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E: Engine 1951 Comet Carburation

David Wardingley

Website User
VOC Member
Hello all,
I have a pre monobloc fitted to my comet ( series C) which gives rather an erratic tickover when it’s very warm. I would prefer to fit something more modern in the carb dept and wonder what advice members could offer. Amal concentric, Mikuni, Delortto ? I do have good results with the concentric on a Venom but that’s a different animal.
Regards.
David
 

vibrac

Well Known and Active Website User
VOC Member
Mikuni or a new original 276 but not a Concentric I have had a feast of those this last season. For instance who wants a new carb whose pilots need to be drilled out before they will tick over ? the originals may have been OK but the latest iterations ......
 

Mike 40M

Well Known and Active Website User
VOC Member
My Venom came with a Mikuni, works well. My Comet came with a Concentric with drilled pilot, also works well. One thing I've never managed to figure out is which of all Mikuni needles is best for my Honda racer. Both Mikuni VM and Amal Concentric seems to work well on a Comet. Choose the one that you can get best advice on jetting.
 

vibrac

Well Known and Active Website User
VOC Member
Allen's in UK seem to have the settings
on the mikuni sorted on Comets 2 X 32mm and 1 X 34mm and I only had to change one pilot jet on one and that was me being finicky. I have had some problems with the rubber connector I cured one by using some of Ben's BMW hose suppliers stuff it's bright blue ! But it works
 

David Wardingley

Website User
VOC Member
Hi Erik,
Certainly the new concentric works well with the Venom, I’ve just done that job.
I’ve noted also that the concentric is half the price of the Mikuni
David
 

b'knighted

Well Known and Active Website User
VOC Member
Mikuni is top feed and on my Comet would not work on reserve. It needed a head of petrol to push past the airlock above the carb.
I have used 930 concentrics on Comets and have run a pair of 928s on the Knight for decades.
 

ericg

Well Known and Active Website User
VOC Member
Hi Erik,
Certainly the new concentric works well with the Venom, I’ve just done that job.
I’ve noted also that the concentric is half the price of the Mikuni
David
They do work very well of course. And on top of this, Mik's are ugly and totally out of place on an old British Bike.
 

vibrac

Well Known and Active Website User
VOC Member
They do work very well of course. And on top of this, Mik's are ugly and totally out of place on an old British Bike.
The concentrics date from over ten years after the demise of Vincents. They match with the dying products of British industry, Commandos, Triples, etc. not Vincents. Indeed monoblocs only just scraped in, and 'ugly' is in the eye of the beholder. For a matching number bike that's striving to be accurate a new 276, for riding and performance I would go for a Mikuni.
 
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ericg

Well Known and Active Website User
VOC Member
The concentrics date from over ten years after the demise of Vincents they match with the dying products of british industry commandos triples etc not Vincents. indeed monoblocks only just scraped in and 'ugly' is in the eye of the beholder. For a matching number bike thats striving to be accurate a new 276 for riding and performance I would go for a Mikuni
New Pre Monobloc and Monobloc are available from Burlen and it's not because you've had a couple of bad experiences with probably old clapped out ones that all the new ones are crap. This year only I've fitted about 8 bikes with new Amals and not a complaint from my customers so far!
I have no car or modern bike, my only means of transport are my old Brits, they are ALL ridden intensively, rain, snow or shine with Amals, no modern clutches, disc brakes, modern forks, etc.
Performances are just what they should be for old machines.
If I'd want modern performance and behavior I'd just purchase a modern vehicle.
Ok, in my eyes Miks are very, very uglies.
 

vibrac

Well Known and Active Website User
VOC Member
I do understand where you are coming from but I dont want a 'modern vehicle' or more appropriate I already have such a thing (or two) I am happy with the basic design and characteristics of my old bikes and I enjoy non destructive modifications like electrics carburation suspension tires and ignition that only improve the rideability & reliability and like the elctric start will allow me to continue riding into my dotage. I have some 1920's machines and there is no chance of improving them much perhaps a belt drive change, an LED in the gas lamp but thats all. so there is a place for standard, but the two Phils have given us a vehicle that was made on machinery anyone nowadays has access to and were made in such a way that they can be modified, my Vincents are all non matching numbers have no historical significance and they are mine so why not? it can all be reversed to standard which in some cases is unfortunate (vinnylonglegs et al), and anyone who wants to can can put ao a hair shirt its called individual choice
 
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Nulli Secundus

Well Known and Active Website User
VOC Member
VOC Forum Moderator
I think Eric could of mentioned that for just a few quid more you can buy from the Premier range of new Amals from Burlen. They visually look the same, but the improvements made I think would remove many, if not all, of the issues you have Tim with Monoblocs and Concentrics.
 

ericg

Well Known and Active Website User
VOC Member
I think Eric could of mentioned that for just a few quid more you can buy from the Premier range of new Amals from Burlen. They visually look the same, but the improvements made I think would remove many, if not all, of the issues you have Tim with Monoblocs and Concentrics.
Yes Nulli, when they developed the Premier carbs Burlen have eliminated the main weaknesses of the Concentrics, that is relatively high wear rate of the throttle valve and body and pilot orifice almost impossible to clean out when clogged up.
As they are on the market for at least ten years now I thought everybody in our little world was aware of their existence!
Thanks anyway Nulli.
My point is that every time someone enquire about carburetor problems the ultimate solution for some seems to be: "fit Mikuni".
I just want to counteract this!
Fit a new Amal instrument since they are available (lucky us) and virtually indistinguishable from a period one. The carb problems will be cured (unless they are actually ignition ones!) and the machine will still look and perform like an old British Bike!
But this is just my opinion, in the end it's up to the owner to do what he like with his machine, of course.
 

BigEd

Well Known and Active Website User
VOC Member
VOC Forum Moderator
Yes Nulli, when they developed the Premier carbs Burlen have eliminated the main weaknesses of the Concentrics, that is relatively high wear rate of the throttle valve and body and pilot orifice almost impossible to clean out when clogged up.
As they are on the market for at least ten years now I thought everybody in our little world was aware of their existence!
Thanks anyway Nulli.
My point is that every time someone enquire about carburetor problems the ultimate solution for some seems to be: "fit Mikuni".
I just want to counteract this!
Fit a new Amal instrument since they are available (lucky us) and virtually indistinguishable from a period one. The carb problems will be cured (unless they are actually ignition ones!) and the machine will still look and perform like an old British Bike!
But this is just my opinion, in the end it's up to the owner to do what he like with his machine, of course.
Dear Eric,
I think you have missed the point regarding "period". There is no such thing as a period Concentric on a Vincent. They were never fitted on a Vincent as they were not made until after the period that Vincents were made.
 

BigEd

Well Known and Active Website User
VOC Member
VOC Forum Moderator
All of these statements are quite true, however, the Egli Vincent is considered a legitimate marque and it was delivered with Concentrics as part of the stock specifications.

David
David makes a good point, I hadn't taken Egli Vincent into account which is what Eric has. I was thinking of machines made by Vincent.
 

ericg

Well Known and Active Website User
VOC Member
Dear Eric,
I think you have missed the point regarding "period". There is no such thing as a period Concentric on a Vincent. They were never fitted on a Vincent as they were not made until after the period that Vincents were made.
Yes, I know that Eddy, even the Monoblocs are period only for the Ds.
Once again, I'm not a purist since I build and ride bitsas as well as stock machines but I try to make all of them as they would have been built during their heyday.
I love British bikes so I try to keep them British as much as I can.
 

BigEd

Well Known and Active Website User
VOC Member
VOC Forum Moderator
Yes, I know that Eddy, even the Monoblocs are period only for the Ds.
Once again, I'm not a purist since I build and ride bitsas as well as stock machines but I try to make all of them as they would have been built during their heyday.
I love British bikes so I try to keep them British as much as I can.
Not a problem Eric. They are our bikes and we fit whatever we like. I'm not bothered about originality as you would see by some of the modifications I've made to make my Rapide so that I enjoy riding it more. My priority is function before form. What does it matter what we fit to our bikes unless the owner is entering a Concours? I enjoy my Rapide as I am sure you enjoy your Egli.
 
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