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#850923 06/06/21 10:51 pm
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Hello everyone, this is my first post on a forum (any forum!) so, fingers crossed, it all goes well.

I'm lucky to own a 1965 Spitfire Hornet which has the 389/689 twin carb setup. They are now definitely pass their use by date (leaking petrol, air escaping across the slide etc) so I feel its time to swap them out for some new Concentrics. My question is - would the 928's or 930's be the best choice for my bike? I also believe I would need to change the throttle cables from the splitter to the carbs and maybe re-jet also.

I'm not overly mechanically minded but will give anything a go, so any suggestions or thoughts would be gratefully accepted.

Kind regards, Shane

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Are your carbs 1 5/32” or 1 1/8”? I don’t believe they ever made the 1 1/8” in a 689 so I’m inclined to assume they are the 1 5/32”. Closest equivalent sizes are
1 1/8” = 28mm
1 5/32”= 30mm
Your best option will be to measure the ports on your head.

I believe you may have to swap the cables but your best idea might be to compare the cable per numbers against the 1968 numbers. Ferule or threaded top adjusters will make a difference also.

A good starting point on a Concentric is a 20% smaller main jet than what was fitted into the Monobloc. It’s not a definitive jetting and you may end up changing slides etc.


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68’ A65 Lightning “clubman”
71’ A65 823 Thunderbolt (undergoing restoration)
67’ D10 sportsman (undergoing restoration)
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As a starting point, go with the 30mm Firebird setup.

http://amalcarb.co.uk/carbspec/carburettor/spares/id/4828/

You won't be far out.

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I'm using 930 Concentrics on my A65 Firebird and they seem to work well.


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1967 B44 Shooting Star
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Different head and valves on the '65 Spitfire Hornet.


1967 BSA Wasp
1967 BSA Hornet (West Coast Model)
1967 BSA Hornet (East Coast Model)
1968 BSA Firebird Scrambler
1968 BSA Spitfire Mark IV
1965 Cyclone Competition Build
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Originally Posted by Gary E
Different head and valves on the '65 Spitfire Hornet.
Are they the smaller carbs and 38mm valves Gary?


Now let’s all have a beer beerchug

68’ A65 Lightning “clubman”
71’ A65 823 Thunderbolt (undergoing restoration)
67’ D10 sportsman (undergoing restoration)
68’ D14 trials (undergoing transformation)

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Originally Posted by Allan G
Originally Posted by Gary E
Different head and valves on the '65 Spitfire Hornet.
Are they the smaller carbs and 38mm valves Gary?

They are 1-1/8" carbs using 220 main jets

'66 & '67 Hornets came with 1-5/32" carbs using 270 main jets.


1967 BSA Wasp
1967 BSA Hornet (West Coast Model)
1967 BSA Hornet (East Coast Model)
1968 BSA Firebird Scrambler
1968 BSA Spitfire Mark IV
1965 Cyclone Competition Build
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Originally Posted by Gary E
Originally Posted by Allan G
Originally Posted by Gary E
Different head and valves on the '65 Spitfire Hornet.
Are they the smaller carbs and 38mm valves Gary?

They are 1-1/8" carbs using 220 main jets

Thanks Gary, do they use the 3.5 slide like on the Lightnings or a #4?

using that 220 main jet against my math above your looking around 180 mains as a starting point. I’d order jets up to 220 as well. Though I’d recon your going to be somewhere between 180 and 200 on a Concentric.

The math was given to me by one of the agents at Burlen when I was trying to order Concentrics to fit on a 67 bonnie (that originally had 1 1/8” carbs) I’ve used the math a couple of times on bikes I’ve worked on, sold for people and it’s not known to be an issue. If the bike is other than stock you’ll be pee’ing in the wind and will have to go through the full tuning procedure.


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from AMAL ;
(also in the 66 parts book )

Carburettor for a BSA A65 Lightning & Hornet 1966-67

Product No: 389/228

Name: Carburettor for a BSA A65 Lightning & Hornet 1966-67

Ex. VAT: £172.50(Incl. VAT: £207.00 )

Availability: Low Stock (3)

Qty:ADD TO BASKET

Details

Originally Paired with a 689 Monobloc Carburettor which is not currently in manufacture.

This carburettor is built to the original specification and comes supplied with:

3 Cutaway Slide

270 Main Jet  

106 Needle jet

25 Pilot Jet

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Well, the splatfire/hornet motor i built last year came 2nd in the aussie titles,
that was running 2 30mm amals with open bell mouths and 220 mains.
Not an economy motor but very quick.
The smaller valves don't make a lot of difference to carb size.
Given that 90% of a65's with twin carbs later than 68 had 30mm carbs,
and unless you plan on riding at more than 6k most of the time, 30mm
will be fine.

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Thanks very much everyone. Lots of great advice there and if i'm reading your replies correctly, looks like the 930's might be the way to go with correct jetting and slides.

The carbs on the bike now are the 389/206 (1 1/8", stamped May 1964, 240 main jet) and the 689/228 (1 5/32", stamped Sept 1966, 250 main) so quite interesting I guess and probably not ideal but the bike does go well, if a bit rich, even with the leaks.

Anyway, they are not going to get any better so time to swap out.

Thanks again.

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Sounds like you have a complete miss match with what you currently have.

Go by what size your cylinder head is, if it’s got a 28.5mm port tat tapers to 27mm then fit the 28mm carbs. If it’s got the 29.5mm port, fit the 30mm carbs.

The bike will run fine with either but you’ll get better usable performance/tractability with the smaller carbs than the bigger ones.

My 2c


Now let’s all have a beer beerchug

68’ A65 Lightning “clubman”
71’ A65 823 Thunderbolt (undergoing restoration)
67’ D10 sportsman (undergoing restoration)
68’ D14 trials (undergoing transformation)

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Thanks Allan, I understand now and will check those port sizes asap and certainly take your advice. Cheers

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Remember Allan, the hornet has no mufflers or air filters.
180 mains will be very lean on that setup.

It's cheaper to buy a set of main jets than a set of pistons.

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Originally Posted by NickL
Remember Allan, the hornet has no mufflers or air filters.
180 mains will be very lean on that setup.

It's cheaper to buy a set of main jets than a set of pistons.

Completely agree Nick, I didn’t know the hornet didn’t come
With filters.

200 will be a good start and then jet from there.


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71’ A65 823 Thunderbolt (undergoing restoration)
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A couple of thoughts:
1) Every Hornet I have ever seen came with air filters;
2) The 389/689 combo is pretty rare and can work pretty well. I realize that new 689s are not available. If it was mine, I would consider sleeving the carbs and replacing the jets. Concentrics are pretty ubiquitous. The 389/689 combo will make your bike standout.

Ed from NJ

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The 389/206 1-1/8" 220 main jet carbs utilized 3-1/2 slides.

All '65, '66, '67 model machines (Spitfire Hornet, Cyclone Competition, both Hornets, Wasp) came with pancake air filters

The 389/689's were standard on '66 & '67 Hornets and Wasp, so not rare in my opinion. In the used market the 689's can be a bit difficult to source.

ShaneNZ, I'd be interested in the 389/206 carb when you switch to Concentrics.


1967 BSA Wasp
1967 BSA Hornet (West Coast Model)
1967 BSA Hornet (East Coast Model)
1968 BSA Firebird Scrambler
1968 BSA Spitfire Mark IV
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Originally Posted by Gary E
The 389/206 1-1/8" 220 main jet carbs utilized 3-1/2 slides.

All '65, '66, '67 model machines (Spitfire Hornet, Cyclone Competition, both Hornets, Wasp) came with pancake air filters

The 389/689's were standard on '66 & '67 Hornets and Wasp, so not rare in my opinion. In the used market the 689's can be a bit difficult to source.

ShaneNZ, I'd be interested in the 389/206 carb when you switch to Concentrics.

I hate to disagree , according to R bacon, the 650 Hornets, 389/689 were 1 5/32" , used a 270 MJ No.3 slide , 106 NJ, 25 pilot.

the figures quoted above are nearly for a 500 Wasp.

i would be inclined to get the original carbs resleeved since 689s are made of unobtanium.


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Yes, the bike has pancake filters.

I did consider the resleeve option of the current carbs (yes, they do look good on the bike) and could yet go down that track but all the advise I've had from my local BSA club and others is to go with Concentrics. Different opinions, but all valid.

Thanks for your interest Gary E. I'll keep it in mind.

I reckon I should post some pictures of the bike. Would they be acceptabe on this thread or the 'post your picture' thread?

Thanks again for all the insight and advise.

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It’s your thread Shane, post as many photos as you like.

I wouldn’t be keen on the resleeve route for the simple reason you have 2 carbs which have different choke sizes. If you got another of the correct size so you have a match pair then it might be worth doing. But if they are the 1 1/8” carb, I think you’ll find they never made that size as a 689 but I could be wrong.


Now let’s all have a beer beerchug

68’ A65 Lightning “clubman”
71’ A65 823 Thunderbolt (undergoing restoration)
67’ D10 sportsman (undergoing restoration)
68’ D14 trials (undergoing transformation)

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Originally Posted by Allan G
It’s your thread Shane, post as many photos as you like.

I wouldn’t be keen on the resleeve route for the simple reason you have 2 carbs which have different choke sizes. If you got another of the correct size so you have a match pair then it might be worth doing. But if they are the 1 1/8” carb, I think you’ll find they never made that size as a 689 but I could be wrong.

They did make 689's in 1-1/8". The Wasp has them. 689/230 is the number.


1967 BSA Wasp
1967 BSA Hornet (West Coast Model)
1967 BSA Hornet (East Coast Model)
1968 BSA Firebird Scrambler
1968 BSA Spitfire Mark IV
1965 Cyclone Competition Build
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Originally Posted by gavin eisler
Originally Posted by Gary E
The 389/206 1-1/8" 220 main jet carbs utilized 3-1/2 slides.

All '65, '66, '67 model machines (Spitfire Hornet, Cyclone Competition, both Hornets, Wasp) came with pancake air filters

The 389/689's were standard on '66 & '67 Hornets and Wasp, so not rare in my opinion. In the used market the 689's can be a bit difficult to source.

ShaneNZ, I'd be interested in the 389/206 carb when you switch to Concentrics.

I hate to disagree , according to R bacon, the 650 Hornets, 389/689 were 1 5/32" , used a 270 MJ No.3 slide , 106 NJ, 25 pilot.

the figures quoted above are nearly for a 500 Wasp.

i would be inclined to get the original carbs resleeved since 689s are made of unobtanium.
You are correct, or should I say R. Bacon is correct. The Hornets ('66 & '67) utilized 1-5/32" carbs. The numbers are 389/228 & 689/228.

The Spitfire Hornet ('65) is the machine I posted about. It utilized 1-1/8" carbs.. The number 389/206


1967 BSA Wasp
1967 BSA Hornet (West Coast Model)
1967 BSA Hornet (East Coast Model)
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1965 Cyclone Competition Build
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Originally Posted by Gary E
Originally Posted by Allan G
It’s your thread Shane, post as many photos as you like.

I wouldn’t be keen on the resleeve route for the simple reason you have 2 carbs which have different choke sizes. If you got another of the correct size so you have a match pair then it might be worth doing. But if they are the 1 1/8” carb, I think you’ll find they never made that size as a 689 but I could be wrong.

They did make 689's in 1-1/8". The Wasp has them. 689/230 is the number.

Thankyou Gary, I stand corrected. I know the 1965 Lightning’s had 2x 389’s and I don’t think Burlen ever made 689 as a 1 1/8” (but it’s been a time since I looked and now they don’t make them anymore at all - 689 that is)


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68’ A65 Lightning “clubman”
71’ A65 823 Thunderbolt (undergoing restoration)
67’ D10 sportsman (undergoing restoration)
68’ D14 trials (undergoing transformation)

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the 689 is kind of a historical footnote ,
the end of the line .
the bottom of the pork lips page
shows a number of 689 /xxx 1 1/8" carbs ... used on the above BSA s
and also some Norton's , matchless' , and AJS 's
http://porklips.org/~mason/moto/amal_specs.html
Porklips

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Ah, apologies to Gary E, he was indeed correct , I got the year wrong.


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