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PR: Proprietary Items Fitting Concentrics to C Rapide

SteveO

Well Known and Active Website User
VOC Member
Just a quick question. Does anyone have experience of fitting 32mm (932) Concentrics to a C Rapide and if so could you suggest jet sizes as a starting point. My inlet tracts have been opened up to 32mm (11/4") and gas flowed, hence the question. I have obtained a pair of 30mm adaptors from the VSC, so could always go with 930's and taper the adaptors from 30mm to 32mm at head end. Would this be better/make no difference?
 

timetraveller

Well Known and Active Website User
VOC Member
Alternatively you could buy ali or bronze 32 mm adaptors from me and if needed I can get them shortened. These are copies of the original Grey Flash and Black Lightning items and there are earlier photos of these on here somewhere. Outer ends can be supplied to fit push on metal to metal, push on rubber or flange fitting. What more could a boy want?
 

vibrac

Well Known and Active Website User
VOC Member
Read up on here (This forum search) about the contrary things,especially the advice about drilling out the pilot jet
 

Robert Watson

Well Known and Active Website User
VOC Member
If you do fit 32 mm carbs onto 30 mm stubs, don't taper them. If you look at old school tuning you will find that the small step helps with increasing fuel mixing as the mixture passes the step.......... Now that should set some tongues wagging!
 

Glenliman

Well Known and Active Website User
VOC Member
Goldstar technology!
Roland Pike was in on that accidental discovery.
The story goes that Roland was setting up and tuning a works Goldstar for some big race.
The apprentice was sent to retrieve a carb to fit. He mistakenly grabbed an oversized carb and Roland mistakenly fitted it. The dyno showed a good sized increase over the normal works Goldstar output. At some point they realized the had the wrong carb.
They fitted the correct carb and the power went away
They re-fitted the wrong carb, the stepped carb and the power came back. Something is going on here!
They tapered the intake stub so that the step was gone and tried the big carb. The power went away again.
So the step stayed.
It's like the bulbous bow discovery. An accident between two freighters created a bulbous bow in one and added 4 knots to its top speed.
Now all big ships sport a bulbous bow.

Glen
 

SteveO

Well Known and Active Website User
VOC Member
Good call about the step, I remember reading about this on Gold Stars (well it has got Gold Star valves in it!). I meant tapering the other (head) end of the adaptor, or does the same hold true there? Anyone any suggestions for main jets? I was thinking along the lines of Combat Commando settings to start?
 

MartynG

Well Known and Active Website User
VOC Member
Good call about the step, I remember reading about this on Gold Stars (well it has got Gold Star valves in it!). I meant tapering the other (head) end of the adaptor, or does the same hold true there? Anyone any suggestions for main jets? I was thinking along the lines of Combat Commando settings to start?
This is a good place to start http://www.performanceindian.com/VinAmalJets.html Also here is a source of 32mm manifolds http://www.performanceindian.com/VinMan.html

Martyn
 

Chris Launders

Well Known and Active Website User
VOC Member
I have twin 32mm concentrics on mine as my ports are bigger than that (ex Chris Williams bike) I cannot remember what the settings are but sometime today I will drop the front float bowl off and have a look, actually I should drain both as it look like we're not going to be able to use them for a long while.
 

highbury731

Well Known and Active Website User
VOC Member
In the past, I have seen fabricated 32mm stainless steel inlet manifolds suitable for Concentrics, on MikesIndianParts.com, tho' I didn't find them when I had a look just now.
Paul
 

SteveO

Well Known and Active Website User
VOC Member
Carbs are fitted. Tried first start up today, after a total rebuild. Started about fifth kick and ran! It even ticked over! Sourced from Surrey Cycles, their settings matched those quoted in the links from MartynG. Only problem now is I can't take it out for a road test!
 

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