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Correct fuel line part number for GS w/ monobloc ? #476342
02/09/13 7:20 pm
02/09/13 7:20 pm
Joined: Mar 2007
Posts: 1,163
Winona, MN
Swan Offline OP

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Swan  Offline OP

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Joined: Mar 2007
Posts: 1,163
Winona, MN
Help! I am trying to determine the correct BSA part number for the fuel lines running from my Gold Star's petcocks to its AMAL 389/004 carb. This should be the scrambles set up (remember my bike has an earlier and smaller cylinder head and was set up as a scrambler with an AMAL 389) and not part number 42-8022 (Clubman fuel line from tank to remote float chamber on large GP carb). Is 42-8076 the correct line? If not, what is?

[Linked Image]
Fuel line and AMAL 389/004 Monobloc carb. Overall length is 14"

The threads on the carb banjo are 1/4" British Standard Pipe thread (.520" x 19tpi). The threads on the petcock end of the line are smaller but do not conform to BSP dimensions (?) Someone lists it as "1/8" gas". I do not know what that is. The major diameter of the petcock threads are .436" x 19 tpi.

[Linked Image]
Banjo ends are 1/4" BSP

[Linked Image]
Petcock end is "1/8 " gas" (?)

I am willing to buy the line, pipes, ends, ferrules and crimper and make my own lines if need be but the "1/8" gas" size end is throwing me off. The fuel lines are the one of the last pieces I need to complete my bike. Any help is appreciated.

Thanks!


1966 Triton
1962 BSA DBD34 Gold Star
1966 Triumph Bonneville
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Re: Correct fuel line part number for GS w/ monobloc ? [Re: Swan] #476348
02/09/13 9:07 pm
02/09/13 9:07 pm
Joined: Nov 2009
Posts: 2,231
Netherlands
Peter R Offline

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Peter R  Offline

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Posts: 2,231
Netherlands
The thread on your petcock is 7/16BSF-18TPI.
1/8 BSP (or gas) should have 28 TPI.

Last edited by Peter R; 02/09/13 9:30 pm.

Peter.
1974 Commando 850
1972 Trident T150T
1961 Goldie DBD34
1969 Benelli 250 sport special
Re: Correct fuel line part number for GS w/ monobloc ? [Re: Swan] #476375
02/10/13 1:50 am
02/10/13 1:50 am
Joined: Sep 2004
Posts: 269
E
EWebster Offline
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EWebster  Offline
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E

Joined: Sep 2004
Posts: 269
Swan, that end nut is called 7/16 like Peter says and is also found on many of the push-pull taps like on A65 and lever taps on some Spitfires. Some pieces found here:

Fuel line parts

Re: Correct fuel line part number for GS w/ monobloc ? [Re: Swan] #476376
02/10/13 2:01 am
02/10/13 2:01 am
Joined: Mar 2007
Posts: 1,163
Winona, MN
Swan Offline OP

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Swan  Offline OP

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Joined: Mar 2007
Posts: 1,163
Winona, MN
Peter, I agree 7/16 BSF is .4375 diameter and 18 TPI as stated in my "Machinery's Handbook". My petcock is most definitely 19 TPI.

[Linked Image]
.4365 Major diameter (yes, I know, I need a thread micrometer)

[Linked Image]
19 TPI, not 18 TPI.

I going to dig deeper and try to find the part number for the whole lines.


1966 Triton
1962 BSA DBD34 Gold Star
1966 Triumph Bonneville
Re: Correct fuel line part number for GS w/ monobloc ? [Re: Swan] #476378
02/10/13 2:15 am
02/10/13 2:15 am
Joined: Mar 2007
Posts: 1,163
Winona, MN
Swan Offline OP

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Swan  Offline OP

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Joined: Mar 2007
Posts: 1,163
Winona, MN
Ewebster, thank you for the link to Burton Bike Bits. Here is their chart:
[Linked Image]



1966 Triton
1962 BSA DBD34 Gold Star
1966 Triumph Bonneville
Re: Correct fuel line part number for GS w/ monobloc ? [Re: Swan] #476384
02/10/13 5:27 am
02/10/13 5:27 am
Joined: Nov 2011
Posts: 4,843
U.S.
Magnetoman Offline

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Magnetoman  Offline

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U.S.
Originally Posted by Swan
I agree 7/16 BSF is .4375 diameter and 18 TPI as stated in my "Machinery's Handbook". My petcock is most definitely 19 TPI.
I don't have the answer to your question, but since you own a copy of Machinery's Handbook you know there are a very large number of threads and thread forms. However, very few of them are 19 tpi. It's worth a few minutes to check your pitch gauge. I know the leaf stamped "19" fits your thread, but about a year ago I wasted quite a while before I discovered a high quality pitch gauge I had owned for years had a leaf with the wrong number stamped on it (once I figured this out I removed just that leaf and tossed it out). So, while it says "19", it is worth a few minutes to use your calipers and calculator to check whether it really is 19. Or, if it actually is 18.

Re: Correct fuel line part number for GS w/ monobloc ? [Re: Swan] #476405
02/10/13 10:24 am
02/10/13 10:24 am
Joined: Dec 2004
Posts: 9,671
Scotland
kommando Online content
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kommando  Online Content
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Posts: 9,671
Scotland
You can use your caliper to check the TPI, align the 2 points to the thread peaks and read the dimensions. I use a magnifying glass to ensure accuracy, you can also use a thread file as a gauge but that could be mismarked too but less likely.

Re: Correct fuel line part number for GS w/ monobloc ? [Re: Swan] #476406
02/10/13 10:33 am
02/10/13 10:33 am
Joined: Nov 2009
Posts: 2,231
Netherlands
Peter R Offline

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Peter R  Offline

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Posts: 2,231
Netherlands
Swan, I have carefully checked a original BSA petcock with a thread gauge, and found out that it has indeed 19TPI.
This makes the thread indeed 1/4BSP, so my mistake , sorry for the confusion I may have caused. blush


Peter.
1974 Commando 850
1972 Trident T150T
1961 Goldie DBD34
1969 Benelli 250 sport special
Re: Correct fuel line part number for GS w/ monobloc ? [Re: Swan] #476437
02/10/13 4:37 pm
02/10/13 4:37 pm
Joined: Feb 2012
Posts: 1,273
Middle East,
Kerry W Offline
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Kerry W  Offline
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Joined: Feb 2012
Posts: 1,273
Middle East,
Nothing to hand to compare against, but I'd expect the GP style would fit. Phil Pearson makes a spot-on set. Not cheap, but good. Don't have photos handy...wifey making me spend valuable motorcycling resources on skiing holiday in rural northern Spain..


No generalisation is wholly true, not even this one.
Oliver Wendell Holmes
Re: Correct fuel line part number for GS w/ monobloc ? [Re: Swan] #476478
02/11/13 2:26 am
02/11/13 2:26 am
Joined: Mar 2007
Posts: 1,163
Winona, MN
Swan Offline OP

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Swan  Offline OP

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Joined: Mar 2007
Posts: 1,163
Winona, MN
Thanks all for chiming in, I have half the problem sorted. I still believe 42-8076 (ref. number 103, plate 13, BMS Gold Star Book) is most likely the correct part number for the flexible fuel line running from the tank to a Monobloc carb with a 1/4" BSP threaded banjo, but, rather than order it, find out I am wrong, return them and start over again, I realized I still have the two nuts and pipes in the weird size which fit my petcocks in my old fuel lines. I can clean and reuse them so I ordered a fuel line kit from eBay UK containing two 12" long, 1/2" OD, 1/4" ID fuel hoses, two 1/4" pipes and nuts (for the banjo), 4 ferrules and a crimping tool. This is cheaper than ordering two 42-8076 lines, I get to learn something new (crimping fuel lines) and have another specialty tool to add to my growing collection. Yeah! I will let you know how it works out. Thanks again.

Magnetoman and kommando, I will check my thread gauge.

Peter R, no worries, I was already confused at the start.

Kerry W., I wish I had the time (and money) to be on the slopes snowboarding.

Last edited by Swan; 02/11/13 2:30 am.

1966 Triton
1962 BSA DBD34 Gold Star
1966 Triumph Bonneville
Re: Correct fuel line part number for GS w/ monobloc ? [Re: Swan] #476547
02/11/13 7:48 pm
02/11/13 7:48 pm
Joined: Feb 2012
Posts: 1,273
Middle East,
Kerry W Offline
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Kerry W  Offline
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Joined: Feb 2012
Posts: 1,273
Middle East,
Swan...great day on the slopes..in front of the hotel fire with a drinkable Rioja wine now..

Last edited by Kerry W; 02/11/13 7:49 pm.

No generalisation is wholly true, not even this one.
Oliver Wendell Holmes
Re: Correct fuel line part number for GS w/ monobloc ? [Re: Swan] #476605
02/12/13 6:49 am
02/12/13 6:49 am
Joined: Feb 2011
Posts: 3,539
Orygone
Boomer Offline

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Boomer  Offline

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Posts: 3,539
Orygone
The BSA parts book for Gold Star says the single feed flexible fuel line is part number 65-8173. This 7 1/2" line says 65-8172.


[Linked Image]


I threaded it onto a pitcock and this is what I got. Sorry for the out of focus but the tread gauge says 18 TPI.


[Linked Image]


[Linked Image]


Boomer

Moderated by  Rich B 


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