Su thread enquiry
Posted: Mon Dec 27, 2021 10:19 am
Hi, Does anyone know what thread the suction cup retaining screws are? Part number JFZ1394 in burlen catalogues. Thanks.
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Su thread enquiry
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Re: Su thread enquiry
Posted: Mon Dec 27, 2021 10:22 am
BA I'd imagine, but I don't know the size.
Re: Su thread enquiry
Posted: Mon Dec 27, 2021 11:07 am
Suction cup.....? Haven't got a Burlen catalogue. Do you mean the dash-pots? I think that they're UNC...., quite a coarse thread. I'll go and check...
Added later.... just checked on an old carb body. If it is the dash-pot retaining screws then they're 10-24 UNC(coarse). Same screws as the fuel bowl screws
Added later.... just checked on an old carb body. If it is the dash-pot retaining screws then they're 10-24 UNC(coarse). Same screws as the fuel bowl screws
Re: Su thread enquiry
Posted: Mon Dec 27, 2021 12:01 pm
Great stuff. Thanks for the replies 
Re: Su thread enquiry
Posted: Mon Dec 27, 2021 10:35 pm
I was hoping that someone would come on board and 'correct' my thread sizing - 10-24 UNC because when I inserted that size tap - a brand new one, I felt that It was a tad tight....., like I was cleaning/clearing out the thread a bit. But enough to ask myself if I had guessed it wrong. So maybe not.
Re: Su thread enquiry
Posted: Tue Dec 28, 2021 1:33 am
3/16 BSW [Whitworth]
Same 24 TPI pitch as your tap Peter, but 55° thread form and slightly smaller OD at 0.1875”
However the differences are only about +5 degrees angle and +2.5 thou OD, so 10-24 UNC should be functionally equivalent given the tolerances of a worn alloy carb body…
Same 24 TPI pitch as your tap Peter, but 55° thread form and slightly smaller OD at 0.1875”
However the differences are only about +5 degrees angle and +2.5 thou OD, so 10-24 UNC should be functionally equivalent given the tolerances of a worn alloy carb body…
Re: Su thread enquiry
Posted: Tue Dec 28, 2021 10:34 am
Appreciate that explanation Iain. Never even considered Whit! Strange choice of thread in the 60's. Regards
Re: Su thread enquiry
Posted: Tue Dec 28, 2021 11:54 am
Re: Su thread enquiry
Posted: Tue Dec 28, 2021 12:32 pm
Here are some of the notes I put together some time back
H series carbs
Dashpot to body screw: 3/16” BSW (½” long, brass or plated steel slotted cheese head)
Fast idle lever to body screw: 0BA (5.1mm tap drill)
Throttle stop and fast idle screws: 4BA (3mm tap drill)
‘W’ clamp, and throttle return spring clamp screws: 4BA
Vacuum take off (lower corner): ¼” BSF
Float bowl to body: 7/16” BSF
Main Jet retaining screw/nut to body: ½” BSP
Float bowl lid retaining screw/nut: ¼” BSF
Float bowl lid inlet: 3/8” BSP
Butterfly retaining screws: 1/8” Whitworth (¼” long)
HS Series carbs
Dashpot to body screw: 3/16” BSW
Float chamber lid retaining screw: 3/16” BSW
Throttle stop and fast idle screws: 4BA
Float chamber to body mounting bolt:
Butterfly retaining screws: 1/8” Whitworth
H series carbs
Dashpot to body screw: 3/16” BSW (½” long, brass or plated steel slotted cheese head)
Fast idle lever to body screw: 0BA (5.1mm tap drill)
Throttle stop and fast idle screws: 4BA (3mm tap drill)
‘W’ clamp, and throttle return spring clamp screws: 4BA
Vacuum take off (lower corner): ¼” BSF
Float bowl to body: 7/16” BSF
Main Jet retaining screw/nut to body: ½” BSP
Float bowl lid retaining screw/nut: ¼” BSF
Float bowl lid inlet: 3/8” BSP
Butterfly retaining screws: 1/8” Whitworth (¼” long)
HS Series carbs
Dashpot to body screw: 3/16” BSW
Float chamber lid retaining screw: 3/16” BSW
Throttle stop and fast idle screws: 4BA
Float chamber to body mounting bolt:
Butterfly retaining screws: 1/8” Whitworth
Re: Su thread enquiry
Posted: Sat Jan 01, 2022 10:43 am
Useful thread to get this info better understood.
just for fun, SU put 1/4BSF threads in the base of the non-mini fitted AUA66 fuel fumps.
just for fun, SU put 1/4BSF threads in the base of the non-mini fitted AUA66 fuel fumps.