400 four main jet o ring

[ozzybud]

Is that the correct material Ozzybud?

Says NBR on the packaging and if memory serves that’s nitrile, which is not recommended for today’s fuels containing ethanol. Surely Viton or FKM would be a much better choice?

AFAICR the original orings were nitrile and so I’d avoid replacing with genuine parts for this application as the same problem will just reoccur. Unless Honda have changed the material at a later date to allow for this.

Yes Viton is safe for all modern fuels.  Most modern automobiles use nitrile for their hoses and o-rings in the fuel systems.

[Oddjob]

Actually not 100% true that, not safe for bio diesel for instance. Not a factor for us to concern ourselves with in this case. However, whilst nitrile is ok with fuel up to 10% ethanol as that figure increases so corresponding does its ability to cope with ethanol decrease. There are also warnings online about constant immersion in fuel with ethanol in it, which I would say around a jet upside down in a float bowl would qualify it as.

We are already at e10 in the UK and I would suspect this is the thin edge of the wedge and higher E numbers are already being planned.

My point being, why risk it, just fit Viton ones and have some peace of mind. The difference in price is negligible really, do it once and do it right is a good saying.

[ozzybud]

Oddjob.  Is it your job on this forum to disagree with just about every post that i make on here?

I post from my experience and what works for me. I ask you to do the same. Isn't this why you got booted from the forum?

Friends don't let friends put ethanol fuel into their classic cars .motorcycles and lawn equipment. It gathers water and ruins everything. In your daily driver its fine. But periodic use machines is a Hard No for me.

If you have to use E10 fuel I get it.  We can get ethanol free gas in the states.

[ozzybud]

This quote is from Hondaman on the us Forums. And i trust everything he  says!



"If they were NOT Viton O-rings, they would probably work well. Since they are, though, the 3.5mm dimension might be tighter than the ID of the wasp-waist groove where it sits. With Viton you mustn't make it stretch more than about 5% of its ID or over time it will break: this is partly why Buna 70 remains king in the ethanol-laced fuel world, because it expands when ethanol hits it and shrinks again when it dries out. This prevents them from self-destructing."

[exvalvesetdabbler]

It has been my experience also to see viton o rings not liking to be stretched.  A lot of science equipment that I worked with used o rings to secure membranes onto sensors that required a bit of stretch to get them on.  Nitrile was always ok. The black viton o rings would break or once stretched  would  not recover. On some kit  large nitrile o rings were used as drive belts.

HNBR are ok if you can get them. TFEP | Aflas O-Rings are also used in the auto industry.
Regards
Dave

[McCabe-Thiele (Ted)]

Oddjob.  Is it your job on this forum to disagree with just about every post that i make on here?

I post from my experience and what works for me. I ask you to do the same. Isn't this why you got booted from the forum?

Friends don't let friends put ethanol fuel into their classic cars .motorcycles and lawn equipment. It gathers water and ruins everything. In your daily driver its fine. But periodic use machines is a Hard No for me.

If you have to use E10 fuel I get it.  We can get ethanol free gas in the states.

In defence of Ken do you expect us to know you have Ethanol free Petrol in the US?

Why not stick to the US forum rather than make inappropriate comments here stirring up old wounds.

This forum gives advice, you can choose to ignore it without winging.

[SteveD CB500K0]

Stop bickering you lot.


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[Bryanj]

All i can say is i have had mamy kits frpm Julir for 500  600 550 anf they work fine.

It was me who found a VERY old parts book with individual O ring numbers and sizes, i used to sell oil pump kits and worked out the size for cover O ringbut my supplier changed minimum order to 1,000 of any one size so i gave up, gratefull to Julie for keeping the supply going

[Oddjob]

Surely the point Mark Paris is making is more to do with fitting smaller than specified orings in the first place. A 4.11 ring wouldn’t need to be stretched out of spec.

And no I don’t post to contradict you, I just don’t happen to agree with you in this instance, plus as Ted says, we don’t have ethanol free fuel readily available in the UK, and as we are on a UK forum and those fuels are currently available are becoming harder and harder to find, I feel my advice to fit viton rings much more suitable for UK riders. If you disagree that’s fine, we are all entitled to our opinion.

[McCabe-Thiele (Ted)]

Stop bickering you lot.


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When I wrongly  quoted the O ring part number  being available at Fowlers Ash pointed out my error with humour.

My rant is over, Steve Ill keep stum.

[ozzybud]

I was only trying to be helpful.
The original poster was asking for the correct size and I posted the picture of the bag with the correct size
Peace ✌️

[scifi]

The only place in the UK for Ethanol Free is at airfields.  My local garage only sells E10, and does not even have E5 these days.

Thank God the Budget kept our 40 year tax and MoT exemptions.  I would hate to pay for all that on my fleet of vintage bikes.

[Seabeowner]

Just reading this whole thread. The Fowlers listing is in 1/10s of a mm! And is 4.9 x 2.5m so still far too big:
https://www.ebay.co.uk/p/1815886647

I have found that nitrile O rings on the main jets actually just expand a bit with E5 and seal better. Have seen no deterioration apart from that over the years.
Just to add to the confusion I thought the Honda size was 3.5 X 1.2mm but never found them listed as a separate part for the 500 as they came with the main jet:
https://www.davidsilverspares.co.uk/CB550K0-1974-USA/part_5119

But I have used 3.5 x 1.2mm, 4.0 x 1.2mm (which I think HM recommended some time ago)

I use E5 80% of the time and have have thrown E10 is sometimes when topping up and found it OK. If storing for a period only E5.
But don't break up the happy home. I find it's always best to put your argument once and disagree, but don't prolong it and hijack the thread....which I have done.

[exvalvesetdabbler]

These are easy to find. And what I have settled on.  Thanks
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[Oddjob]

Just reading this whole thread. The Fowlers listing is in 1/10s of a mm! And is 4.9 x 2.5m so still far too big:
https://www.ebay.co.uk/p/1815886647

I have found that nitrile O rings on the main jets actually just expand a bit with E5 and seal better. Have seen no deterioration apart from that over the years.
Just to add to the confusion I thought the Honda size was 3.5 X 1.2mm but never found them listed as a separate part for the 500 as they came with the main jet:
https://www.davidsilverspares.co.uk/CB550K0-1974-USA/part_5119

But I have used 3.5 x 1.2mm, 4.0 x 1.2mm (which I think HM recommended some time ago)

I use E5 80% of the time and have have thrown E10 is sometimes when topping up and found it OK. If storing for a period only E5.
But don't break up the happy home. I find it's always best to put your argument once and disagree, but don't prolong it and hijack the thread....which I have done.

If you look at a very early parts book for the 500k0 you’ll find them not only listed as a separate part but with a size shown. Bryan allowed Ash to copy his original parts book and it’s available to download on the site if you want to look and confirm what I’ve said. It’s why my first post on this thread was to advise what Honda says is the size. You’d expect them to get it right. Knowing how Honda think and do things it doesn’t surprise me they stopped listing them as available separately as it’s more profitable to get you to buy a main jet as well just to get the oring.


I do seem to recall Julie saying they were testing nitrile orings in ethanol petrol by leaving them in a jar and seeing how they performed and the answer was not that well iirc. But I’ll leave her to confirm if that’s true or not.

Those should be ok size wise dabbler. To get the exact size from Polymax means ordering 500 a time, not a great idea if you just want 4.