The Rhino clutch cover explained
The Rhino clutch cover with its increased capacity makes a very big difference in engine longevity. It’s basic mathematics that when oil takes an x-amount of time before it’s so contaminated that it needs to be replaced, that increasing the amount of oil by 25% will increase its lifespan by the same 25%. I challenge everyone who claims that it doesn’t make any difference how much oil is in the engine, to put their money where their mouth is and reduce the oil level by 50% or so in their engine and ride it that way… I also challenge anyone who thinks that 1.2 litres is enough for a 510cc EXC for road use to explain why KTM says the 690 needs 1.7 litres…
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But there is more to the Rhino cover than that. You have to understand the fundamentals of a combustion engine to see its potential. If you increase the oil level in an engine, any engine, then you’ll decrease the air volume above the oil. As the piston goes down the pressure inside the engine increases, putting pressure on seals and gaskets. That’s why simply raising the engine oil level may result in blown gaskets and seals. The pressure created is roughly the difference between piston up and down, plus a small amount of pressure created by the whirring gears and the combustion gasses past the piston rings known as piston blow-by. As the Rhino cover increases the oil capacity but even more so the volume of air above the oil, you can raise the oil level and still have more air above the oil compared to OEM. In effect you’ll have more oil and yet less crankcase pressure.
How much more oil depends on your bike, on average it’s 300cc bringing the total to 1.5 litres but we also have a 2018 EXC 450 which now fills up to 1.7 litres. What we do is raise the oil level to the top mark in the OEM oil level screen, which still gives you more air above the oil level than OEM. Now 300cc may not seem like much but on an engine which normally holds just 1.2 litres it’s an increase of 25%! On an EXC used for travelling (ie not racing it flat out) you can change the oil after about 2000km. Adding 25% oil immediately brings that up to 2500km. The oil increase is only part of the story though. With its greater frontal capacity it also keeps the oil cooler, which especially in an engine with a small oil capacity like the EXC is vital for longevity of that oil. |
A 10/60 oil is basically a 10 oil with additives to make it behave like a 60 oil when hot. If the oil gets hot those additives burn off, leaving you basically with a poor quality 10 oil. That poor quality 10 oil has lost its viscosity and will more easily burn off past the piston rings, gumming the rings up in the process with carbon deposits. You’ve now basically set a vicious cycle in motion. Sure, changing the oil will restore the engine oil viscosity but it will not restore the gummed up rings, which will make it easier for the combustion pressure to find its way past the piston and thus beak down the new oil even quicker. Preventing the oil getting too hot is of vital importance.
The combustion heats up the oil and the only thing the oil has to dissipate that heat is the engine casing. The OEM clutch cover is almost streamlined, resulting in negligible cooling, the Rhino cover has a much bigger frontal area. |
The Rhino cover is also much stronger that OEM. A thrown up rock can find its way through it, which is why some fit protective covers. It protects the clutch cover, but does it in the same way a plastic cover would protect the radiator… stones will no longer damage it but it won’t cool anymore either. In effect you’ll sacrifice the engine for the radiator. The Rhino cover doesn’t need protection and thus keeps the engine oil cool too.
Finally we have machined a pocket in it just under the clutch. An idea which came from my time working on industrial machines. As the clutch wears, the friction material coming from the clutch plates is pushed to the outside of the clutch due to centrifugal force. With the OEM cover that material will find its way into the engine oil and travels through the whole engine. It’s broken up by the gearbox gears and mulched into a fine pulp, a very abrasive pulp which is fine enough to find its way into the oil pump and from there-on through every oil channel and bearing. The Rhino cover, due to its shape, catches most of it as it has a parallel ‘wall’ around the clutch basket. At the bottom is a small catch tank which will collect the particles sliding down from the wall as they are heavier than oil. That catch tank has its own drain plug to remove the material. How does it work in practise: We do test our products extensively. Both our EXCs are fitted with the Rhino covers and have covered well in excess of 30000 km each, loaded up with camping gear and without either of them needing any engine work. They still feel and sound like a new one. No rattles, no extra engine noise and no noticeable oil consumption. Even on the hottest days we’ve never had to add oil in either of them which is a good sign the rings and piston are fine. |
We use our EXCs for off-road travelling but also for 1200km days on the German Autobahn on our way to Sweden and Norway in the middle of summer. Summers are not Australian hot here but being stuck in the annual traffic jams around Hamburg, which can take hours to get through, makes them hot enough to burn your legs. I think it’s fair to say our EXCs get their fair amount of hard use. In those conditions we found that changing the oil after 3000km is perfectly fine. The oil that comes out after 3k is not black, not burned and still viscous. To err on the safe side though we stick to 2500km (it also makes it easier for my brain to remember when an oil change is due eg 5000, 7500, 10000, 12500 etc). But we’ve also done a 4000km stint when oil was hard to come by, and it was still fine.
You may think we feel KTM has made an inferior product with the EXC? Absolutely not. The contrary in fact. KTM made an enduro, not a travel bike. An enduro isn’t designed to get stuck in traffic for extended periods of time, or to be used on the autobahn for 1200 kms straight, or slowly climbing up a steep mountain path while loaded up with luggage. An enduro is designed to be raced for short periods of time. Racing puts more strain on the engine but it also gets more cooling. It was designed for a different purpose, however it’s that well build that with a few modifications you can use it as a travel bike.
Should KTM have increased the engine oil capacity? Well, no. KTM specifies the engine oil to be changed after 15 hrs or after every race. They don’t need the oil to last any longer. They also don’t need the extra cooling area as the oil only needs to last one race. Clutch debris spreading its way through the engine isn’t that much of a problem either when you rebuild it after 70-130 hrs anyway.
For us who want to use it for traveling over longer distances, changing the oil every 15 hrs and doing a rebuild after 70-135 hrs is a bit problematic though, as is oil burning past the rings. Keeping the oil cool and in good condition is vital. But if you’re willing to do that then you might not changing anything, although you’d still be more vulnerable to rocks.
What we made is modifications to make travelling on an EXC easier. In the same sense as adding a luggage rack will allow you to take luggage more easily, and a larger fuel tank will give you more range. Or fitting a steering damper will make riding in sand a lot easier and cush-hubs will give you longer chain life and give you more comfort.
You may think we feel KTM has made an inferior product with the EXC? Absolutely not. The contrary in fact. KTM made an enduro, not a travel bike. An enduro isn’t designed to get stuck in traffic for extended periods of time, or to be used on the autobahn for 1200 kms straight, or slowly climbing up a steep mountain path while loaded up with luggage. An enduro is designed to be raced for short periods of time. Racing puts more strain on the engine but it also gets more cooling. It was designed for a different purpose, however it’s that well build that with a few modifications you can use it as a travel bike.
Should KTM have increased the engine oil capacity? Well, no. KTM specifies the engine oil to be changed after 15 hrs or after every race. They don’t need the oil to last any longer. They also don’t need the extra cooling area as the oil only needs to last one race. Clutch debris spreading its way through the engine isn’t that much of a problem either when you rebuild it after 70-130 hrs anyway.
For us who want to use it for traveling over longer distances, changing the oil every 15 hrs and doing a rebuild after 70-135 hrs is a bit problematic though, as is oil burning past the rings. Keeping the oil cool and in good condition is vital. But if you’re willing to do that then you might not changing anything, although you’d still be more vulnerable to rocks.
What we made is modifications to make travelling on an EXC easier. In the same sense as adding a luggage rack will allow you to take luggage more easily, and a larger fuel tank will give you more range. Or fitting a steering damper will make riding in sand a lot easier and cush-hubs will give you longer chain life and give you more comfort.