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Owner's Manual

1981 Montesa Cota 248

Table of Contents


The MONTESA motorcycle which model is introduced here, do not require an excessive care for maintenance, only a minimum attention is required to insure a long and perfect serviceable time.

With the present manual we intend to guide you about that minimum care and, at the same time, to make a disclosure of some technical features of your vehicle which undoubtedly will be of utmost interest.

Motocicietas MONTESA, S.A.

All the information - both written and graphical - contended in this Manual is merely descriptive and parts and/or components of the machine herein described may change at any time.

General Description

The two-stroke monocylinder engine measures 239.3 c.c. with a bore of 69mm. and a stroke of 64mm.; and ignition is made through a flywheel magneto alternator with external H.T. coil.

The engine is seated over a frame formed by steel pipes mutual and electrically bended and welded. The open double cradle type, very resistant as well as lightweight, including a removable dural plate to protect the engine.

The front suspension is of MONTESA telescopic fork type air-spring and the rear one is of the swinging type with double acting hydraulic shock absorbers type "Hidrobag" with adjustable initial load.

The carburettor, flexibly mounted, is equipped with a 26 mm. diameter venturi tube incorporating a choke, with air induction through the polyurethane filter located under the tank in the seat area, and protected by a silencer box.

The gearbox is of six speed, in sequence, with constant mesh pinions. The speed distribution has been studied in order to perfectly adapt to trials sport and also for you to comfortably use it when going about.

The primary drive is carried out by means of helical gears.

This model as a clutch of multiple steel discs in oil bath with constant tension springs, resulting on a high performance and effectiveness.
The brakes are of internal expansion with a friction surface diameter of 110mm.

The whole vehicle, both for its line, proportions and lightness and its assembly elements, is the result of a studied and experienced creation work in the mountain motorcycle sport field.



Use fuel of not less than 96 octane-rating for the best engine performance.

Benzol should not be used as fuel as the engine is equipped with some synthetic rubber components.


Owners can, to some extent, choose the type pressure according to the terrain in which they are riding. However, the normal pressures are given below as a guide:





Kg / cm2

Lbs. Sq in

Kg / cm2

Lbs. Sq in

Front Wheel





Rear Wheel

0.35 to 0.45

5 to 6




Open the fuel tap

If the engine is cold, use the carburettor choke lever placed at the left hand side of the carburettor.

Turn the kick start lever located on the right hand side of the engine until it can be operated.

Have the throttle completely closed.

Kick the lever strongly (the action will be much more effective if you position the lever so that the piston is in its compression position).

When the engine has warmed up, raise the choke lever to its original position.


Gearbox is of 6 speeds obtained by constant mesh pinions.

Gearbox pedal is on the left side of the engine and has to be acted according to the figure hereunder



It is convenient to make the lubrication of the chain in the inner side of same, in order to do it more effectively. Use special oil for chain, or if not available, oil type SAE-40

The tension of the chain, must also be regularly controlled. For its tensioning, act as follows:


The clutch grip shall always have a clearance of 1 to 2mm. If this clearance is excessive you cannot properly de-clutch, and if it is minimal or null, it risks to slip.

Therefore, periodically it will be advisable to check this clearance and, should it is too large, it will then be necessary to tighten the cable by means of the tightener mounted to that effect at the end of the case near the handlebar or guide


Every 250Km it needs to be revised and cleaned, checking the electrodes gap. This must be of 0.5-0.6mm.

It is recommended to replace it every 1000Km, approximately.


To use the brakes with safety and efficiency, it is convenient that the respective commands have a short throw until they start to act; this is obtained by a correct regulation which enables to compensate the fret endured by the shoes. 

Rear brake, or foot brake, is tightened by means of the nut placed at the rear end of the acting cable.

To tighten the front brake, or hand brake, it is necessary to act the tightener at the end of the case, on the handlebar.

Once these rectifications have been made, it is necessary to check that the wheels can freely spin.

Periodically is convenient to oil the cam shat by the oiler located on the shoe carrier plate. Also periodically it is suitable to make out the wheels, this enabling to clean the drums, to check the condition of the brake shoes and to slightly grease all the whirling points with SAE-40 oil.


The handling of the carburettor by then owner, may consist in deobstruct and conduit of it, leaving any eventual  variation of its adjustment to the specialized shop of the MONTESA service.

The points which may easierly be obstructed are: petrol entrance filter and slow speed and main jet.

Once the carburettor is removed out from the engine, the petrol entrance filter is on the coupler of the petrol entrance to the cask of the carburettor and for its dismantling, it is needed to unscrew the fixing bolt. Remove the filtering stuff ring from its inner part and clean it most gently for not to damage it. Afterwards mount it again - most carefully.

To deobstruct or to clean the slow speed and main jet, it will be necessary to remove the carburettor from the engine. After so doing, remove the tank from the carburettor and you will gain access to the slow speed and main jet. To deobstruct them it is necessary to blow through their central hole once they are dismantled.

To effect this operation, never use either wires nor any other hard object, for they could modify or damage the little passage conduit of the carburant thereupon altering the working of the engine.

Have in mind that you must shut the entrance of the the admission pipe while the carburettor is out.


It is very important to check the perfect operation of this element periodically (After each competition), for which reason the filtering element of same should be kept clean with soap solution (do not use gasoline nor solvents as same could affect the filtering material).

Easy access to air filter is possible by lifting the tank seat unit once the two rear elastic clamps are unfastened, thus said unit pivoting at the front and its lifted position being retained by inserting a cylindrical object - bolt pencil etc in a hole provided in the front.


It is convenient to periodically verify the steering assembly, since vibrations while on working may cause a slightly loosening of it this resulting, further to an unpleasant handling, in having the ball bearings damaged.

Leaning the motorcycle so as the front wheel is lifted up and holding the low part of the fork you will be able to check the steering clearance, pulling frontwards and rearwards alternately.

If play must be corrected, and having removed the handlebars, loosen the upper flange lock nut and the closing screws of same on the suspension arms. Having done this, tighten or loosen the lock nut of the steering bearing as required.

Retighten the upper flange lock nut and the closing screws and recheck steering play. If play is not correct, these operations should be repeated.

General Features and Data




Cycle 2 Stroke   Make Bing 84
Cylinder Single   Type 12.642/0
Bore 69mm   Diffuser diameter 26mm (with starter)
Stroke 64mm   Main jet 120
Capacity 239.3cc   Low soeed jet 150
Compression Ratio 9:1   Starter jet 80


  Gas valve No. 50
Alternator flywheel MOTOPLAT   Needle 4E1
Points contact gap 0.4mm (0.0157 in)   Needle positioning Notch No. 1
Spark advance at TDC 2.5mm (0.0981in)  



  Minimum diametrical clearance - between piston & cylinder 0.045mm (0.0018in)
Bosch thermic grade 160 - 175  
Electrodes gap 0.5-0.6mm


  Maximum whipping crankshaft - ends mounted on the crankcase 0.030mm (0.0012 in)
Thread 14M(x1,25)x19   Reccomended tightening torque
Reccomended Types      




CLNY   Cylinder fixing nuts




BP-5ES   Cylinder head fixing nuts



      Crankshaft pinion nut



      Magneto Flywheel nut



      Clutch plate nut





Type By helicoidal gearings
Pinion crankshaft 20 teeth
Clutch toothed gear 64 teeth
Transmission Ratio 3.20


Number of speeds 6
Pinion Primary Secondary Ratio
1 st gear 10 teeth 30 teeth 3.000
2 nd gear 12 " 29 " 2.410
3 rd gear 15 " 26 " 1.730
4 th gear 18 " 23 " 1.277
5 th gear 22 " 19 " 0.863
6 th gear 25 " 15 " 0.600


Counter sproket 10 teeth
Toothed gear on rear hub 40 teeth
Chain (pitch) 15.875mm (5/8")
- roller diameter 10.16mm (0.400")
- face between plates 6.48mm (0.255")










Front wheel WM1/1.6





Rear Wheel WM2/1.85





Speed Diagram





Dimensions Number  


Radial (C-3 set) 25x52x15 6205/C-3  
Clutch toothed gear


Double row 17x40x17.5 3203  
Main shaft, right side


Angular interface 15x35x11 7202  
Main shaft, left side


radial 20x47x14 6204  
Secondary shaft, right side


radial 20x47x14 6204  
Secondary shaft, left side


radial 15x35x11 6202  
Front wheel


radial 17x35x10 6003RS/C3  
Rear wheel


radial 17x40x12 6203RS/C3  

General Dimensions

Tank Capacity


1.38 USA gallons


1.35 Imp gallons


95 Kg


Recommendations for Service

Although with the instructions given in this manual you can develop an adequate maintenance of the vehicle, which undoubtedly will increase its performance, nevertheless the necessary technical assistance should be forecast. It is therefore important to bear in mind the following points:

Any specialized assistance or repair must be carried out for a Montessa Service duly authorised. The Distributor in the area will inform you on the Technical services you should contact.

To guarantee a perfect running of all the different elements of the motorcycle, you should not forget that replacements must always be made with original parts of model.

When placing parts orders, always specify:

  1. Part item, east to find out in exploded sheets of this manual

  2. Motorcycle serial number marked on crankcases and frame

translation:- Use genuine "MONTESA" spare parts always

Wiring Diagram







1 Motor Castrol super TT 3% mixture
2 Gearbox Supergras 451

SAE 90

C.C USA floz GB floz Every 2 or 3 races or similar
300 10 10.5
3 Clutch & primary drive SAE 10w30 300 10 10.5
4 Front suspension Hydrol 7 200 7.1 7.3
Per leg At discretion
5 Speedometer hubgear drive Grease At discretion
6 Brake Cam

Parts Book                                   

Frame Group I

 Frame Group II

Steering & Front Suspension Group

Exploded front suspension 

Rear suspension group  

Front Wheel Group

Exploded front wheel hub


Rear wheel group

Engine group I

Engine group II

Ignition group

Carburettor group

Exploded carburettor

Clutch & primary drive group

Transmission group

Kickstarter group

Selector group

Electrical system group

Standard accessories group

Optional accessories group



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