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#704850 - 08/13/17 3:36 am Re: DBD Clubman w/1038 Carb [Re: Dave - North of 60]  
Joined: Dec 2016
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Belfast Bikes Offline
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Maine
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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#704853 - 08/13/17 6:52 am Re: DBD Clubman w/1038 Carb [Re: Belfast Bikes]  
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Kerry W Online content
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Kerry W  Online Content
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Middle East,
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
#704857 - 08/13/17 9:20 am Re: DBD Clubman w/1038 Carb [Re: Belfast Bikes]  
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triton thrasher Online content
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scotland
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.
#704879 - 08/13/17 3:57 pm Re: DBD Clubman w/1038 Carb [Re: triton thrasher]  
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Maine
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.

#704881 - 08/13/17 4:00 pm Re: DBD Clubman w/1038 Carb [Re: Kerry W]  
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Maine
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.
#704891 - 08/13/17 5:22 pm Re: DBD Clubman w/1038 Carb [Re: Belfast Bikes]  
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Dave - North of 60 Offline
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Yellowknife, NWT, Canada
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.

#704894 - 08/13/17 5:41 pm Re: DBD Clubman w/1038 Carb [Re: Dave - North of 60]  
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Maine
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.
#704912 - 08/13/17 9:04 pm Re: DBD Clubman w/1038 Carb [Re: Belfast Bikes]  
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Kerry W Online content
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Kerry W  Online Content
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Middle East,
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!


No generalisation is wholly true, not even this one.
Oliver Wendell Holmes
#704931 - 08/14/17 12:39 am Re: DBD Clubman w/1038 Carb [Re: Kerry W]  
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Rich B Online happy
Rich B  Online Happy



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Stone Creek OH USA
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.


Life is too short to drink cheap, bad beer.
#704934 - 08/14/17 1:18 am Re: DBD Clubman w/1038 Carb [Re: Kerry W]  
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Maine
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.

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

#704990 - 08/14/17 4:53 pm Re: DBD Clubman w/1038 Carb [Re: Belfast Bikes]  
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ToolBox Dave Online content
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Boise, Idaho USA
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]


1961 BSA DBD34 Clubman
1966 Triumph T120TT
1972 Rickman 250MX


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

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

#705003 - 08/14/17 7:22 pm Re: DBD Clubman w/1038 Carb [Re: Belfast Bikes]  
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ToolBox Dave Online content
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Boise, Idaho USA
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


#705004 - 08/14/17 7:35 pm Re: DBD Clubman w/1038 Carb [Re: Belfast Bikes]  
Joined: Dec 2010
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Don P. Offline
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Posts: 89
san jose,ca.
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

#705082 - 08/15/17 5:56 am Re: DBD Clubman w/1038 Carb [Re: Belfast Bikes]  
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Kerry W Online content
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Kerry W  Online Content
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Middle East,
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
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