Fulvia Coupe running rich

[lancialulu]

Thanks Tim, that’s very helpful. As ever you are a font of knowledge.

Regarding sooty plugs, which is a pretty good description of mine, I recently increased the size of my idle jets to 49, so that wouldn’t have helped, but is there way of making the tickover mixture leaner?

I’ll try to take the car out soon and see what the plugs look like after run at a reasonable speed. I understand the best way is to put it into neutral then turn the engine off and coast to a stop to avoid any chance of sooting up at low revs.

I’m starting to appreciate why fuel injection was invented!

You really want to eliminate the sooty plugs first!!! Before seeing if main jet is correct (it will be). Regardless of idle  jet size the mix is set at idle through the 4 idle mix screws.... Everything has to be correct (valve timing, ignition timing,  synchronization, tappets) and it is an iterative process between synch and mix.

[lancialulu]

Tim, thanks for the advice. I have added a second copper washer to the float valves, lowering them a bit and hence reducing the petrol level. This has made a big difference, the spark plugs are now perfect although it does mean I need to use the choke to start from cold. It just shows how sensitive these Solex carbs are!

On a completely different issue, the car is going in to a local tyre shop/garage for a steering alignment check using their Hunter Hawkeye Elite 3D machine. They have obtained the data for a Fulvia Coupe which is great, the alignment had previously been done by another garage after the rebuild but I had little confidence in them and the car felt worse after they had fiddled with it than before. The main issue is lack of self-centering which I understand to be the caster angle. Not that it is adjustable of course, but I would like to see all of the figures. Maybe just setting the tracking properly will help. I shall keep you posted!

I have never needed to resort to hi tech to check steering alignment. Only  adjust toe out 1-3mm (using sticks or string...). Unless you believe ther car has been in an accident and damged the chassis.

[John.Morton50]

Just to let everyone know the outcome of my adventures with the Solex carbs, it turned out to be a fundamental problem with balance between the two carbs. I (and others) had tuned the carbs by ear ie guestimating the balance through the noise of the airflow, and then trying to set the mixture controls in the normal way. This was not working, I always had two plugs fouling so I dimly became aware of the balance issue. I ended up making a manometer out of bits of a plastic level gauge following a forum thread from some motorbike guys in the US who needed to balance twin cylinder machines. The first effort was a miserable failure as the amount of suck from the engine collapsed the plastic pipe. Using rubber pipe sold for a Rothenburg manometer used for gas systems for the connection to the carbs solved this, even though the rubber pipes partially collapsed. The "U" bend bit was made from plastic pipe from B&Q which turned out to be more robust than that from the level gauge (see photo), the connections to the intake manifolds were by modified grease nipples.
The "U" bend was partially filled with engine oil. Once I got it working I very carefully tweaked the balance setting screw so that the oil stayed where it was in the U bend as the engine speed increased. I found the setting screw to be very sensitive indeed, and that the setting I had originally was way off.
Having balanced the carbs it was a doddle to set the 4 mixture control screws at between 1/4 and 1/3 of a turn each at which point the tick over was stable and the pick up smooth. Since then the car is very much better to drive with no more plug fouling.

[HBG]

On the subject of carb balancing, I recently bought a carbtune and a couple of threaded (8mm?) nipples from ebay. Made balancing between the carbs a doddle and improved the pick up from low revs. Easy and quick way to make a big difference.