Author Topic: Flooding carburtor  (Read 1321 times)

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Offline Darryl

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Flooding carburtor
« on: 22 Oct 2023 at 19:37 »
Dear Members
I am having issues with a flooding carburetor on my CW, flooding as in petrol dripping out at a fast rate from the air intake. The carburetor is a Douglas automatic, updraft with horizontal barrel slide with air flow (choke) tunnel and piston through the barrel to control the air intake, Please see picture. There is only one position on the needle for the float to attach and have cleaned needle and seat. I believe the problem to be that the float needle seal is worn and not sealing the float chamber when the chamber is full. Would anyone know what this seal is on the float needle, can it be fixed or replaced? Or do I need to hunt for another float needle with a better seal. Please see picture.  If you have any suggestions on how to fix the needle/seal or have other reasons why you think the carburetor would flood excessively, it would be most helpful and appreciated.
Thanks
Darryl

Offline EW-Ron

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Re: Flooding carburtor
« Reply #1 on: 22 Oct 2023 at 21:52 »
You have tried the obvious, and used valve grinding paste to try grinding the needle to the seat ?

The ring of new shiny metal may give some indication of where this is going ...

Offline Darryl

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Re: Flooding carburtor
« Reply #2 on: 22 Oct 2023 at 21:57 »
Ron
Thanks, for the suggestion, I will give a bit of fine past a go.
Darryl

Offline cardan

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Re: Flooding carburtor
« Reply #3 on: 23 Oct 2023 at 01:54 »
There is only one position on the needle for the float to attach and have cleaned needle and seat. I believe the problem to be that the

If the clip is not attached to the float you can put a fibre washer between the top of the float and the clip to drop the fuel level a little.

Be gentle with valve grinding paste, even fine. A metal polish like Brasso would be a little slower but more controlled.

Leon

Offline Darryl

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Re: Flooding carburtor
« Reply #4 on: 23 Oct 2023 at 19:17 »
Ron and Leon
Have tried both of your suggestions with lapping unfortunately the needle turns inside the seal so can't really get a good lapping of the seat. 
The float is attached to the needle with a pin, will try Leon other suggestion to add a small spacer between the pin and float.
Thanks
Darryl

Offline cardan

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Re: Flooding carburtor
« Reply #5 on: 24 Oct 2023 at 01:50 »
Hi Daryl,

Are you saying that the brass cone is not firmly attached to the bottom of the needle? If so, fuel could work up between the cone and the needle to contribute to the flooding. Just solder it on - soft solder would be fine but silver solder would be better (provided it hasn't previously been soft soldered).

Cheers

Leon

Offline Darryl

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Re: Flooding carburtor
« Reply #6 on: 24 Oct 2023 at 09:22 »
Leon
There is some type of seal at the bottom of the float needle, I think it may be leather but not really sure, have a look at the photo on this thread and see what you think. And yes, the seal turns on the needle.
Your help is much appreciated.
Regards
 Darryl

Offline cardan

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Re: Flooding carburtor
« Reply #7 on: 24 Oct 2023 at 10:49 »
OK - I see.

My guess is was that the needle (including the conical bit) was brass originally - all (!) carburettors were like this from 1902 until the 1960s. In the description of the the Douglas Semi Automatic Carburettor https://www.douglasmotorcycles.net/index.php?topic=7819 it says that the fuel level "is governed by a float in the orthodox manner": a float valve made from anything other than brass would be worth a comment.

Other things would probably work, but presumably brass was better than other options. I'd say that someone has fiddled with your carb - the float needle has grooves machined in it for a flat-steel spring clip, and the drilling for a pin is likely not original. If there's still a taper seat in the bottom of the fuel bowl, maybe find an Amal float needle and cut it to length? Or get someone to machine up a little brass cone and solder it onto the bottom of your needle.

Cheers

Leon

Offline Darryl

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Re: Flooding carburtor
« Reply #8 on: 24 Oct 2023 at 18:09 »
Leon
Thanks for your suggestions, I will give them a try.
Regards
Darryl


Offline eddie

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Re: Flooding carburtor
« Reply #9 on: 25 Oct 2023 at 17:34 »
Darryl,
           Whilst your petrol leak may be caused by the increased fuel height, there may also be a secondary cause. If the float and needle are rising higher, the top of the needle may be contacting the tickler button in the float chamber cap - so, keeping the needle slightly off it's seat. Try running the bike with an extra washer between the float chamber and cap.

  Regards,
               Eddie.
« Last Edit: 25 Oct 2023 at 19:57 by eddie »

Offline Hutch

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Re: Flooding carburtor
« Reply #10 on: 26 Oct 2023 at 01:21 »
Darryl,

Had a quick look in the shed and found what may (?) be an original float needle for the Douglas carby. Appears similar to the one shown in the picture douglas-carby-3.jpg that Leon posted in;

Used c1924-1926, mostly on the CW.
....
Leon

Have included some rough dimensions of it, but can take some more accurate ones if you require. Stop for clip is soldered in position and possibly shows evidence of being altered at some stage - unless Douglas were a bit slack and didn't clean off the excess solder when it was first manufactured......

Bent up Clip is 3/32" wide and has a wear mark from the float so slightly thinner at the middle.

Do any other forum members have some dimensions for comparison / confirmation that this is an original float needle?

Hope this helps!

Cheers

Hutch

Offline Hutch

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Re: Flooding carburtor
« Reply #11 on: 26 Oct 2023 at 01:42 »
Darryl,

I just noticed that the tickler on your carby looks different to one I have and looks like it is sitting in the "pressed down" position (?) -

On the original lid I have there is a spiral spring which sits in a groove inside the lid. I made one of these (along with the lid and tickler) for a spare carby  I have. It wasn't too hard to make and I can post details of what I did if you need to make one.

Cheers

Hutch
« Last Edit: 26 Oct 2023 at 01:49 by Hutch »

Offline Darryl

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Re: Flooding carburtor
« Reply #12 on: 26 Oct 2023 at 03:11 »
Eddie
Thanks for the suggestion, but it is defiantly the needle seal or seat. I removed the seat from the carburetor and place needle in it and turned upside down filled with water. The water dripped through at a fast rate. Have also tried filling the bowl with the lid off but the flooding still occurred.
Regards
Darryl 

Offline Darryl

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Re: Flooding carburtor
« Reply #13 on: 26 Oct 2023 at 03:26 »
Hutch
Would love the measurements for the cap spring and tickler. Yes, the cap is a home job that come with the bike I grove it and using an O ring to hold in place. Is there any way I can pried the needle and float from you that you have. Apologies, I am sure I know the answer but thought I had to ask.
Regards
Darryl

Offline Doug

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Re: Flooding carburtor
« Reply #14 on: 26 Oct 2023 at 03:36 »
A similar carburetor was an option on the 1934-35 ohv models. The float needle is slightly longer than the dimensions Hutch shows but I suspect other parts like the float bowl cap were the same components being used up ten years later.

-Doug

Offline Darryl

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Re: Flooding carburtor
« Reply #15 on: 27 Oct 2023 at 17:43 »
Doug
Thanks for the information.
Regards
Darryl

Offline Hutch

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Re: Flooding carburtor
« Reply #16 on: 05 Nov 2023 at 01:29 »
Darryl,

Sorry - the Douglas carby float needle and float I have are not for sale as they are destined to go on my CW.....whenever it is when I get finally get back onto that project! I may have one repro tickler spring spare tho'

Some drawings of the tickler and spring, plus approx. dimensions of the float bowl cap for the spring and tickler are below.

I did not measure the groove for the spring very accurately but it is probably not critical as long as the spiral spring is retained reliably.

The original parts that are shown in the pictures are not the ones I used to copy to make my repro's, as at that time I only had an incomplete carby and borrowed the parts from a forum member (Thanks' Tony S !). I was lucky to later pick up a complete carby at a swap meet.

Apologies in advance for a long explanation of how I made the spiral spring for the tickler :-). I'm sure there are "many ways to skin a cat" and there are possibly easier ways to do this - but this is how I did it with what I could get easily or was at hand. As usual the normal OHS caveats apply when using power and hand tools etc.

a) The original tickler spring wire is 0.92mm or about 20 SWG. It is steel and is copper plated (to resist corrosion I would gather). I used some "music" (or sometimes called "piano") wire of 1mm diameter (measured 0.98mm) as it was easy to obtain from an online hobby store in 1m lengths. (I bought some spare and as it turned out I needed the extra I bought!). There are probably a number of sources for this wire and an internet search should turn them up easily enough. I think the wire I bought was nickel plated but not 100% sure - but it has not rusted yet - a good thing as it would not be good if the wire rusted when inside the float bowl!.

b) The outer diameter of the original spring is about 7/8" and the internal diameter is 1/4". it has 6 turns.

c) I turned up a mandrel (see picture) after I guessed the shape I needed - but it took  a few iterations to find the diameter / shape that produced roughly the correct spring shape. I didn't end up getting the repro perfect but it was near enough after a few iterations to be good enough. I used some scrap stainless steel bar of unknown origins. Just about any steel will do but needs to be reasonably strong as the material is not very thick where the slot is cut (by hacksaw in my case). Mild steel is probably no-go.

d) EDIT: -part D removed whilst I review what I wrote. I do not recommend using powered tools to form the spring using the mandrel.

e) One end of the music wire is bent over and placed in the slot in the mandrel. The free end of wire is held with vice grips. Wear gloves (wire end is spiky!) and eye protection. Hold wire as taut as possible with the vice grip pliers. Wind the piano wire onto the mandrel as tightly as possible laying each turn next to the previous one and the coil will ascend the cone of the mandrel. Be careful not to let the turns overlap the previous turn. When the ramp has been ascended on the mandrel and there are a few extra turns on the larger diameter part of the mandrel.

f) The spring will relax when the tension from the vice grips is released (be careful as is may spring back a bit). The coil will no longer be a good fit on the mandrel due to the spring back, but if the mandrel is the correct size the relaxed state of the spiral spring will be roughly the correct size over the 6-7 smallest turns.

g) Trim off the bent over bit in the centre and any un-needed coils with some side cutters (watch out using small low quality cutters etc. as the wire is hard enough to damage the edge of the cutter blades) so it fits the tickler neatly. Similarly trim off the excess outer coils to size (the coil needs to be a slightly larger diameter than the recess in the cap so it is a snug fit).

h) The tickler spring is a cone rather than flat, but flattens when installed in the cap if you place the cone apex inwards toward the tickler. If the repro cone shape is a problem (i.e. too deep or too shallow), the spring can be stretched or flattened and the cone height altered. If done just the right amount the spring will turn out flat when installed in the cap with the tickler.

i) My cold forming of the spring using the music wire may not be the best method as it is not heat treated and it can be deformed fairly easily if stretched too far, but as the tickler does not move very far and there are a few turns on the coil it seems to work as well as the original from my experience so far.

If I have stuffed up any details / dimensions or you need any more info. please let me know. I will do a drawing of the cap retaining clip when I get a chance. As far as I know there is no seal on the cap and only the two little brass buttons and the flat spring is what holds it in place.


Cheers

Hutch
« Last Edit: 05 Nov 2023 at 02:48 by Hutch »

Offline Hutch

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Re: Flooding carburtor
« Reply #17 on: 05 Nov 2023 at 01:37 »
Repro tickler spring vs original.

Cheers

Hutch

Offline Darryl

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Re: Flooding carburtor
« Reply #18 on: 05 Nov 2023 at 19:10 »
Hutch
Thanks for taking the time to give all the information and detail. I would be interested in the tickler spring if you are happy to part with it. I will contact you privately to arrange.
Darryl