Size of nuts on throttle linkage

Those small nuts on various arms attached to the throttle linkage. They look like they should be 5/16 but are not. Also not 11/32. They are a tight 7 mm.

I assume they are Whitworth? What size?

I presume that you are talking about the wrench size, not the thread size? If so, a “tight 7mm” is closer to 9/32" (7.14mm) than either 5/16" or 11/32". However, I suspect that they may be a BA size. 3BA measures 7.16mm across flats, which could be a “tight 7mm”. BSF and Whitworth sizes don’t go below 8mm as far as I know.

1 Like

The pinch bolts on the SU throttle shafts and the choke rod clevises etc.are 2BA, about .1875" OD and 31.5 TPI.

wrench size as in nuts and bolts. thanks

Since 2BA nuts measure more than 8mm across flats, I wonder if we are talking about the fasteners that Bill is interested in. The description “Those small nuts on various arms attached to the throttle linkage” is not very precise. Perhaps a photo or two might help to clarify the subject of the question?

sorry for the delay .

the nuts are .323 inches across the flats and the socket that fits snug is an 8 mm not 7.

1/8 whithworth is too big

8mm (0.3175") is very close to 5/16" (0.3125). No BSW or BSF size is that small. A 2BA nut is .324" across flats. which would be snug on an 8mm wrench, so I’d assume @Clive_Wilkinson hit the nail on the head with 2BA.

OK. So what wrench do y’all use on them? There are a lot of them on a triple and the bolt head is the same size…so I need two of them and they should be tiny so I can fish them in there.

How about using a 2BA wrench. Or if you don’t want to buy one, file out a 5/16 AF wrench. You’ll only need one because the clamps are designed to hold the bolt from turning.

1 Like

I tried to copy/paste this chart and post it here but no bueno

http://www.allcap.co.uk/Conversi.htm may help