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Re: DBD Clubman w/1038 Carb [Re: Dave - North of 60] #704850 08/13/17 3:36 am
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Belfast Bikes Offline OP
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Thank you, Dave;

I think that your jetting recommendations have been posted at Britbike previously, and that is about where I started after installing the carburetor. Through many iterations, changes, back-steps, missteps and corrections, I find that I have been working toward leaner settings on the needle jet and main jet, and a richer pilot jet. Today, I refitted my leanest available main jet (330) and shimmed the needle jet a bit higher, and it is a noticeable improvement. I have also noticed that the gauze type air filter that I am running makes the main and needle settings richer by about a jet size, compared to an open velocity stack.

More jets are on order and there will be more testing.

Last edited by Belfast Bikes; 08/13/17 4:06 pm.
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Re: DBD Clubman w/1038 Carb [Re: Belfast Bikes] #704853 08/13/17 6:52 am
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You'll know when you have the correct pilot jet size - it mixture screw will be more or less the right number of turns out and changes to its setting will be noticeable. Get this right - it then at least makes starting the bike straightforward!

Contrary to popular belief, all jets flow all the time. A little change in the pilot will add or subtract from fuel flow elsewhere in the range, though unless it's quite a big adjustment, you're probably unlikely to feel it.


No generalisation is wholly true, not even this one.
Oliver Wendell Holmes
Re: DBD Clubman w/1038 Carb [Re: Belfast Bikes] #704857 08/13/17 9:20 am
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triton thrasher Online Content
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If your "gauze type air filter" is something like this, watch out for a mixture getting richer as revs rise, at full throttle.

[Linked Image]


Amateur Loctite enthusiast.
Re: DBD Clubman w/1038 Carb [Re: triton thrasher] #704879 08/13/17 3:57 pm
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Thank you, Triton;

I have one of the K&N look-alikes, a bit more volume than the screen that you have shown but really not enough to make it "invisible" to the carburetor.

Re: DBD Clubman w/1038 Carb [Re: Kerry W] #704881 08/13/17 4:00 pm
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Yes, Kerry;

That is exactly what is happening. I change the pilot jet so that the trim screw is about a turn out, then have over richness off-idle. I change the slide cut-away for off-idle richness, then I am a bit lean on the needle ... on and on it goes.

Last edited by Belfast Bikes; 08/13/17 4:02 pm.
Re: DBD Clubman w/1038 Carb [Re: Belfast Bikes] #704891 08/13/17 5:22 pm
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Dave - North of 60 Offline
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Recall a previous 1038 (think MM post) that mentioned two different jet holders for the 1038, one of which causes the needle to foul the main jet? Maybe this could be investigated and/or someone will chime in with some knowledge on the subject.


1958 BSA DBD Gold Star Clubman
1957 BSA Gold Star - work in progress
1965 Ducati 250 Scrambler
1971 Ducati 250 Mk3
1977 Hercules GS175
1981 Ducati Mike Hailwood Replica
(long pause)
2005 KTM 450 SMR - street legal (for going to the corner store)
Re: DBD Clubman w/1038 Carb [Re: Dave - North of 60] #704894 08/13/17 5:41 pm
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Thanks, Dave;

I have the extended jet holder that matches the later, cross drilled needle jet. I am getting pretty close now to a tolerable running condition. I was not expecting that the main jet would need to be as small as it is, and was concentrating on the settings that others had settled on. I'm not sure why mine is down around 330 (or maybe even 320), but it is somewhat reassuring to learn that Velocettes run with similar jet sizes, though those are 36mm carbs, not 38.

I'm still not sure that my magneto is all that it should be, even though it has been rewound and recapped there is reason to be suspicious (cans of worms).

Last edited by Belfast Bikes; 08/13/17 5:43 pm.
Re: DBD Clubman w/1038 Carb [Re: Belfast Bikes] #704912 08/13/17 9:04 pm
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Run the main jet size the engine wants...if it's sucking hard on the jet you'll need it to be smaller! In a sort-of parallel situation, we've taken carbs of a racing Yamaha 250 2 stroke and put them on an earlier 350 and needed smaller jetting for both needle jet and main jet, even though the 350 made more power with the same carbs than the 250 had.

Incidentally, the jetting recommendations by Allen's in the UK for the Mikuni kits they sell for the BSA, are the same for both 36 and 38mm. When I asked them about this they said that the bikes made as much top end and better mid-range on the 36mm carb, but some people wanted the 38 for 'notoriety' purposes..(or words to that effect).

Try a much smaller main jet and see. My jets are all in the UK, but I hope to be there on the 20th - PM your address and I'll send you a 260 to try! And you can keep it!


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Re: DBD Clubman w/1038 Carb [Re: Kerry W] #704931 08/14/17 12:39 am
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Rich B Offline
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I tried a 1036 on my GS, couldn't get jetting to settle down, ran like crap. Well I should say it ran ok, but I was not impressed.

Switched to a 1038 and the bike was transformed. Jetting dialed in, the mid range is amazing. And seem to remember being smaller than people recommend on the main jet......310 - 320 range.

So not sure I buy a 36 works just as well as a 38. Maybe with a Mikuni or some bikes, but I would not go back to a 36 with my experience.


Never underestimate the human ability to elevate stupid to a whole new level!.
Re: DBD Clubman w/1038 Carb [Re: Kerry W] #704934 08/14/17 1:18 am
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Kerry;

Thank you, that is a kind offer. The jets are cheap and available enough that I intend to just buy a few at a time until I run out of options. I may find that the top end never entirely clears up but I am definitely headed in the right direction; now the throttle can be nursed to redline by opening the throttle slowly until reaching WOT.

Re: DBD Clubman w/1038 Carb [Re: Rich B] #704935 08/14/17 1:21 am
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Rich;

Funny, I am considering just the opposite ... thinking that with so much trouble jetting the 1038 that I will try a 1036. The port is actually closer to the smaller size.

Re: DBD Clubman w/1038 Carb [Re: Belfast Bikes] #704990 08/14/17 4:53 pm
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ToolBox Dave Offline
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All,

below are a few images of what my 1038 carb and parts look like. The parts on the left are 2-stroke and the ones on the right are 4-stroke. The 380 main jet in the picture was way to big. i will be using a 320 main to start with.

[Linked Image]
[Linked Image]
[Linked Image]
[Linked Image]

[Linked Image]

[Linked Image]

[Linked Image]

Last edited by ToolBox Dave; 01/24/18 4:58 pm.

1961 BSA DBD34 Clubman
1966 Triumph T120TT
1972 Rickman 250MX


Re: DBD Clubman w/1038 Carb [Re: ToolBox Dave] #705002 08/14/17 6:44 pm
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Dave;

That carburetor looks brand new ... and is that a 45 year old thumb print on the intake flange?

Re: DBD Clubman w/1038 Carb [Re: Belfast Bikes] #705003 08/14/17 7:22 pm
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ToolBox Dave Offline
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That would be a yes on both. The finger print is interesting in its own right. That little bit of finger oil has changed the oxidation just enough to highlight the print. The 1038 was NOS still in the box. The AMAL Box is on display in my garage. The 1038 was "Easier" to find than the NOS AMAL 1034-38 velocity stack it is pictured with. I enjoy the hunt almost as much as the build.


1961 BSA DBD34 Clubman
1966 Triumph T120TT
1972 Rickman 250MX


Re: DBD Clubman w/1038 Carb [Re: Belfast Bikes] #705004 08/14/17 7:35 pm
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Don P. Offline
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Hi,A DBD clubman recently sold on eBay with a 1038 AMAL.The seller claimed through trial and error that he got it dialed in perfectly.He was nice enough to share his
findings with me.
He started with: 3.5 slide
380 main
108 needle it did not run well with this setup
He ended with: 2.5 slide
330 main
107 needle
30 idle jet
needle clip in bottom (of 3) slot

Re: DBD Clubman w/1038 Carb [Re: Belfast Bikes] #705082 08/15/17 5:56 am
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Kerry W Offline
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That fits very closely with what I have heard (and kept notes of) from several others, in relation to 38 Mk1 and MkII Amals.


No generalisation is wholly true, not even this one.
Oliver Wendell Holmes
Re: DBD Clubman w/1038 Carb [Re: Belfast Bikes] #723121 01/24/18 4:55 pm
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ToolBox Dave Offline
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I installed the AMAL 1038 today and added a few more pictures.


1961 BSA DBD34 Clubman
1966 Triumph T120TT
1972 Rickman 250MX


Re: DBD Clubman w/1038 Carb [Re: Belfast Bikes] #723510 01/28/18 12:27 pm
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John Alexander Offline
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To me it does sound like the needle. Classic case with the DBD 34 was that some Goldie's used for racing then sold for road use would still retain a 3GP6 needle which was for megaphone use and caused a flat spot between 4 to 4,5OO which i'm sure most of you Goldie guys know.Hmmm.

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