Montesa Cota 4RT

February 9, 2014 version

February 2014 update - Montesa Cota 4RT Repsol Edition 2014

So when will Honda come out with electronic fuel injection (EFI) on a dirt bike? How about in 2005 on the Montesa Cota 4RT trials bike! 


Check out the motor - is that a pretty good replica of the CRF250 X/R bottom end?

Yes, there are differences, but I'll bet they started with the CRF cases.

The top end is totally different, not even considering the EFI throttle body.


Here's a close up of the top end. Yes, that's a Keihin EFI throttle body! Notice the electronics port - that is one humongous socket.

I like where the spark plug is located - easy access!


Here are some pictures of the 2006 Cota 4RT standard model:

Rumor has it that the '07 model will be around 300cc and 150lbs.



Trail Bike Version

There are several aftermarket manufacturers making add-on seats, which allow you to ride sitting down, but the seats are so low that they wouldn't be comfortable except for short stints. There is one manufacturer that makes a full size seat with a gas tank underneath. The tank is about two liters, giving a total of over a gallon - about enough for a 50 mile ride.



Extra Fuel

You can carry an extra liter of fuel in a fork-mounted fuel container. Now we're talking over 60 mile range!

This bike is 80 pounds lighter than my CRF230F and CRF250X! I could add an Acerbis one-gallon accessory fuel tank to the forks and still not notice the weight.

80 pounds lighter!


The Repsol Replica

Here's more info about the Repsol Replica, shown at the top and bottom of the page: Similar to the championship winning machine ridden by Dougie Lampkin, Takahisa Fujinami, Marc Freixa and Laia Sanz!

Fully programmable fuel injection and ignition kit contains a special throttle body/ECU, software and connector cables.

The other features are:


Fuel Injection

I got access to an electronic copy of a manual for the Cota and found two electrical schematics. One schematic shows the complete electrical layout and the other, shown here, shows just the fuel injection related parts. Click on the picture to see a larger version.

I tried to determine what inputs the chip (ECU) is using to control the injector. I found a water temperature sensor (TW), throttle position sensor (TPS), intake air temperature sensor (Ta), and a manifold vacuum sensor (Pb). There is also a bank angle sensor which shuts down the electrical if the bike tips over. Is that cool, or what!

I could not find an O2 sensor nor an engine knock sensor.

This system is very sophisticated yet it's minimalist design is reducing chances for failures by keeping the system simple.

One thing to note is the absence of a battery. I was told by a knowledgeable dealer that during the initial kick start, the electrical system resets then starts to power the fuel pump and injector. The engine then starts running by the time you reach the end of the kick. All this on just one kick, which I was able to observe in person. This appears to me to be a very well-designed system. (See the technical article for details.)

CarlS let me know about a very good technical article on one of Honda's many web sites: Fuel Injection System for Small Engines
Here is a press release document dated August 2005 that is very informative: Montesa Cota 4RT Repsol


Fuel Injection Related Parts

Here are some parts that are sold by B&B Road and Trials in Royston, Barnsley, England.



This is a programmable ECU and throttle body that allows the basic fuel and ignition timing maps to be modified as anyone wishes. There are 5 different maps to choose from and we install the map before posting it to you. Simply return the unit back to us for any future amendments, FOC! Sold with usual HRC product liability disclaimer. In stock.

Price: £159.93 (Excluding: VAT at 17.5%)   About $330 USD.


HRC-ECU Cables Toolkit

Allows you to connect your ECU to a PC (laptop is best, practically speaking). You will need a 12v battery and the software CD. Ask for details. In stock.

Price: £122.04 (Excluding: VAT at 17.5%)   About $253 USD.

HRC-ECU Software CD

HRC software CD to allow modification of the fuelling and ignition maps. Awaiting stock.

Price: £14.93 (Excluding: VAT at 17.5%)   About $32 USD.


HRC 260 Big-Bore Kit

A special HRC item that will give you a twin-mapped ECU and a 260 cc displacement cylinder. Handlebar mounted switch allows you to select full power map or a softer de-tuned map for wet/muddy conditions. There are only 50 such examples worldwide. Kit consists of barrel, piston, camshaft, all gaskets, switch and special ECU (single map ECU not compatable) This kit will supply a serious increase in power and torque and allows the rider to select the engine performance to suit the riding conditions. Used in conjunction with a big exhaust, dedicated HRC-ECU and Titanium silencer, you will have the ultimate in currently available 4RT technology. This is as close to Dougies & Fuji's works engines as you can get!! In stock.

Price: £1,021.27 (Excluding: VAT at 17.5%)   About $2107 USD.



The good folks at lewisport usa allowed me to use some of their pictures and information for this page. Have a look at their on-line catalog to see some very exotic parts for the bikes they sell. They also have on-line new and used bike pages. The folks at US Montesa also have a wealth of information about the Cota 4RT, including an adventure bike page. For many other parts, see B&B Road and Trials in Royston, Barnsley, England.


2005 Montesa Cota 4RT Specifications
Engine Liquid cooled, 4 stroke, single cylinder, SOHC, 4 valve, 249.1cc, Bore x Stroke 76.5 X 54.2 Compression Ratio 10.5:1
Carburetor Keihin PGM-FI electronic fuel injection
Ignition Computer-controlled digital transistorized with electronic advance
Transmission 5 speed
Secondary Drive #520 Chain
Fuel Capacity 2 liters / 0.53 gal
Frame Diamond Aluminum twin spar
Front Suspension 39 mm Showa cartridge-type telescopic fork adjustable with: 22 position compression, 20 position rebound damping and spring preload. Front wheel travel: 180 mm / 7.1 inches
Rear Suspension Pro-Link with single Showa damper with 12 position adjustable rebound damping and spring preload adjustment. Real wheel travel: 170 mm / 6.7 inches
Front Brake 185 X 3.5 mm hydraulic disc with 4 piston caliper and sintered metal pads
Rear Brake 150 X 2.5 mm hydraulic disc with 4 piston caliper and sintered metal pads
Dry Weight 73.8 kg / 162.5 lbs
Overall Length 2,016 mm / 79.5 in
Overall Width 830 mm / 32.6 in
Overall Height 1,130 mm / 44.5 in
Ground Clearance 335 mm / 13.2 in
Wheelbase 1,321 mm / 52.0 in
Seat Height 650 mm / 25.5 in
Footpeg Height 385 mm / 15.2 in