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Choke Bolt Size For Hs2 Carb


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#1 jor2daje

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Posted 28 July 2012 - 02:14 AM

Hey guys just wondering what size this bolt would be. My choke was very loose and it turned out that this bolt had sheared and was just sitting there. I managed to get the broken bolt out but now I need a replacement, I'm in america and it does not seem to be standard thread so I tried an m5 which looks just about perfect but does not seem to fit. If anyone knows it would be greatly appreciated.

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#2 jimnali

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Posted 28 July 2012 - 11:51 AM

This unlikely to be a metric size - more likely to be British standard whitworth (BSW). You can order a genuine replacement from the SU carb company link or perhaps give them a call for advice of the correct size/thread and any US supplier.

#3 dklawson

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Posted 28 July 2012 - 12:57 PM

There are several possible thread types it might be. Metric is not totally out of the question but would be unusual. I believe I found throttle shafts and their mating nuts were threaded M7x1. However, if the M5 bolt was too large to fit, did you try a 10-32 (#10 UNF). A final possibility is that the bolt is a #2 BA thread. BA threads are used on some of the gauges and on SU fuel pumps.

If you can get the broken part out, compare it to your M5 bolt and a 10-32 screw. If the diameter is about right but the thread pitch does not match either the metric or UNF fastener, you are likely to need the #2 BA fastener.

This gives you choices. You can contact Mini Mania, Seven, or Heritage Garage and see if they have the part. Or... you could contact British Fasteners (online) and buy a handful of #2 BA fasteners. Lastly... it's your carb. You could re-tap the shaft to use either the M5 or 10-32 fastener and buy the bolt at your hardware store.

The bigger question is... what caused the bolt to shear? Unless you were unscrewing it and the head twisted off this failure certainly should not have happened.

#4 carbon

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Posted 29 July 2012 - 06:54 PM

The Burlen SU part number to quote is AUC1426 'Bolt' : http://www.sucarb.co...l.aspx?id=25629

Are you looking for one identical to the picture above, or is it for a twin carb set-up (these have a much larger bolt head with a recess for the choke interconnector pivot)?




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