However, there are differences in year of manufacture. For example, the following could be listed but are all essentially the same: Alonso, RedSpeed, OTK, Tony Kart, EOS, LN (Lando Norris). Gillard used to be their own chassis but recently OTK took then over so now, Gillard chassis from (I think 2022) are now an OTK chassis. What this means is that you can interchange components as they are all the same. OTK is the most
popular and there is a huge array of spares out there and OEM offerings too, which make a great choice for beginners. It also means if you need a space someone is likely to have one at track. While they are the same as mentioned there is a difference in years. For example, a 2016 Tony Kart is identical to a 2016 Alonso, however a 2017 Tony Kart is DIFFERENT to a 2016 Tony Kart (Upgraded brake calliper for example). It’s important to do your research on this if you see one for sale.
Which chassis is best?
What’s better a Ferrari or Lamborghini? Some chassis are going to suit other drivers better. However, an OTK is still one of the easiest and still performs at the very highest levels, with a great spare available making them cheap and easy to locate.
Day one at home with your new baby.
Power Republic Youtube channel – this is your new friend. Go through there as they have some great videos on changing all things on your kart. Well worth the time. The more maintenance you can do yourself the better.
Let's just run through a little scenario…..
You’ve ignored everything I’ve said so far and bought the cheapest non-evo you can find and you’re ready to go take on Lando Norris at your local track!
The first thing you’ll do is get some fuel – let's hear this baby roar!!! So I need some 2-stroke oil, where can I get some today? Halfords! Let’s measure some out – that looks about right. Ok, that’s petrol in. Let’s start her up!
It’s started!!!
That’s a lot of smoke – have I bought an old knacker? – I really shouldn’t have done this in a closed garage!
I’ll open the garage door, and get some air and leave it ticking over while it warms up. Oh… Janice! Billy! – look – the karts running!!.... yeah, great, isn’t it? Yeah… oh… it’s cut out. Restart it…. oh, its not starting? – Try again…. Nope… let’s change the plug…. This will do out of the family Fiesta… It’s started… ticking over…. Oh its stopped again. Why won’t it start?? I’ve been conned! I’ve been sold a piece of “rubbish” …. I hate karting…. Stop crying Billy….STOP!
Follow these tips before you even try to start.
Get the right oil!
These are high-performance racing machines. They are not designed to do 12,000 miles between services. They are not designed for nipping down the shops. They are made to get on a track and go at 100% all the time. As such you need the right oil. People will have different opinions but I would recommend Silkolene Pro-KR2. This is a semi-synthetic oil as opposed to a full castor-based oil. It’s specifically made for Rotax and is a homologated oil so you can use it to race with. It’s much kinder on plugs than other oils and will be one less thing to worry about when you start. I cannot stress this enough DO NOT USE NORMAL 2 STROKE OIL from your local garage or halfords. It will bung up your plug quicker than anything and you kart will stop running and fail to start.
Get the right plug
Denso is the plug of choice for Rotax. These range from an IW24 – IW34 – depending on the ambient
temperature, but to start don’t worry about this, an IW27 will be the plug you use the most and will be perfectly good.
Starting for the first time.
The first thing to remember is if the kart has been sitting there will be no fuel in the carb. If you look
at your fuel tank there is is a smaller catch tank, with a lid with a hole in it. This is so the pressure in the tank is kept neutral. Don’t block it up! Or it wont start or cut out after a short while. Put a tube in the top and blow in and you’ll pressurise the tank slightly causing fuel to run to the carb. Do this a few times until there are no bubbles coming back from the carb. Put the choke and start. As soon as it starts and you are able to rev it– take off the choke. You will only need the choke for starting first thing in the day or after draining the carb and re-priming just to help pull through the last bit. You should never need it between sessions. Ok, it’s running – this is a good time to use one hand on the revs and swap to the brake to check they work correctly. It should be easy to lock them up. Keep the revs up. To be honest, unless you have a reason to run it on the stand, rev it a few times and then cut it off.
DO NOT LET IT TICK OVER – EVER!
They are not designed to tick over – most don’t and that’s completely normal. They need to be revved to combust properly, so if they are not being revved it just chokes up the plug. If you don’t have a reason to start it – don’t.
This goes for on the grid, start it in your pit bay, and give it a good rev to make sure the plug is cleaned
out (by revving – don’t try to clean with wire wool – you’ll just remove the iridium and make it worse) then switch it straight off. Don’t start it again until you’re ready to move away from the grid. Smoke – they do tend to smoke a lot when cold. Ensure you have the right Petrol / Oil Mix : 120ML / 5 Litre of fuel.
The smoke will clear as you go faster and it warms up.
Before your first day
There's so much to potentially check – but stick with the basics. Hopefully, all your alignment is ok and its something you can learn to check yourself as you get more confident with the kart.
Brake cleaner –
You will use a lot of this. It’s worth investing in a pressurised refillable container as it’s far cheaper than buying cans. It’s great for cleaning especially things like carbs etc. Carb cleaner is good – but BEWARE is a solvent so can affect some components. Only use on metal where there is no contact with rubberised parts, paint etc. It’s worth taking the carb off. Take the bottom off – be careful as the floats will fall out. Check they are “floats” and don’t have any petrol inside them – this will cause terrible running issues.
Give it a good blast in all the jets with brake cleaner. Then use an air hose to blow through. While you’re at it, there is a 12mm nut on the side. Remove that and you’ll find a little filter. Be gentle with it and just clean it with brake cleaner and gently blow it dry. Remember to try and align the filter so the mesh is upwards when the bolt it fully tightened. While this isn’t a full rebuild it will help prevent 90% of your issues. If you feel confident – follow the power republic YouTube videos and give it a rebuild. While you’re at it – rebuild the fuel pump too – it’s an easy job and again, just helps stop those stupid first-day problems on a kart that’s an unknown.
Battery
Most newcomers don’t realise there is no charging system on the kart. All power comes from the battery and is the number 1 cause of bad running. Often, I see new people who are having starting issues (because of using the wrong oil, dirty carb or pump) and when they finally get it sorted, they don’t realise the battery is virtually dead – and yup… it starts running badly and causing more issues. Ensure the battery is fully charged before going to track -and if possible, take a means to charge it up while there and keep it topped up all day. Or take a full charge spare. Again – ensure you use the correct battery. Yusa YT7-BS is the accepted standard.
Gearing
So this is often overlooked for a first trip out – you just want to get out! - and I may be slow but it won’t cause an issue right??? – wrong. Find out what people are using and add at least 2 -3 teeth if you are starting out. For example, they may say 12/74. The 12 refers to the front sprocket and 74 for the rear. Add teeth and you have better acceleration; remove teeth you have a better top end. To start with you need the revs. In this
scenario start with a 12/77 at least. If you go to a track where the fast kids are running 12/76 and you rock up with a 12/72 on, not only are you going to be very slow you simply won’t be revving the kart enough. And what happens when we don’t rev the kart? The plug bungs up and it stops running. This can happen really quickly – you’ll see top drivers pinching their fuel lines on the formation lap to try and lean out the kart to stop this from happening – and that’s just one slow lap with a fast driver in the kart.
Get the right gearing.
Remember to check the chain tension – you are looking at about 10-15mm of chain movement.
First Day On Track
Well, this is going to be… a nightmare! – IF you haven’t taken any of my advice if you have, you’re still likely to have issues you don’t expect but you can mitigate most of these.
Tyre Pressures
Different tyres / different days / different tracks – all make a difference to tyre pressures. So it’s hard to advise on this – the best advice I can say is to try to find out before you go – or ask someone when you’re there. Tell them it’s your first day – most people will give you a good starting point. If you really don’t have any help – put in 12 all round and go from there.
The first thing to remember, you are not going to turn up and beat the local kids – don’t even try to.
First Session
Your first goal is to make it around a lap. I’m not joking – depending on what tyres you have they will be like blocks of ice for at least the first 2 laps. And that’s with a seasoned driver at the helm. You’ll be in the catch 22 of not being able to go fast enough because your tyres are cold, but needing to go faster to warm them up.
Just take it steady – the tyres will come on eventually but those first corners are horrid. Start at the back of the grid. Build your speed up – try to give it as much as you can on the straights otherwise, your plug is going to bung up pretty quick. Once they do – they go in the bin. It's ok to brake early and get around the
corner safely, but do try to give it some down the straights.
Don’t worry about anyone else on track. HOLD YOUR LINE! – An experienced driver will overtake YOU – don’t’ try and get out of the way or fight another driver into the corner just hold your line and lift off slightly and they will be past you. If you move, you’re likely to cause an accident as they will have already committed to coming down the inside or outside of you.
With that in mind if you can find a track open all week – a mid-week session when its’ quiet is a REALLY good idea! That’s it you’ve survived the first session! Go home and sleep! – It’s harder than it looks!
Remember to refuel and use chain lube between every session and repeat!
Hopefully, by this stage, you’ve found a few allies in the paddock and can continue your journey!
Good luck!
