Rover Sports Register Forum

Hi, I have a 1928 Rover 10/25 with an SU carb its running very rich any idea what needle size should be a starting point as the SU carb has replaced a rather worn out Amil.
It runs well but is very rich. Any help would be great. Many thanks. Rod Brake !.

I have no experience of the 10/25 but, given that the capacity is 1200cc, I would suggest looking through the needle listings on the Burlen SU carb site for a similar size/ performance car and using the same needle. If you call them they may be able to advise. When I put the twin carbs back on my 12 I used No 4 needles, but it had been running on a single carb with a No 5 needle. With that in mind, you could try one of those as a starter. I don’t think they are very expensive. Of course, it’s the unique shape of each needle that determines the fuel progression as the Venturi opens so what may be ok at low revs isn’t necessarily suitable at mid or high revs. Trial and error I guess.

Let us know how it goes.

Tony.

Many thanks Tony, will let you know.

Another thought is, of course, to check the needle you are currently using first and take account of that when hunting through the SU carb site lists. You have to remove it from the slider and the number should be on the flat side.
Also, you don’t mention if your replacement SU has been reconditioned. If not, probably worth getting a kit from Burlen to change seals, gaskets and the jet tube. All of which could contribute to inefficient running. Again, not too expensive and easy enough to do if you clear a space to spread all the bits out. Obviously, follow the reassembly diagram that comes with the kit as there may be seals in an old carb that have disintegrated, making it less clear where the new ones go! A can of carburettor spray cleaner is useful, although I found brake and clutch cleaner was better for getting the grime out of the alloy parts but be careful not to get it on paintwork.

Tony.

Do you have any pictures of the set up?

Rgds
Mike

Mike,

Was that a question for me or Rod? Not really clear what you want pictures of.

Thanks, Tony.

Tony, It was a question for Rod, I'm not sure what type of SU is fitted. A far as I recall the Amal carbs on 10/25s are side draught.

Mike