SU HS6 Carburetors Needle Jets Selection

[gonzo]

I'm in the process of rebuilding another set of SU HS6 carbs for my BJ7 and sourcing some parts. The original needle jets are marked "BC" which correspond with a standard jet, as opposed to lean or rich. Supplier is suggesting to replace with rich jets due to modern methanol gas. What would you suggest, standard, rich or keep the original jets? Is there a way to check the old jets for wear? Thanks!

 

[John Turney]

Many people recommend rich jets because of the ethanol now added to gas. I've tried the rich jets and the standard jets on my 3000 Mk II engine with HD8 carbs, and I haven't really noticed a difference once the mixture is set at idle. Supposedly, it really makes a difference with Tricarbs.

I would not expect much wear unless the needles have rubbed against the jets, or there have been a lot of miles. The needles have a specified diameter at each "station" on the needle. One could use a micrometer to measure the diameters and compare to the table.

 

[gonzo]

Thanks John. I'm going to check for any needle wear, and more importantly, warpage. Both carbs passed a piston drop-test and drop at same rates. Much appreciated!

 

[bdcvg]

Last winter Joe Curto rebuilt My HD8's. He also installed one step richer needles. The only difference I found was black soot on the trunk lid. I went back to standard needles.