Misc: Everything Else New Carbs

[Monkeypants]

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

 

[Monkeypants]

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

Martyn, at this point 40,000 miles probably is forever

 

[Martyn Goodwin]

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

 

[Monkeypants]

Mikuni builds carbs in zinc alloy ( monkey metal) for some types and aluminium alloy for others . The 30mm vms I have here are in the zinc alloy ( heavy). The 34s look to be aluminium alloy and are lighter than the 30s.

Glen