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ET: Engine (Twin) Pilot jet


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MartynG

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With the new concentric mk1 I hope to have the best of two worlds: outlook and function.I dont like the plastic parts and plastic tubing on the Mikunis and similar carbs.The price is a little bit secundary because the carbs ,and especially the premier ones,last for years.Best regards Erik
And you can fine tune the Mk 1 concentrics with the OVR carb kit - see OVR # 69
 

Nigel Spaxman

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VOC Member
The new designed pilot jets of the concentric mk1.Erik
Eric What is the idea behind this new air screw? The old ones didn't have the holes so if you screwed it all the way in it would shut off the air, and stall the engine, but you just didn't do that. The fuel is on the other side of the carburetor.
 

erik

Well Known and Active Website User
VOC Member
Hello Nigel! Idon`t know what amal was thinking about the new design? Fact is that on the former models there was a pressed in pilot jet and it was a nightmare to dismount it because the only way was to drill it out.Then you had the problem to get all the dirt out of this part of the carb.Now it is easier to change the pilot jets.Regards Erik
 

vibrac

Well Known and Active Website User
VOC Member
I wonder about the devotion to the concentric after all it was never a Vincent original so has no originality claim and it was a product of a dying industry the earlier versions IMO were better. My experiences with concentrics have been a direct opposite to those with Mikuni . A bit like my bike collection that starts in the twenties goes to 1958 and then jumps to the eighties and on. So perhaps with carburettors. :rolleyes:
 

ericg

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VOC Member
I use Concentrics on 5 of my machines, another wears a Monobloc and all are working very, very well.
The only drawback with Concentrics was their rapid wearing out rate, this has now been fixed by Burlen with their anodized throttle valves on Premier version which on the market for several years now .
So no need to disfigure a poor Vincent (or any other British motorcycle) with an ugly and totally out of place component made for oriental machinery.
 

davidd

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VOC Member
The Concentric was introduced for the 1968 production year, so it is many years removed from Vincent production. It was introduced primarily to address the tuning problems associated with engine pulsations, problems with gravity altering the fuel delivery during cornering and the high use of air filters. You could put a filter on an earlier Amal, but the reduction in pressure in the carb bore due to the filter had to be matched with a reduction of pressure on the float bowl or there would be variations in the mixture. The concentric did this by venting the float bowl internally, to the bore.

The Mark 1-1/2 was developed by Talleres Arreche, in Spain, to whom Amal granted a license.

David
 

ClassicBiker

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VOC Member
I think the adherence to Amal stems from the fact that though Concentrics weren't ever fitted the brand, Amals, were. The fact that Mikuni VMs are preferred over Amals I find interesting as I read some time ago that the VMs were based on the Concentric design. They are so closely based that the standard for the numbering system for the jets and the cut away on the slide is the same. I have VMs fitted to my Shadow as getting spares for the original carbs was impossible, or thought to be so, when my father first rebuilt it starting in 1978. Not having much luck with getting the correct fiber washers for the originals, Mikunis were chosen because used Concentrics were the other choice, so why go from one used carb to another when new Mikunis were to be had cheaply enough and spares were readily available. I have to agree though that the quality of Concentrics was at one time questionable at best and on that point Mikunis were the better choice.
Now that spares for the original type Amals are available and are not outlandishly priced I have given serious consideration to swapping back as I have the originals in a box on a shelf.
As for Mikunis looking out of place, I don't think they look any worse or better than any other carb. With regards to their origin, if my father a veteran of 2nd Bn, The Queens's Royal Regiment (West Surrey) and WWII wasn't to bothered about their far east origin, or if he was he never let on, then I don't suppose I will be either.
Steven
 

ericg

Well Known and Active Website User
VOC Member
Can't see the point with your WWII reference, sorry. To my eyes those Mikuni carbs are as out of place as disc brakes on a Vincent.
 

ClassicBiker

Well Known and Active Website User
VOC Member
I use Concentrics on 5 of my machines, another wears a Monobloc and all are working very, very well.
The only drawback with Concentrics was their rapid wearing out rate, this has now been fixed by Burlen with their anodized throttle valves on Premier version which on the market for several years now .
So no need to disfigure a poor Vincent (or any other British motorcycle) with an ugly and totally out of place component made for oriental machinery.
Can't see the point with your WWII reference, sorry. To my eyes those Mikuni carbs are as out of place as disc brakes on a Vincent.
My point being your reference to Mikunis being out of place because of being of oriental origin had no bearing on why they should or should not be used. If a WWII veteran who fought against the Japanese Empire was not bothered by having Japanese components on his machine why are you? The suitability of a component should be based on ability to perform the task required and the quality of the item in question, not on it's region or country of origin.
I also don't find disc brakes out of place. If a rider feels that the manner in which they ride and the traffic they find finds themselves in regularly requires disc brakes to insure their safety, by all means disc brakes.
 

vibrac

Well Known and Active Website User
VOC Member
Can't see the point with your WWII reference, sorry. To my eyes those Mikuni carbs are as out of place as disc brakes on a Vincent.
Both improve so the basic real strengths of the Vincent, as for appearence you cant see em when your riding but you know they are there when you are going and I believe stopping ( I have got round to discs yet)
 

BigEd

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VOC Member
VOC Forum Moderator
Both improve so the basic real strengths of the Vincent, as for appearence you cant see em when your riding but you know they are there when you are going and I believe stopping ( I have got round to discs yet)
This thread is titled "Pilot Jet" and a Concentric was the carburettor being used. If you need to discuss what should or should not be used on a Vincent you should start a new thread.
 
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