Author Topic: AMAC carburetor  (Read 12276 times)

Offline Metziii

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AMAC carburetor
« on: June 25, 2015, 01:30:35 PM »
Hello everybody,

I own a "not british" 1928 Horex S500. But it has a Sturmey & Archer engine with a AMAC 6/011 Carb. Hope I got the right place for my post anyway...
The thing is I canīt get the engine running properly. Thatīs why Iīve started to rebuid all parts that may affect the performance.
Now I need some help with a thread. Does anybody know the dimentions of the thread marked at the pic?!

thanks in advance!

Martin

Offline mini-me

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Re: AMAC carburetor
« Reply #1 on: June 25, 2015, 07:21:31 PM »
do you need the part that fits there?

Offline cardan

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Re: AMAC carburetor
« Reply #2 on: June 26, 2015, 12:43:33 AM »

Hi Martin,

The Type 6 is an AMAL carby introduced in 1929. 6-011 isn't in my parts. I assume this number is on the mixing chamber, and in the parts list it just says "According to motor". I suppose 6-011 is the mixing chamber used by Horex.

Re the thread, you'll have to measure it yourself. Not too hard: a micrometer (or even a vernier caliper) to measure the outside diameter of the thread, and a thread gauge to measure the TPI. Both are on the list of "must have" tools.

Parts for the Type 6 should be quite easy to source.

Cheers

Leon


Offline Metziii

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Re: AMAC carburetor
« Reply #3 on: June 26, 2015, 06:58:54 AM »
@ mini-me: yes, my original part has a crack so itīs not possible to tight it up as it should be...
but I am not looking for original spare parts, all the parts I make are made of stainless. after having them nickel plated it doesīt matter 8)

@ Leon: I already did. The tread seems to be tapered but in my opinion this shoulnīt be. Got everything set at the milling machine just try to get it right at the first time. the lead looks like a 24G 3/16 7/32

Cheers Martin

Offline cardan

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Re: AMAC carburetor
« Reply #4 on: June 27, 2015, 08:03:44 AM »

Hi Martin,

Sorry I don't know what "24G 3/16 7/32" means. A typical brass-body AMAL seems to have a 1 3/8" - 24 tpi thread, but they come in different sizes.

Cheers

Leon

Offline john.k

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Re: AMAC carburetor
« Reply #5 on: June 27, 2015, 10:09:57 AM »
Looking at your pic,the thread for the top retainer ring looks a lot worse.These parts are the same size on corresponding size carbys to the end of side bowl type production,and of course they are still made today,but in pot metal,not brass.The beauty of the brass carb is that it can easily be repaired by silver soldering a new piece in ,and cutting a  new thread  .In fact yours is probably best repaired at the same time as you resleeve the worn slide bore.Regards John.

Offline Metziii

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Re: AMAC carburetor
« Reply #6 on: June 29, 2015, 06:33:44 AM »
Hi Leon,

24G = 24tpi. Thatīs whatīs on my thread gauge...
1 3/8" helps a lot. Will try that but have to fix the lathe first  >:(

@ John
the other thread at the top looks a lot better than at the bottom. Itīs just at the pic.
I donīt like to solder it because it has been soldered once. Thatīs enough. To keep everythinig original is quite important for me but cheating a little with the material. Well.... 8)  ::)

Thanks to everybody for the support will post the result after production

Martin

Offline john.k

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Re: AMAC carburetor
« Reply #7 on: June 29, 2015, 10:59:18 AM »
Resleeving both the body and the slide back to standard dimensions are essential to the correct operation of the carb,if its at all worn.If you can rock the slide in the bore at about 1/8 opening,its worn, and all the tuning in the world wont make the motor run properly.It will also have a tendency to spit back just off idle,and be hard to start.The slide should have only a few thou of clearance in the body over its entire travel.The brass carb is very easy to repair.Regards John.

Offline Metziii

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Re: AMAC carburetor
« Reply #8 on: June 29, 2015, 01:33:44 PM »
The slide will be the next step.
thanks for mention it. Tried to find out in the past how much clearance is still ok and when it is worn out.
will check that, too.
But I guess this has to be done. My slide is made of aluminum not brass. Arenīt they originally made of brass as the body?

Cheers  Martin

Offline cardan

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Re: AMAC carburetor
« Reply #9 on: June 29, 2015, 11:00:14 PM »

Yep, early ones were certainly brass.

Leon

Offline john.k

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Re: AMAC carburetor
« Reply #10 on: July 02, 2015, 10:40:45 AM »
All sidebowl carby slides were made of brass ,even in the diecast carbys into the fifties.The hardest part to repair is the inner guide that is soldered to the jetblock.In fact ,if the guide ribs have noticeable wear,its best to true them up on a machine,and make a new slide with narrower grooves and smaller ID to suit.A carby that is small bore for the capacity of the motor[ie a 1" on a 600s/v] can tolerate a lot more wear than a  1  1/4" on a sporty 500 OHV,without affecting the motor too badly.Even slight wear in a large carb will cause spitback all the time.Regards John.

Offline Metziii

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Re: AMAC carburetor
« Reply #11 on: July 02, 2015, 12:42:41 PM »
Before asking again a little explanation first:
I only have basic knowlege in that "motor stuff" and what comes with it. But with a little thinking about everything I get in easy. But with every part which goes through my hands things are getting worse the guy who owned my Horex before shouldnīd own anything tecnical...
Thatīs why maybe some of my questions sound stupid because I am not able to copy or look at something which is done or work as it should. I am glad for every little advise.
Have the oportunity to use CNC milling and turning machines, wire cutting, Zeiss measuring machine.... Everything to draw (Solid Edge) and build a complete motor from scratch. Sometimes itīs all about the little things...

back to the interesting stuff:

I am thinking about to redo the inner guide, too. But will try to do the slide first and have a go. The guide ribs are way too narrow for the slots in the slide. Will cutout the main body for a perfect fit so a new slide has to be made anyway. I donīt wanīt to make a new jetblock thats why the cutting wonīt go all the way throuh the carb. It looks like somebody has done it before but not concentric to the jetblock.
Is there a need for the same tight fit at the inside of the slide? In this case I have to cut a lot more material
Sorry for asking again...  :P
Try to get it right the first time

Cheers

Martin

Offline john.k

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Re: AMAC carburetor
« Reply #12 on: July 04, 2015, 10:40:02 AM »
Something I have thought about was heavily nickel plating the worn parts,and then machining them back to size.I downloaded an old book on electroplating written by two university of Sheffield professors ,about electroplating,and it is also possible to plate bronze,actually transfer and deposit bronze by electro-plating.I think this is a possibility worth investigating for carby restoration.Nickel can also be plated without external electric supply,and kits are available to do this.Incidentally,since Cr6 was banned ,hardchrome plating has returned to using simpler safer methods which could be done by an experimenter.A bar to amateur electroplating generally in recent years has been the difficulty of obtaining sodium cyanide. [impossibility actually,]This is a general electrolyte for most plating,if you want the plate to turn out shiny and stuck on.For instance plating copper onto steel,only works with cyanide.This is incredibly useful for old bikes ,as it allows worn crankcase bearing bores to be tight again,without sleeving.Simply plate the steel component oversize as required,and install with a renewed interference fit.Regards John.

Offline R

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Re: AMAC carburetor
« Reply #13 on: July 04, 2015, 11:49:46 PM »
Copper can also be electroplated using the acid copper technique.
This is how most heavy copper plating is done, no cyanide involved.
Useful for taking out corrosion and pock marks back to a level surface, etc.

Not sure how it would machine up though ?

Offline Metziii

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Re: AMAC carburetor
« Reply #14 on: July 07, 2015, 07:27:19 AM »
Electroplating could be an opportunity to restore fittings. But it depends on the necessary layer thickness if it can be made or not. The problem with electroplating is you will always add more nickel at the edges than to a surface area. during the nickel process surface condition change! Adding heavy nickel (more than 0.2mm = 0.0078") on a shiny polished surface it appears like sand blasted.
the parts Iīve done in the past were electroless nickel plated with 315 ĩin high phos + 120 ĩin low phos nickel. Thatīs enough for a corrosion resistant surface.
If the layer is to thick the nickel will peel off (at the edges first)
I donīt think the bonding will be good enough do mill it or put it on the lathe. probably grinding...
My biggest concern would be to get flakes of nickel into the engine when it peels off after a few years.

At work we use hardcrome to restore oversized shotgun chambers to get them back in tolerance. Layer thickness can be made up to 0.02" if necessary but machine it after is a pain in .....