SW5 Float Needle Heights

[zacgrief]

Evening all,

My float needle faces are quite worn causing the bowls to drip and I have one in the lathe ready to re-face. However I guess this will shorten the needle height and so raise the float/ fuel height and I will need to space the needle back to the correct height. I can use the existing dimension but I dont know if my existing needle heights are correct to give the correct fuel height.

Does anyone have the correct dimension or a good carb on the bench which they could measure for me, if only to confirm what I have is correct? It needs to be an accurate measurement if possible.

I have attached a piccy to show what dimension I am after.

I have added a second picture to show the Amal carb type, I dont know the model type but they are the needless variety.

Thanks in anticipation.

Cheers

Zac

[graeme]

Zac,
You can work out the float height of any carburettor by rigging up a fuel line to the float bowl and see what height the float needs to be to allow the miniscus of the fuel to just reach the top of the jet in the carby itself. This is easiest done by setting up the carby in a vice on the bench - much easier to eye up the jet. Then move the clip on the float needle to the required position for the correct float height - if it ends up lower than the original clip position on the needle you can pack it out with a light washer, to raise it you need to machine or file in a new clip groove.
Cheers, Graeme

[zacgrief]

Graeme,

Thanks and I can do that no problem but where on the jet is the correct height for the fuel. I have attached a few pics and my jet is counter bored with the actual metering hole at the top. If I have the fuel just below the metering hole then the fuel level is already above flooding hole on the carb body and if the fuel is at the bottom of the jet then its not even reached the float bowl.

I suspect the needles have been changed for incorrect ones and machined to fit the floats hence me trying to get the information. They also have no means for adjusting the height via clips etc so I need to adjust by spacing the float/ needle or fitting clips (which will probably be the best option).

Many thanks

Zac

[eddie]

Zac,
       I have had a look through my box of old carb spares and found some shouldered float needles. The dimensions are: major dia .125" stepped down to .100" dia to fit in the float. The dimension from the shoulder to the tip of the point is 1.050". Do these figures tie up with what you have?
     I also have the remains of a carb for a DT, but it is the type that has a needle in the slide. Now, this type has the main jet screwed into the bottom of the needle jet, whereas, from the photos, yours looks as if the main jet is screwed into the top of the needle jet. This may be one of the differences between the 2 types of carb. Having looked at  the remains of my carb, I would think the correct fuel height should be just below the top edge of the cap nut that screws onto the bottom of the carb body. At that height, the fuel should draw up through the jet OK without being high enough to flood from the air bleeds on the pilot air screw.
      Hope this is of some help,
                          Regards,
                                    Eddie.

[zacgrief]

Eddie,

Thanks, those dimensions sound about right from memory but I will check for sure later. I am on daytime kitchen repair duties for a bit!! big sigh. That also gives me confidence that my needles etc are the correct ones, but one of them has been machined in the past, I guess to put right needle face wear.

Many thanks again.

Zac