O-Ring For Needle Adjuster 512317

[DJT]

Does anyone know the dimensions for the above part? Mine are leaking and it seems a shame to have to order just these when I have boxes of imperial and metric o-rings in my garage.

[jbuckl]

I will measure when I get home & find the spares…. Or can post you two

[dasadrew]

I will measure when I get home & find the spares…. Or can post you two

Would be good to get the correct size if you or Dave can measure. I'd bought some once from a major supplier and had carb grief. They'd seemingly selected the "Nearest Metric Equivalent" for what was probably an imperial size.

[sujitroy]

I have a few, here . 3/8" OD . 1/16" diameter. I can't measure the ID well but it seems to be 1/4" ID

Sujit

[sujitroy]

I found t his:

https://www.isteamj.shop/index.php?main_page=product_info&products_id=259734

[Rod1883]

When I replaced mine last year I was advised by Southern Carburettors in Crawley to buy the screw and o-ring assembly as the needle adjusting screw can get damaged during removal, as can the new o-ring whilst fitting to the old screw. Screw and O-ring assembly Part number - B20042.

[richardthestag]

The only bits of the adjuster that might get damaged on removal are the thread that the needle screws onto. Normally can be recovered quite easily as the adjuster is soft.

The groove that the o-ring sits in can be deformed and again is easy to straighten out.

O-rings - I have a box of them and keep trying until I find one that fits in the groove and is also a snug fit in the tube. no idea what size it is though

The big gotcha here is that the o-ring gets damaged when pushed into place by the score marks left by the star washer the last time it was removed. I have a small fine round file which i very carefully clean up the inner edge with

[jbuckl]

Forgot by the time I was home did find this FB8C9CF7-4A82-42A3-BFB0-78386BAABE2E.png

[DJT]

Forgot by the time I was home did find this FB8C9CF7-4A82-42A3-BFB0-78386BAABE2E.png

Thanks Julian,

Those measurements correspond to #5 in my box of Imperial o-rings - 0.070" x 0.37" x 0.239"

[jbuckl]

Good stuff. And now there’s a record here… although I struggle with searching here!

[jbuckl]

Question though… how do you fit the star washer without scratches?

[Rod1883]

When I did mine last April, in addition to all the great advice I was given on this forum, I found one piece of advice on a MG forum that provided a great tip for removing the star washer - Alternative Zenith Carb Damper O-Ring Replacement : How-To Library : The MG Experience
Essentially it is to knock the adjusting screw assembly and washer up the tube just enough to then be able to get a small hooked piece of wire around the washer and flip it. I did this on both carbs and the washer just fell out. Replacement is similar - drop the washer in, shake the air valve a little to get the washer more or less in the correct orientation, and then tap home. I couldn't find a suitable wooden dowel for the job - but an unsharpened pencil (i.e. still squared off at both ends) did the job.
Doing it this way seemed to avoid any scratching of the inside of the tube.

[richardthestag]

Question though… how do you fit the star washer without scratches?

you don't need to worry about fitting it back in, the o-ring and adjuster go in first and the star washer follows. Best fit the 2 together and then use a 1/4" socket ext to tap the whole shebang into place

The scratches on installation are inevitable

[jbuckl]

you don't need to worry about fitting it back in, the o-ring and adjuster go in first and the star washer follows. Best fit the 2 together and then use a 1/4" socket ext to tap the whole shebang into place

The scratches on installation are inevitable

I can’t imagine a way that won’t scratch. Unless it’s left out.

[MikeParker]

I can’t imagine a way that won’t scratch. Unless it’s left out.

I overhauled my Stroms recently and found they did not have star washers. They never have as far as I am aware as I certainly have changed the O-rings over the years. They are like this now, and as many have said, I am worried about fitting a star washer as it may scratch the bore. I was thinking of turning up a 2-3mm long nylon "washer" that would be a tight fit in the bore. Has anyone tried this? It clearly does not need a lot to hold the needle in place as I have relied on the o-ring alone!