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A65 OIF clogged pilot circuit #543263
05/15/14 5:06 am
05/15/14 5:06 am
Joined: Dec 2003
Posts: 352
Oslo Norway
P
Per B Offline OP
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Per B  Offline OP
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Oslo Norway
I have a clogged pilot circuit on one of my carburator, This carburators has treads for separate pilot jets in the back of the floatchamber. As up to now I have not been able to clean the internal pilot jet and thus i am thinking of drilling out the whole shit and install the external pilot jet since I have external pilot jets in the spares bin.

Anyone tried this modification and can advise?

The new premium Consentric includes this external pilot jet, does anyone know how these carbs look like in the pilot mixing chamber and the area originally ocupied by the stupid internal pilot jet?


best regards

Per
Goldi Clubmans
Goldi Scrambler
Rob North R3
OIF A65
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Re: A65 OIF clogged pilot circuit [Re: Per B] #543264
05/15/14 5:15 am
05/15/14 5:15 am
Joined: Nov 2009
Posts: 2,161
Netherlands
Peter R Offline

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Peter R  Offline

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Netherlands
Per, I did the same on my Commando years ago, works fine.

I drilled the jet out from the opposite side, to avoid damage to the seat of the idle screw.
I tapped a 2BA thread, and blanked the drilled hole with a shortened idle screw with O-ring.


Last edited by Peter R; 05/15/14 5:20 am. Reason: add info

Peter.
1974 Commando 850
1972 Trident T150T
1961 Goldie DBD34
1969 Benelli 250 sport special
Re: A65 OIF clogged pilot circuit [Re: Per B] #543265
05/15/14 5:47 am
05/15/14 5:47 am
Joined: Jun 2002
Posts: 9,867
Scotland
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Stuart Offline
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Hi Per,

Originally Posted By: Per B
I have a clogged pilot circuit on one of my carburator,
As up to now I have not been able to clean the internal pilot jet and thus i am thinking of drilling out the whole shit

Why? If you're going to drill, especially if you follow Peter's advice and drill the body from the jet side so you don't risk damaging the pilot screw set, why not just drill just through the body over the pilot jet so you can see to clean it? confused

If you drill with a tapping-size drill, you can then tap the hole and block it with a screw but it'll always be there if you want to check the internal pilot jet anytime. bigt Fwiw, Les Williams did this to both my T160's carbs. back in the 1980's and no problems since

Otoh, if you drill out the internal pilot jet and fit one at the float bowl, what if it doesn't work? You've got a useless carb.! eek Bear in mind that AMAL started out with pilot jets by the floatbowl but they didn't work, which is why the internal jet is where it is.

Hth.

Regards,

Re: A65 OIF clogged pilot circuit [Re: Per B] #543270
05/15/14 6:27 am
05/15/14 6:27 am
Joined: Nov 2009
Posts: 2,161
Netherlands
Peter R Offline

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I believe that the idle jet on the underside did not work well on some engines, in particular small capacity engines.
Of course I do not know how this mod will perform on a A65, but all I know is that it works ok on the Commando.


Peter.
1974 Commando 850
1972 Trident T150T
1961 Goldie DBD34
1969 Benelli 250 sport special
Re: A65 OIF clogged pilot circuit [Re: Per B] #543272
05/15/14 7:09 am
05/15/14 7:09 am
Joined: Dec 2003
Posts: 352
Oslo Norway
P
Per B Offline OP
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Per B  Offline OP
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Oslo Norway
Stuart

The issue here is that these carbies are as good as new, the bike came to the previous owner with new carbs and he never used the bike, I have only done about 1500 km on the bike in my four years of ownership. I hate to trow away a set of unworn carburators!

The carb is usless anyway as it is so why not try the drastic solution, before I fork out for a new set of carbs.

You are right the first Consentrics came with the pilot jet in the float bowl, but for the new premium carbies that Burlen launched about two to three years ago the pilot jet is again placed in the floatbowl. A friend of mine purchased premium carbies for his 1970 A65 and the bike is just perfect at any speeds and idle stable well bellow 1000rpm and is always a first or second kick starter from hot or cold. Thats enough eveidence for me that the pilot jet in the float will work on the A65's as well.

Peter
Thanks for the information do you remember what size of drill you used to drill out the pilot jet. I do have a 2BA tap at hand and some old pilot screw to modify and put in there so this will be easy fix.


Last edited by Per B; 05/15/14 7:14 am.

best regards

Per
Goldi Clubmans
Goldi Scrambler
Rob North R3
OIF A65
Re: A65 OIF clogged pilot circuit [Re: Per B] #543277
05/15/14 7:52 am
05/15/14 7:52 am
Joined: Nov 2009
Posts: 2,161
Netherlands
Peter R Offline

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Peter R  Offline

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Netherlands
Per, I do not remember exactly what size drill I used since I made this mod several years ago.
I believe it was 3mm, but I am not 100% sure.


Peter.
1974 Commando 850
1972 Trident T150T
1961 Goldie DBD34
1969 Benelli 250 sport special
Re: A65 OIF clogged pilot circuit [Re: Per B] #543283
05/15/14 8:38 am
05/15/14 8:38 am
Joined: Dec 2004
Posts: 9,326
Scotland
kommando Online content
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Scotland
Why not just clean out the current pilot jet with a 16 thou drill glued into a WD40 red tube, you take off the pilot mixture screw and the red tube allows the drill to reach the pilot jet on the other side, a few twists with the fingers and a spray of carb cleaner and its clean for another year.

Re: A65 OIF clogged pilot circuit [Re: Per B] #543285
05/15/14 8:44 am
05/15/14 8:44 am
Joined: Mar 2005
Posts: 10,130
Boston, Massachusetts
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John Healy Online content
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Boston, Massachusetts
Per B your understanding of the new Premier AMAL is totally wrong. The pilot jet in the new premier remains in the exact same location as the earlier carburetor, but now is removable. As Stuart mentioned above, the jet was moved for a reason. The problem is more noticeable on some engines than others, but overall the carburetor works much better with the pilot jet in the pressed in location of 4 stroke engines. The jet location is also addressed on the MKII, but they use two screw in locations. One for 4 stroke and one for 2 stroke.

People have been cleaning the pressed in pilot jet for years. Both of the US Triumph distributors sent a pilot jet cleaning tool to their dealers shortly after the carburetors were put on the motorcycles. It consists of a brass rod/tube and a #78 drill (.016" diameter). While not my choice, some people choose to use a guitar string which is .016" diameter, but it just pushes the blockage upstream of the fuel flow only to allow it to drift back into the jet. Using the drill, where you twirl it between your fingers, draws the blockage down stream and it is flushed out of the carburetor. One does not need to remove the carb from the bike, only remove the pilot air screw. This is a two minute operation!!!!!!!!!!!!!


Re: A65 OIF clogged pilot circuit [Re: Per B] #543292
05/15/14 9:12 am
05/15/14 9:12 am
Joined: Dec 2003
Posts: 352
Oslo Norway
P
Per B Offline OP
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Oslo Norway
John
Ok thanks for the correction, I just assumed the pilot jet was placed in the original position when it was said to be removable. Sorry.

I will have another go with a 0,40 mm drill bit and see if i can clear the blockage, if not then i go trough the blanking on the other side, and subsequently ,tap and shut with a modified air adjuster screw.

If everything fails I will drill out the jet and put the jet in the float bowl...

(I should have bought those two 30 mm Dellortos I saw on a market two weeks ago, I have Dellortos on my two Goldies and cant praise them enough)


best regards

Per
Goldi Clubmans
Goldi Scrambler
Rob North R3
OIF A65
Re: A65 OIF clogged pilot circuit [Re: Per B] #543299
05/15/14 9:55 am
05/15/14 9:55 am
Joined: Feb 2008
Posts: 4,340
New Jersey USA
Tridentman Online content

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Tridentman  Online Content

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New Jersey USA
You will be able to clear the blockage using the procedure as described by John.
I have never NOT been able to clear one.
You just have to be careful. By feel you will be able to tell when the drill bit tip is centered in the jet and you start twirling the drill bit clockwise--you are effectively drilling through the crap and reducing it to "swarf" at the same time. The sizing of the drill bit gives you the correct jet size. I always thoroughly flood the area with carb cleaner afterwards using a strong squirt from an aerosol.
HTH

Re: A65 OIF clogged pilot circuit [Re: Per B] #543313
05/15/14 11:10 am
05/15/14 11:10 am
Joined: Jun 2002
Posts: 9,867
Scotland
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Stuart Offline
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Hi Per

Originally Posted By: Per B
Peter
what size of drill you used
have a 2BA tap at hand and some old pilot screw to modify

2BA tapping drill is 4 mm. - BA thread chart.

As a possible matter of interest, when Les Williams did my T160's carbs., he blocked the newly-drilled holes with grub screws rather than cut-down air screws. If the latter are easier for you, 4 mm tapping drill is also about right for M5 thread. bigt

Hth.

Regards,

Re: A65 OIF clogged pilot circuit [Re: Per B] #543484
05/16/14 1:13 am
05/16/14 1:13 am
Joined: May 2004
Posts: 3,717
Sydney Australia
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BSA_WM20 Offline
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As no one has put the obligatory link to Bushman's carby page I will.
Please go there and read the whole article .
Every thing you need to know about Concentrics for standard BSA's is on the page, laid out with excellent diagrams and real carb cut aways to show you how things work.
Note the carb with the base cut out to show the primary air & fuel passages has been modified with a cleaning hole on the opposite side .
I for one nevre liked the idea of doing this as I use the # 78 drill method.
last time I had to buy a new one I got a packet of 20 as that was $ 4.00 dearer than a single drill.
Got some tube from a hobby shop made up 4 for myself and sold the rest on evilbay.
They all went with 20 minutes of listing ( hint for the commercial vendors on this list ).
Now once in a blue moon I find a carb that has crud in the primary mixing chamber ( space under the two tiny holes in the throat ) and the only successful way I have found of cleaning this was to punch out the brass welch plug.
There is a Tecumseh welch plug of exactly the same size that goes directly back in.


Bike Beesa
Trevor
Re: A65 OIF clogged pilot circuit [Re: Per B] #543494
05/16/14 3:44 am
05/16/14 3:44 am
Joined: Jun 2011
Posts: 52
UK
K
Keith Miller Offline
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Joined: Jun 2011
Posts: 52
UK
Per,
Go have a look at this site,http://www.jba.bc.ca/Bushmans%20Carb%20Tuning.html, I've done this conversion and can clean out my Pilot circuit quickly and on a regular basis. Haven't had a problem with the Spitfire in the last 3 years.

Ride to enjoy...

Keith.

Re: A65 OIF clogged pilot circuit [Re: Keith Miller] #543507
05/16/14 7:25 am
05/16/14 7:25 am
Joined: Feb 2007
Posts: 2,231
Atlanta, GA USA
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Semper Gumby Offline
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Atlanta, GA USA
+1 what John Healy said. I made my own tool with the drill bit and red pipit (so I can find it in my grey tool box) from can of carb cleaner.

Used it just yesterday. That and getting rid of the exhaust leaks helps keep the Thunderbolt running well.


Gaggle of BSAs
a Honda
an old BMW
and a Montesa
Parking lot Elf in training
Re: A65 OIF clogged pilot circuit [Re: Per B] #544007
05/19/14 2:54 am
05/19/14 2:54 am
Joined: Dec 2003
Posts: 352
Oslo Norway
P
Per B Offline OP
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Per B  Offline OP
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Oslo Norway
Thanks to all, problem fixed without going to drastic measures, Instead of using a ,40mmm drillbit as described above i grinddd down a welding rod in triangular form to suit the purpose. Poked it carefully trough from the pilot adjuster side, and thats it.

A friend who gave me this methode called this the bushmans or hillbilly methode, but it works. Bike is now ideling perfect steady at 800 rpm, mostely thanks to the new TriSpark ignition kit.


best regards

Per
Goldi Clubmans
Goldi Scrambler
Rob North R3
OIF A65

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