Float level height question

My float levels are correct at 7.5mm and the plugs are very sooty throughout rev range. Mixture screw has no effect on reducing the sooty plugs and jets are standard with standard air filter and exhaust. My next step would be to adjust float levels. From experience what would members recommend? Going up by 1.5mm from 7.5 mm to 9 mm or more than this?

What main jet are you using and do your carbs vent to atmosphere or into the airbox

Hi Bif,
Carbs vent to rear swingarm (see pic) Mains are 145.

One cylinder only fires from 1500 rpm with clean idle jet so need to get in and clean all passages.
Amazingly it idles very smoothly on 3 cylinders!

I have two sets of R carbs,both are VD83A
the set that vent to the airbox run 145 mains.
The set that vent to atmosphere run 125 mains.
There was a revision kit available,if yours has solid grommets fitted in the alloy plate in the picture where the two holes are,then the jets should have been swapped for 125’s at the same time as the kit was fitted

Hi Bif,
The air chamber has no holes (solid casting) for venting so this is an 85 or later part designed to vent to atmosphere. Mine is an RE so over the years someone must have changed it.
I stand corrected on the jets - they are 120/38.
Bike starts first time pulls well, idles well but plugs are very sooty and so is the exhaust.

Float height varies from 9mm on the US 85/6 model with 125 main jet to 7.5mm for the RE.
Germany,Switzerland and France have differing venturi diameters and main jets as low as 95 but use the same float height as my RF at 8.5mm.
I would be looking at a good clean and making sure all the choke plungers are operating full stroke and in sync.It could well be the choke circuit is the problem,especially if it needs little or no choke to start from cold.
Out of interest,what is the serial number on your carbs?

Hi Bif,
Thanks for the info. I will set the float height at 8.5mm and check the choke action and see how we go. The carb ID is per the photo. The bike is originally RE from France. Is the whole carb setup a later French version or taken from, say, an Australian bike?

The French didn’t get the 85 model,and the 86 uses VD85 carbs.That would suggest they have been altered at some point.
The float height however is correct at 7.5 for the carbs you have

Hi Bif,
So the correct float height for my carbs is 7.5mm even running revised airbox and 125 mains?

That is correct

Taken carbs apart and replacing float needles. I noticed that 3 valve seats are 2.4 and one is 1.6 Will this affect float height/ restrict fuel flow?

It won’t affect float height but it will alter the fuel flow,all should be 2.4