Concentric replacement for Monobloc

Information relating to the Matchless G3 or AJS Model 16 350cc Heavyweight
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leobailey
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Concentric replacement for Monobloc

Post by leobailey »

I am coming to the end of my patience (I don't have much) with my Monobloc carb as fitted to a 1959 G3.

I run on completely standard jet sizes etc and with a host of new parts fitted, but I still get erratic starting and other problems. I am now considering purchasing a new carb to replace the existing.

I could buy a new Monobloc and hope for better results but I am leaning towards buying a new Concentric.

I have looked over quite a few posts on replacing a Monobloc with a Concentric and the range of main jet, needle and slide settings suggested is numerous.

Has anyone fitted a Concentric to a late 1950's 350 heavyweight, all advice appreciated.

I presume a 26mm Concentric as a starting point.

Leo
Mick D
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Re: Concentric replacement for Monobloc

Post by Mick D »

Hi

Are you sure all your issues are the result of the carb? you may find a new one doesn't fix all things either.

Sorry, can't help with fitting a concentric - I bought a new Monobloc, I wanted to keep things 'original'.

Regards Mick
shifter
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Re: Concentric replacement for Monobloc

Post by shifter »

My 1954 16ms starts/runs spot on with a concentric fitted, saying that I had a 1955 16ms that started and ran spot on with a Monobloc fitted
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56G80S
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Re: Concentric replacement for Monobloc

Post by 56G80S »

Just swapped a very worn Concentric for new Monobloc from the Club and it has transformed the starting, idling and smoothness of take up at low speeds.

Johnny B
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leobailey
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Re: Concentric replacement for Monobloc

Post by leobailey »

Hi Shifter

Do you know what jetting you have on your concentric :?:

Leo
shifter
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Re: Concentric replacement for Monobloc

Post by shifter »

200 main 25 pilot 105 needle Hope this helps
Kevin
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leobailey
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Re: Concentric replacement for Monobloc

Post by leobailey »

Many thanks Shifter,

Wish me luck (once I get my hands on a new carb)

Fettling carbs is not my greatest talent, so any help appreciated.

Leo
SPRIDDLER
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Re: Concentric replacement for Monobloc

Post by SPRIDDLER »

Concentric tuning guide here, Leo:

http://www.hitchcocksmotorcycles.com/pi ... ettors.pdf

Enjoy!
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Bruno
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Re: Concentric replacement for Monobloc

Post by Bruno »

Hi Leo,

I have a 1961 G3 which already had a concentric fitted when I got it. The motorcyle starts easily and idles steadily.

The carb is a 26mm bore, main jet 180, pilot jet 25 and needle jet .106.

I also have 350 Triumph which has a monobloc and it runs OK as well - if anything I feel the monobloc is easier to get into for cleaning fuel pathways, especially the pilot jet system. So I've no real complaints with either - Mick's right that the monobloc is what was originally fitted, so if you after originality stick with it.

Have you already tried getting the original monobloc professionally cleaned and overhauled before consigning it to junk?

Cheers, Bruno
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leobailey
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Re: Concentric replacement for Monobloc

Post by leobailey »

After some considerable time pondering the relative merits of Monobloc (originality) versus Concentric ( reliability ) I have order a new Mk 1 Concentric. I'll let you all know how it goes once I've fitted it.

I will put the original Monobloc with all its new bits and bobs on the shelf, you never know I may even develop a bit of patience in the future and give it another go. Although with the time /money/and fiddling I have already given the 376/5 Monobloc :headbang: , the Concentric seems the way forward

Thanks to you all for input, and Spriddler thanks for the Concentric tuning link
.
Leo

Oh and I have indicators fitted ,so the originality boat has already sailed.
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