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I need to buy some replacement O rings for the choke jet in my old 25mm carburettors. Please can you recommend the dimensions and/or the particular part number if it's not a standard, generic O ring. I'd like to buy at least 2 and ideally around 5. I'm in the UK.

Thank you, Julian.

Their only function is to hold the float bowl on whilst you fit the main jet holder.
I replace them if I'm using a complete gasket/seal kit, otherwise I just don't worry about them.

I think they are 3 x 1,8mm for all our carbs 25, 26, 28

Paul,
I'm curious about the various discussions on the forum that seem to connect poor starting or poor running with this O ring being faulty. From what you say, it sounds like you don't have those sorts of problems (or have found other causes for them...?).

I'll see if I can get a replacement anyway thanks to Norbert's response, here's hoping this bike learns to behave

Thank you

Julian

If not give it a good thrashing...? Basil Fawlty style...

The starter jet is submerged in fuel. The O-ring would seal the jet to a passageway that is submerged in fuel. Is this likely to make a difference?

Whenever someone insists that replacing the O-ring improved their starting problems, you've always got to ask, what sequence of actions did they take to replace the O-ring?

How many people are fitting a new O-ring to the starter jet without removing the caburettor and/or removing the starter jet from the carburettor?

Did they blow through the jet to remove the remaining fuel? Could simply removing the jet have disturbed a blockage?

Is it likely that any of those actions could result in the problem being fixed?

There's no downside to fitting new O-rings unless you have the attitude that...

"I can't fix my starting problem and go riding until I've obtained some new O-rings"
(or you break something whilst doing so!)


Often people are fixing problems by 'ritual' rather than by thinking through a sequence. When you're dealing with something like the ignition system that can lead to more problems being introduced along side the original one and a lot of frustration.

Eurocarb sell the O rings individually, but the postage would probably be expensive in comparison. Simplybearings sell O-rings and delivery is free.

Do you happen to know, which of the myriad options on simplybearings is the best O ring to order please? they have sizes that are close to norbert's measurements but none that match exactly e.g. this one is 1.78mm thickness by 2.9mm bore https://simplybearings.co.uk/shop/Seals ... index.html There are even 4+ choices of material for the O ring!

In the interim, by searching for the part number from Eurocarb (6173) I found they're slightly cheaper to buy from
https://www.splatshop.co.uk/dellorto-ch ... -ring.html who include VAT in their prices and charge slightly less for the P+P (£2.99 including VAT compared to £3.50 + 20% VAT)

Thanks again

The size you've found should be close enough. Nitrile will do the job

http://thisoldtractor.com/moto_guzzi_lo ... 6100-.html
And for the top:
http://thisoldtractor.com/moto_guzzi_lo ... 8300-.html

Thank you for these links.

Since the price per unit drops massively on simplybearings I've bought enough to share:

1 BS006.VIT_PK50 BS006 1.78mm Section 2.9mm Bore VITON Rubber O-Rings - Pack Size: Pack of 50 £6.92
Items Sub Total: £6.92
(Free Delivery (Ships Friday)): £0.00
VAT: £1.38
Order Total: £8.30