Author Topic: Concentric carbs on C bikes  (Read 181 times)

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Offline Ginge

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Concentric carbs on C bikes
« on: September 13, 2019, 07:04:27 am »
On the back of Donald’s thread in Sales/Wants is anyone running an AMAL Concentric 620 or 622 on their bike?

Throat size matches 25/32 or 7/8 closely enough.

Are the studs spaced the same to fit the barrel like the mini block?
Ginge.

Offline hampshirebiker

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Re: Concentric carbs on C bikes
« Reply #1 on: September 13, 2019, 08:15:39 am »
Fitting should be OK on the smaller carbs, but the bore is slightly larger. I think people have got Cs to run OK on the smallest Concentrics. Give me the Monobloc in preference; any day.
Postal - Liphook Hants - But just into West Sussex.

Offline timsdad

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Re: Concentric carbs on C bikes
« Reply #2 on: September 13, 2019, 08:31:10 am »
Amal carbs are all interchangeable on stud centres and I'm sure BSA would have fitted Concentrics from new on the Cs if they'd been available, just like they changed from remote-float carbs to Monoblocs.

I know it seems to go against other opinions on here, but I like Concentrics. They're reliable, un-fussy and will just keep starting and running reliably however owners keep interfering and messing about with them.


Ray
Just a motorcyclist.

Offline cornish pixie

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Re: Concentric carbs on C bikes
« Reply #3 on: September 13, 2019, 08:35:16 am »
Morning all
I have a 622 on my Ariel Colt, works a treat, I think I had to tweak the throttle cable but otherwise fitted straight on.

Regards Martin
here in sunny cornwall

Offline cornish pixie

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Re: Concentric carbs on C bikes
« Reply #4 on: September 13, 2019, 12:45:23 pm »
A picture to prove it fits. Check the jets mine had a 105 needle jet in it.
Regards Martin
here in sunny cornwall

Offline ianinglis

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Re: Concentric carbs on C bikes
« Reply #5 on: September 13, 2019, 03:30:07 pm »
i had one on my C10L and after only 5000 miles it was worn out
i agree with dave - it now has a 375 monoblock



ian
BSA C10L 1956 - JFO 588
BSA C10L 1954 - MVE 107
RM6 RALEIGH RUNABOUT
ENFIELD DIESEL KUBOTA OC 95
BSA M21 RIGID RKN 816
CBF 1000
BSA ARIEL 3

Offline griff

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Re: Concentric carbs on C bikes
« Reply #6 on: September 13, 2019, 06:59:23 pm »
I have a few bikes on concentric carbs and no problems. Then again they are not doing high mileage.. Cheap and cheerful carb but my better bikes have monobloc carbs...    ::)   Griff
Ride safely and no pinchmarks on the seat.
 Feet-up, only on trials sections...

Offline stev60

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Re: Concentric carbs on C bikes
« Reply #7 on: September 13, 2019, 09:24:10 pm »
Ive got 622 concentrics on both C10 and C11 both run perfectly, use a spacer and upped the main jet size to 120 from memory.

Offline stev60

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Re: Concentric carbs on C bikes
« Reply #8 on: September 13, 2019, 09:31:31 pm »
Just to add every bike is different, and getting the right cutaway makes a big difference , amal do have a recommended size. once right they dont need to be touched. Both first kick starters and plug colour is spot on. 

Offline timsdad

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Re: Concentric carbs on C bikes
« Reply #9 on: Yesterday at 08:30:57 am »
I have run Concentric carbs on bikes since the '60s when they came out and, in contrast to others, I have never, ever, had to replace one of these Amals because it was worn out. Even with open bellmouths, they just keep starting and running reliably year after year after year. On odd occasions I've had to clean up a slide and body with a bit of 800g to get them to drop cleanly with a clunk but even my jets never get worn enough to be noticeable.

My '66 Triumph twin must have had a Monobloc from new but it had its 930 Concentric fitted by a previous owner and this carb has now done 56,000 miles since I've had it plus whatever the previous owner did. I really don't know what you blokes do with your carbs to warrant their replacement - you must all live in a windy desert!


Ray
Just a motorcyclist.

Offline Ginge

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Re: Concentric carbs on C bikes
« Reply #10 on: Yesterday at 08:35:46 am »
My experience is the same Ray.

They look the part, have good spares back up and they’re cheap.  Also simple.

My 375 is getting tired and leaky so I’m thinking about changing it. I have more Concentric bits than Monoblock.
Ginge.

Offline timsdad

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Re: Concentric carbs on C bikes
« Reply #11 on: Yesterday at 11:19:25 am »
Yes, Ginge, I've built up many Concentrics over the years by mixing and matching parts. I buy new seals and gaskets from Amal, plus odd jets if I haven't the correct one on the shelf, but otherwise they just keep on going.

I think the main problem is lack of use, previous owners' butchery and, occasionally, fake jets that are not the size that's marked on them.


Ray
Just a motorcyclist.