Carburettor removal and replacement

Carburettor removal is relatively simple on the Twins but hard on the Triples, the reason being that the three units of the Triple's setup are interconnected. For this reason the Twins and Triple are dealt with separately as necessary.


First remove the fuel tank. Then remove both rubber carburettor intake trunks. They both pull away. If bellmouths are fitted, unscrew both. Remove any fuel pipe including the balance tube between the two units. Retain the hose clips. If the pipe has become 'hard' onto the ferrules, ease them by warming them with a piece of wet rag immersed in hot water. Drain the float chambers.

Using either the appropriate size of 'miniature' socket or a good quality screw driver, loosen each of the carburettor's fixing clamps. Do not undo the stud nuts closer to the cylinder head. Once these clamps are loose, carefully twist and ease each carburettor body off its stub mounting. At this point the carburettors will still be hanging on their throttle and choke cables (if fitted).

If you simply want to remove the carburettors from the engine unit, to enable you to tackle some other task on the engine — perhaps, even its removal — then leave the cable(s) attached to the carburettor bodies. Hang the bodies conveniently from the top frame cables. To remove the complete body from the machine by detaching the cable(s), first, to make things easy, undo the two screws which locate the throtle slide cover and carefully withdraw each slide and needle. Then release the choke cover by its fixing screw, if cable operation is used, and withdraw the choke valve. The carburettor body should now be free. An explanation is given in the Maintenance section of this book as to how to release the cable from the slide and choke. Replacement is a straight reverse procedure. Always check the time of the carburettors after replacement.

Triple s

The procedure for removing the carburettors from a Triple is very similar to that for the Twin except that you have much less room to work and the carburettors do not separate until all three are off the machine except on 1973 machines which have three separate carburettors and cables. In other words, you must remember that a special sort of 'secondary manifold' is used to mount the three units side-by-side on the engine (except for 1973 machines). This system is used not to ease fitting but to provide a stable set-up on which to synchronise the three units together. Once the fuel tank is removed, leave the interconnecting fuel lines in place. Remove the rubber intake trunking from the machine. Loosen each of the three intake clamps. Wriggle all three carburettors together and pull them off their intake studs.

If you wish to go further and remove the three-on-one unit, release the choke lever on the front left hand side down tube, under the nose of the tank. Take off the whole thing at this stage. Now release the throttle cable nipple from the pivot clamp (the one which operates all three throttle slides from one cable) above and between the centre and right hand carburettors. The whole unit should now be free with the one-into-three choke cables. The chokes can be removed as was described for the Twins.

If you wish to separate each of the three in-unit carburettors from their mounting, take a little extra care first. Not only must you undo the six alien screws which mount the carburettors to the mounting but you must also untangle the throttle mechanisms. The key part of the mechanism is fixed between the centre and right hand carburettors. It's here that the throttle stop screw is located along with the connections for the throttle cable. Remove the fuel lines. Undo, therefore, the six alien screws (two for each carburettor) on the inlet side of the 'secondary manifold'. Then on the opposite side remove the three screws which fix the cross brace (on which the throttle mechanisms operate) to each carburettor slide cover. Watch for the layout of the throttle return springs and any interconnecting mechanisms between each carburettor. Replacement follows an opposite sequence to removal.

NOTE: Dell'Orto carburettors are very expensive, replacement parts often having horrifying prices attached to them. Take real care — these are precision made instruments which will last a long time.

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