Solex carbys as fitted to Rolls Royce "B" series motors.
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From Richard in England comes the following article regarding rebuilding the Solex carburetor. It is taken from several replies he has made on Mil-Veh-List over a number of years.


>Does anyone have a source for the carburetor accelerator pump

Well, there's doubtless plenty over here. The Ferret uses a Solex 40 NNIP carb whilst the Solex 48 NNIP carbs is used on B80 engines - Saladin/Saracen etc, and as far as I can see from the RR Manual TSD 702 the pump diaphragms are identical to Stalwart and FV 432 B81 Solex 48 NNIP carbs, this would not be surprising as the whole engine range was designed with extreme commonality of parts for mil use. There is nothing special about these internal parts and are a common Solex part of the day.

I have no doubt one of the many mil dealers here have new ones that are readily mailable, complete new and used carbs (as I have seen by the bin load), although they'd likely want to just send a complete carb.

These are four places that will likely have something that you can email: C&C Military Services,
Marcus Glenn,
RR Motor Services, ( )

There is a particular procedure in TSD 702 for re-assembly of acc pump diaphragms to ensure full and free operation.

> Our Saracen has less power, now that we rebuilt the carb. That kinda
> makes no sense to me, unless it had been tuned to account for being
> clogged, somehow. Now that it is unclogged, the tuning ratios would be
> different, I suppose.
> ` I'd appreciate any tuning tips from people that have done this
> operation on this vehicle. Thanks. Jim


Download the big pics by clicking on the small pics...


The 40 NNIP Solex fitted to a B80 is a fixed jet carburettor with only idle mixture and throttle stop adjustment available, all other systems are fixed and "untunable".

It is quite possible to mis-assemble the instrument though, damage a fine gasket or tear an accelerator pump diaphragm by not flexing it before clamping its cover.

It has three filters, one in the inlet banjo and one below each accelerator pump.

I would minutely re-check the device for assembly faults and correct gasket placement, plus the fuel line felt filter element which can hide a multitude of sins, water and rust, service the oil bath filters and replace the oil to the level mark.

It is possible a choked carburettor was hiding other faults, this engine uses a twin point ignition system, it is entirely impossible to set the critical 45 deg angle between the points without removal and the use of a specially made jig (simple). Each set of points fires a cylinder in turn AND acts alternately as a dwell angle extension system for its mate, if the internal angle setting is wrong 4 cylinders will be mis-timed relative to the other four. You will note it is an 8 cylinder engine with a 4 lobe distributor cam and can be likened to a pair of 4 cylinder distributors on a common body firing 45 deg apart.

It is also critical that B Range engines are statically timed between 0 deg and 2 deg AFTER TDC. This cannot be done except with a static timing light as the design intentionally advances the ignition at idle speed, the setting allows for hand cranking in an emergency with no danger of a kick back. Any attempt to set the distributor with the engine running at idle by ear or with a strobe is a guaranteed disaster.

Check also that the ballast resistors are intact and that half the battery voltage (engine static) is actually available at the coil with one or the other set of points closed.

Bad rotor arms and distributor caps can also give every indication of a carb fault whilst allowing the engine to start easily having the ignition boost start with the ballast resistors by-passed during cranking.

The platinum screened plugs are readily fouled and will not self-clean no matter what the general hype about these types may lead you to believe, it is quite difficult to hear that one or two may be intermittently firing and if it has run rich during previous work then some fouling is quite possible. Have the screen unions already slackened and remove each lead in turn at idle noting any change in revs or note, there is little danger of a HT shock as the leads are screened and grounded through their sheaths.

Have the plugs grit blasted to clean and only then disassemble them to ensure no grit remains, do not ever wire brush the disassembled plug with steel or brass brushes, the platinum will either be compromised or you will leave metallic traces in the centre insulator causing tracking. Re-set to 15 thou.

We assume the rest of the engine is in acceptable order.

Southampton - England

My thanks yet again to Richard.


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