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Misc: Everything Else New Carbs

Leonc

New Website User
Non-VOC Member
The 930 Concentrics on my C Rapide are totally worn out and due for replacement. The machine has the various internal upgrades making it more Black Shadow like.
I have two options that I am considering, upgrading to a new pair of Premiere 932's, or a new original set of 289's for a Black Shadow.
I realise that the Concentrics are cheaper and possibly more functional, but the 289's are correct and should still function well?
Does anyone have any experience with either of these and care to comment on their own real life application?
 

Robert Watson

Well Known and Active Website User
VOC Member
My A twin came with only a few bits of the required carbs, fortunately the rear float bowl which is a bit rare, was included. When I first built it I put on a pair of well used shadow carbs and they were OK but not great. I bought a pair of the new ones forgetting the requirements for the correct spec slide which I had to go back and purchase. Having said that they work very well even tho' I paid no attention to the reams written about why and how you set the front one up to run turned 90 degrees to the vertical. Go for the 289's!

Concentrics just don't look right.

Says he with 34mm flat slides on his post war Rapide!
 

Shane998

Well Known and Active Website User
VOC Member
The 930 Concentrics on my C Rapide are totally worn out and due for replacement. The machine has the various internal upgrades making it more Black Shadow like.
I have two options that I am considering, upgrading to a new pair of Premiere 932's, or a new original set of 289's for a Black Shadow.
I realise that the Concentrics are cheaper and possibly more functional, but the 289's are correct and should still function well?
Does anyone have any experience with either of these and care to comment on their own real life application?
I have new ones on my rapide Always starts hot or cold and runs fine have not done a lot of miles only rides of about an hour when I can as COVID restrictions very bad here I also always leave it on Dave Hills stand as I’ve been told they can leak on sidestand. So I’ve had no problems but I’ve also a set of new old stock concentric which I’m putting on another rapide I’m piecing together as economically as I can Good luck
 

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Monkeypants

Well Known and Active Website User
VOC Member
Premieres work very well on a Rapide.
Eddie Stevens claimed that fitting Concentrics on a Rapide would improve power and fuel economy vs the stock carbs.
The anodized slides will last forever. Are those available with 289s?
If not that would simplify the decision for me.
The anodized slide in the photo has 15,000 + miles and looks as new. Same with the carb body.


Glen
 

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Leonc

New Website User
Non-VOC Member
Premieres work very well on a Rapide.
Eddie Stevens claimed that fitting Concentrics on a Rapide would improve power and fuel economy vs the stock carbs.
The anodized slides will last forever. Are those available with 289s?
If not that would simplify the decision for me.
The anodized slide in the photo has 15,000 + miles and looks as new. Same with the carb body.


Glen
Yes that is one of the advantages with the Premieres and I do not see the 289 slides being described as anodized.
 

Martyn Goodwin

Well Known and Active Website User
VOC Member
Premieres work very well on a Rapide.
Eddie Stevens claimed that fitting Concentrics on a Rapide would improve power and fuel economy vs the stock carbs.
The anodized slides will last forever. Are those available with 289s?
If not that would simplify the decision for me.
The anodized slide in the photo has 15,000 + miles and looks as new. Same with the carb body.


Glen
after around 40,000 miles the carb body (30mm premier) shows some wear, especially in the locator groove that the 'pin' on the side of the slide travels in
 

Monkeypants

Well Known and Active Website User
VOC Member
I think 289 and 276 slides are chromed over brass sliding in brass body so still a good wear combination.
The 289s on the Burlen site look to be of the same monkey metal as Monoblocs and Concentrics are made of. I believe it's the same basic stuff as Mikuni, Keihin, Rochester and Holley carbs are all made from. There are a few versions of it. The most common name for the material is Mazak. Also called Zamak or Zamac, it's a zinc alloy that works very well for intricate die castings

It's hard to tell what material the 289 slide is, there is only 1 low quality photo on the Burlen page.

Glen
 
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Monkeypants

Well Known and Active Website User
VOC Member
The 930 Concentrics on my C Rapide are totally worn out and due for replacement. The machine has the various internal upgrades making it more Black Shadow like.
I have two options that I am considering, upgrading to a new pair of Premiere 932's, or a new original set of 289's for a Black Shadow.
I realise that the Concentrics are cheaper and possibly more functional, but the 289's are correct and should still function well?
Does anyone have any experience with either of these and care to comment on their own real life application?
If you are aiming for Black Shadow performance then all you need are the 28 mm carbs. These are very close to 1 1/8" which is the Black Shadow size.
Internally the only thing needed is 7.3 to 1 compression , or 8 to 1 for US spec.
So there is not much in performance gap between a standard Rapide and a standard Black Shadow.
The Picador testing showed 48 bhp at crank for the Black Shadow vs 45 for Rapides tested on the same dyno.
3 bhp seems about right for a bit of compression and a bit of carb. The 55 bhp number for the Shadow is perhaps a " Brochure horsepower" number, to borrow a phrase from Phil Irving.
If your bike has stock ports then it would likely be quicker with 28 mm carbs rather than 32 mm.

Glen
 
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Martyn Goodwin

Well Known and Active Website User
VOC Member
The 289s on the Burlen site look to be of the same monkey metal as Monoblocs and Concentrics are made of. I believe it's the same basic stuff as Mikuni, Keihin, Rochester and Holley carbs are all made from. There are a few versions of it. The most common name for the material is Mazak. Also called Zamak or Zamac, it's a zinc alloy that works very well for intricate die castings

It's hard to tell what material the 289 slide is, there is only 1 low quality photo on the Burlen page.

Glen
On the Mikuni web site they say the body of their VM series is aluminium
 

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