RJC Fury R1 Design Build Drive Gallery Video Contact Me Misc
Last page update was 23 Mar 2020

Cooling System

Essential Reading:

The plumbing on the R1 engine is fairly complex with many outlets/inlets and it is important to get it right as the R1 engine has a water cooled oil cooler matrix and you really need to be sure that this is working correctly. Some people have tried to simplify or alter the R1 cooling system design, usually resulting in problems. Richard  plumbed it up as designed and his car has been running for over three years without any problems on road or track. There are some additional pipes on the 2003 fuel-injected engine, making it slightly more complex. These are to implement a water temperature driven automatic choke. For the long gaps between the radiator and the engine, I'm using aluminum pipes, since this is lighter and cheaper and they will also not sag.

R1 Expansion Tank

The R1 radiator has an expansion outlet at the top, on the right of the radiator. It is just under the cap, pointing forwards and connects to a tiny plastic expansion tank that sits on the side of the radiator. This tank is not pressurised at all and has a header tank lid that is made of rubber and is a stretch fit. Any air or coolant that makes it past the radiator cap is pushed up through the over flow hose, which runs down to the bottom of this header/catch tank. This interior hose ensures that as the system cools, it sucks water back up through the hose and back in past the pressure cap on the radiator. The radiator cap has a dual, 2-way valve system to allow this. The system is therefore effectively sealed from the air and there should be no air in the system. The radiator cap should open when pressure exceeds (13.8 - 18.1 psi / 95 - 125 kPa).

There are several issues to consider with this installation in a car though:

  1. The extra pipe runs have increased the volume of coolant in the system. This is not a huge problem as water expands by a relatively small amount when heated, so the existing header tank should be able to handle this slightly increased volume change.

  2. I'm going to basically plumb the car in the same way as the R1 bike but, even with the radiator mounted as high up as possible on the front of the car, it will still not be the highest point on the cooling system. This means that any air in the system would naturally settle in the thermostat housing and pipework above the engine, which is not good. It also makes filling the system and removing all the air quite difficult as it would be trapped at this new highest point (within the thermostat housing).

  3. Space is an issue under the bonnet of a Fury. In particular the radiator height has to be right. The engine location and mounting height is also important. If mounted too far to the left and in too high a position, the thermostat housing and pipework will interfere with the bonnet location.

Air Collection Tank

To avoid any potential airlocks in the system and to simplify filling the system, I am planning to add a very small air collection and removal tank, mounted on the bulkhead to create a new highest point. This will require a single connection via a T-piece into the 'thermostat assembly inlet pipe (right)', which is at the rear of the engine (in my car) and is currently the highest point in the cooling system. This also provides a filler cap at the highest point. To keep the system operating as planned, this needs to be a completely sealed tank without a safety release cap. Ideally it would be transparent or have a window, so I can check to see if there is any air in the system but this is not that important. This is NOT another expansion tank. It will be completely filled with coolant and is not designed to hold any air in normal usage.

I bought a Rizoma fluid tank  from M&P  for £30 (the one without a window). It is a very small tank to reduce weight and is only 40mm tall by 30mm in diameter. It also weighs only 40g including stainless-steel mounting bracket and it is very well made. I have no doubt that it can take take the pressures involved since it has a nice thick rubber seal. It also has a very convenient single 7mm beaded inlet. It was designed to hold brake fluid so the plastic insert within the rubber seal is removed. If you leave this in place, it will not be water tight.

To fit the tank another Yamaha 7mm T-piece is required (as used to connect the water pump breather pipe to the head and choke) to connect it to the thermostat breather pipe. The exact location of this needs to be thought through so that it will not hit the bonnet.


I'm using a radiator from an 2003 R1. I bought mine relatively cheaply on eBay, complete with fan and R1 header tank. It is alloy and about 400mm x 300mm. The complete fan, radiator and header tank weighs 2.62Kg. Richard  used this radiator/fan in his car and I am very confident that it is up to the job. The radiator was never intended to fit onto the front of this car, so it will be necessary to make up some mounts. The 2004 radiator has the same connections but it is curved (to better fit round the engine).

Richard  made a combined mount, blanking plate and nose cone mounts. The bonnet is also mounted on hinges at the front of the car so my solution will have to similar but sculpted to the bonnet shape, so as to direct air through the radiator. I also need to mount the radiator off centre, to allow a horn and a cold air duct to me mounted beside it, feeding the air box.

You can see the temperature sender on the radiator in the above picture. The 2003 radiator does not have this as the sensor is in the thermostat housing.

It is worth spending some time with a wooden tooth pick, straightening the fins on the R1 radiator. The easiest way to do this is to take off the fan and to hold it up to the sunlight. If you can see dark patches, then the fins are bent. They are very thin and weak, hence easy to straighten (and break!).

The radiator has three mounting points with rubber lined top-hat bushes (6mm bolt hole and 13mm deep). A couple were missing on my radiator but the bushes were bought separately from Orwell Motorcycles  (part no. 90387-07391) for a couple of quid. The radiator needs to be mounted at the right height to clear the bonnet. Not sure if this is common, but my radiator is slightly warped. My design to mount it can accommodate this though.

For the purposes of pipework the following imperial to metric conversions are used: 1/4" = 6.5mm, 3/8" = 9.5mm, 3/4" = 19mm, 1" = 25mm. I find the interchangeable use of units confusing, so I've stuck with metric units. As you can see from the diagrams below, the general flow is up through the engine block and into the thermostat assembly. It then feeds into the upper right side of the radiator, as does the hot flow from the oil cooler. Cooled water exits the left side of the radiator and is fed back into the bottom of the engine. The complex arrangement of pipes and radiator, ensures the correct and balanced flow rates.

This part of the cooling system is not described in the R1 service manual, so I'll try to describe it here. The automatic choke takes a feed [R] from the cylinder head [P] and then passes this back [Q] into the cooling system via a T-piece [O] into the oil cooler breather pipe circuit. The easiest way to connect this lot up was to use the existing rubber pipes. Note that this image shows [P] not actually connected in the right place yet but the head outlet is hidden from view.

One part of the cooling system I will leave alone is the water pump outlet pipe (6) and the connection pipe (5) to the oil cooler (4) and connection pipe (7) to the water jacket (8). In this diagram, all I will change is the oil cooler outlet hose (1), which now goes off to the radiator.

Digidash Temp Sensor

I need to insert the 1/8" NPTF Digidash temperature sensor into the cooling circuit. I bought this 25mm diameter adaptor with the right sensor thread (part number GLOHA25) for 15.75 + VAT from Demon Tweeks .
On all of the R1 engine installations I've seen, this is mounted in the radiator inlet pipe. Daz  pointed out to me that this does not seem right, as this is the wrong side of the thermostat. The R1 water temperature sensor is mounted in the thermostat housing and sits on the head side of the thermostat, which supports this view. So, I'm mounting my DD2 water temperature sensor into the thermostat housing inlet pipe (left).


I've put together a MS Powerpoint slide for the cooling design. Existing Yamaha rubber pipes are shown in brown and new aluminium tubing shown in grey. Existing hose clips are shown in orange and new hose clips required in yellow. Pieces of silicon hose required are shown in blue.

My plumbing design is based upon black silicon hoses from Silicon Hoses . Their hoses have a 3.5mm wall thickness. I've cut the short, joining sections from the 1m lengths that they supply. I found the easiest way to cut the hoses was with a large kitchen knife (not serrated).

ID Location Description 13mm
hose clips
hose clips
hose clips
[A] Radiator (Water Pump Breather) 6mm pipe --- 6.5mm straight (50mm long) --- [T4]. 2  
[B] Radiator Outlet 25mm pipe --- 25mm 90° elbow --- [T2].   2
[C] Radiator (Thermostat Breather Inlet) 6mm pipe --- 6.5mm 45° elbow --- [T5]. 2  
[D] Radiator (Main Inlet) 25mm pipe --- 25mm 45° elbow --- [T1].   2
[E] Radiator (Oil Cooler Inlet) 14mm outlet --- 13mm 90° elbow --- [T3].  (2) 
[F] Thermostat T-Piece (Radiator) [T5] --- 6.5mm 45° elbow --- 6mm T-piece. 2  
[G] Thermostat T-piece (Thermostat) 6mm T-piece --- 6.5mm straight (50mm long) --- 6mm Thermostat (Breather Outlet). 2  
[H] Thermostat T-piece (Air Tank) 6mm pipe --- 6.5mm straight (50mm long) --- [T4]. 2  
[I] Air Catch Tank Inlet 7mm inlet --- 6.5mm 90° elbow --- [T4]. 2  
[J] Thermostat Outlet 25mm outlet --- 25mm 45° elbow --- [T1].   2
[K] T-piece (Radiator) 6mm outlet --- [H4]. 1  
[L] Water Pump Inlet 25mm inlet --- [H1].   0
[M] Water Pump Breather 6.5mm outlet --- [H2]. 1  
[N] T-piece (Water Pump Breather) 6.5mm outlet --- [H2]. 1  
[O] T-piece (Choke) 6.5mm outlet --- [H3]. 1  
[P] Head (Choke) Outlet 6.5mm outlet --- [H6] 1  
[Q] Choke (T-piece) (top) 6.5mm outlet --- [H3] 1  
[R] Choke (Head) (bottom) 6.5mm outlet --- [H2] 1  
[S] Oil Cooler (Radiator) 13mm outlet --- 13mm straight (50mm long) --- [T6].  2 
[T] Thermostat (Breather Outlet) 6mm pipe --- 6.5mm straight (50mm long) --- Thermostat T-piece. 2  
[U] Water Temp Sensor (front) 25mm outlet --- sensor housing using part of [H7]   2
[V] Water Temp Sensor (rear) 25mm outlet --- sensor housing using part of [H7]   (2)
[W] Breather pipe [T4] --- [H4] 1  
[X] Radiator inlet [H1] --- 25mm hose joiner --- 25mm 90° elbow   1
[Y] Radiator inlet 25mm 90° elbow --- [T2]   1
[Z] Radiator inlet [T6] --- [H5] --- [T3]  2 

This requires the following lengths of aluminium tubing. All aluminium tubing will be beaded.

[T1]25mm aluminium straight tube (700mm long)
[T2]25mm aluminium straight tube (800mm long)
[T3]13mm aluminium tube (280mm long).
[T4]6.5mm aluminium tube (930mm long).
[T5]6.5mm aluminium tube (750mm long).
[T6]13mm aluminium tube (400mm long).

Hose Clips

Silicon Hoses  sell a range of 'lined' clips that provide continuous band contact around the pipe and without a screw thread being in contact with the pipe (unlike the cheaper jubilee clips).


The fan is controlled automatically via the ECU, using a temperature sensor on the thermostat housing. The earlier versions of the radiator had a fan switch mounted on them. The bike has just one sender in the radiator, which the ECU uses for analogue temperature and to control the fan. For piece of mind, I'm including a fan sense wire to an LED on the dash, so I can see that/when the fan is coming on. Since I'm going to have to extend the wiring to the fan, the junctions are an ideal point to add the sense wire.


Richard  and Chris  both filled their cars with Red Line Water Wetter  to improve cooling. It seems to work well so I have bought a 355ml bottle (which will treat 15 litres of coolant and equates to a ~2.5% mix ratio) for about 20. Water Wetter doesn't do anything to raise the freezing point so anti-freeze is still required. The R1 engine has a convenient drain plug at the lowest point.

The R1 cooling system is 2.45L in capacity. With the additional pipework, I estimate it to be about 3L in total, so for a 50:50 mix I've used 1.5L of antifreeze.

I'm using the Yamaha Yamalube coolant as it is silicate and boric free.

Other Ideas

The thermostat housing is normally mounted to the engine block. This picture shows how Richard  mounted the thermostat housing. The 2003 housing is different as it has a temperature sensor and different style bolts holding it together.

It is actually simpler on the 2003 engine to leave the thermostat housing in place. By doing this I can re-use all of the existing pipe work (head to choke, choke to inlet, etc.), except the bits that connect to the radiator.

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