Honda-SOHC
Other Stuff => Misc / Open => Topic started by: Oddjob on January 19, 2023, 10:25:32 PM
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Just taken apart my petrol cap that came with the new tank today. All the O-rings have hardened and the 4 way rubber doughnut behind the tap itself is also hard as nails.
Got me thinking, has anyone ever worked out the Viton equivalent sizes, the parts book show them as available separately but fails to give the sizes, the most you can get is the one between the cap and the tank described as 23mm but no section width. What with DS wanting £5.54 for one and £6.01 for the other (you can bet these are old parts so most likely nitrile and not Viton and due to the exposure to modern fuels we should be looking at Viton ones as a replacement) these aren't exactly cheap but most likely the Viton equivalent will be miles cheaper. The 4 way doughnut thing I'll have to source as genuine. Float bowl is rounded off so a new one of those is needed as well.
I can guess the sizes but the ones I've taken off are really flat so getting a section size could prove tricky.
So anyone already done this?
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I've used 23 x 2mm c/s for the one between petcock and tank and 28 x 2.5 (which may be a bit big but squeezed it in) for the bowl. If you haven't moved since 2017 (have an address) I'll send you them to try and maybe adjust if you feel necessary.
Presume this is about tap and not cap.
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I did measure the one between tap and tank and I also thought it was around 2mm, the one under the bowl I made out to be 30mm though, that was by measuring the old one across it's widest point. Saying that I'm wondering if the sizes relate to the internal diameter rather than the external, as 28mm plus 2.5 each side would make it 33mm? I have a stack of orings lying around, I may try and see if I have any 26mm x 2mm ones, the bowl oring was actually not in bad condition and looked to be 2mm rather than 2.5mm.
I'm also wondering if the doughnut shaped one can be home made rather than paying over £6 for what is bound to be Nitrile and thus not resistant to the Ethanol in fuels these days. I measured the thickness last night and it looks to be around 3mm, I have some really good hole cutters so I just see if I can find a sheet of 3mm Viton and punch out my own, may be the way to go.
Yes, about the tap not the cap, I bought a few spare rubber gaskets for the cap some years ago, never had to use one but the cap gasket is very perished on this one.
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Seems you do measure the ID of then ring, then add the cross section of the rubber. So 26mm + 2mm + 2mm is the 30mm I measured.
Found some viton 3mm sheet on ebay so I'll give that a go as well.
Cheap enough to buy 10 of each rings but appreciate the offer.
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Been doing a little work on the petrol tap from the second hand tank. Just mucking about really, tidying the tap up, what started as just a little tidy up ended up being a bit OTT to be honest, let me be clear this is NOT polished, I don't intend to polish it, I may polish the lever if I feel like it. This has just been dismantled and sanded using the little abrasive discs from Amazon, anyone can do this. What started as a pretty rough casting has slowly been sanded, started with 80 grade disc, just to get rid of most of the casting marks, then progressively down the grades, 120, 240, 400, 800 and finally finished with 1000 grit disc, light green to be exact. At each stage it got shinier and shinier, however the last 2 grade discs were contaminated with buffing soap and this transferred itself onto the tap and in the end I needed to clean the surface with some Brasso felt wool, which to be honest dulled the surface down a little.
Anyone can do the same, all they'll need is a set of discs and a Dremel. I have replaced the 2 small screws holding the lever plate in place with some stainless ones, you could of course replate the originals instead or even just use the existing ones but they will rust.
(https://i.postimg.cc/nhkBpTyg/IMG-3011.jpg) (https://postimg.cc/tssYzdCN)
(https://i.postimg.cc/V6SC9wJP/IMG-3012.jpg) (https://postimg.cc/TL61GZjt)
It's not really that visible but I feel it looks better than that dirty grey look is normally has.
The only worrying thing is that I reinstalled the doughnut washer behind the lever, mine for some reason seems to be made of cork not rubber, it doesn't seem to be sealing as I can still blow down the brass tube with the lever in all positions, saying that the cork doughnut isn't in the best of conditions so that may be the reason.
When I get round to assembling it back together I intend to replate the plate with the markings on so it doesn't rust.
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oh crap now i need to polish something else!
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Thats ace Ken, well done mate.
I'll send you some new finger tips up in the post, that lot look knackered after making such a great job of that. ;)
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TBH Roo the garage was so cold today that my fingers were numb, the dirt is residue of the buffing soap. The tap was easy to do, just took me a few hours. Not 100% sure if the 550 tap comes apart but if it does it should also be an easy job to do.
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The King of Bling has been at it again. Nice job on the tap Ken! Only a few hours! 🥵🥵 I’ve gone for shabby chic on mine.😉
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That looks great Ken,
When you say 'blow down the brass tube'. Do you mean the long one? Air will always have an easy passage down that as it comes out of the reserve drilling lower down (also known as the R's hole :))
Roo, I'll buy some of those finger ends - I can stick them on rubber gloves and go 'a burglarin'. Saw it in an old movie!
Ian
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Long time shop in Kings Road
[attachimg=1]
Often with tourist having their picture taken outside when I've past there.
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Long time shop in Kings Road
(Attachment Link)
Often with tourist having their picture taken outside when I've past there.
🤣🤣🤣
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Ken, never seen a cork tap seat, suggests a home brew idea. I have turned the Honda rubber ones over before now as the sealing holes have a raised lip that wears away.
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Noticed that Bryan, I'm going to buy a genuine and see if that seals up the brass tube. I seem to recall that when the tap is shut it's supposed to blow anything coming down that tube as otherwise the tap is in effect constantly open. We'll see when the new seal arrives. I repaired the bowl as well BTW, it was totally rounded off by some ham-fisted amateur so I filed flat spots on it until it looked like a nut again, you can see the corners aren't as crisp as they should be. I'll buy a new bowl as well and keep that for a reserve.
I'll also measure the new doughnut seal and see how thick it is and have a look at making some replicas in Viton rubber. The back of the lever is smooth so a little silicon oil or grease on there to help it slide should stop it wearing as fast as well. If it seals as well as the original one I'll make a few and sell them on. £7 for a little rubber that TBH is no longer suitable for modern fuels is a little expensive.
Yes, Ian I did mean the long one, as above, pretty sure it should seal when the taps closed but it could be leaking past the doughnut seal, saying that, I've just remembered I have a new tap somewhere so I'll test that and see. Got the money Ian, lever in post later today hopefully or definitely by tomorrow at the latest.
King of bling, I like that. I've been called much worse over the years. Must admit to liking stuff to be shiny rather than dull. Nothing against Matt paint for instance, it can be very effective for contrast in places.
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I was correct, when the tap is either shut or on reserve you cannot blow down the long tube. Just checked with my new tap.
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Just ordered a new bowl and doughnut seal from DS. Also after a re-measure with a digital vernier I concluded that the bowl O-Ring is more 31mm than 30mm, the thickness was around 2.67mm and concluding that it must have been squashed in use I think the initial thickness was more like 3mm, so I ordered some Viton O-Rings at 25 x 3mm and just in case some 26 x 2.5mm, I'll see which suit better when they arrive. The tap to tank O-Ring looks to be 2mm but again it's almost flat, so to cover all the bases I ordered some 23mm x 2mm and some 23mm x 2.5mm and again I'll see which suit better.
I'll wait for the new doughnut to arrive to see what thickness of Viton sheet I should order to make some new ones.
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Ah yes Ken,
The long brass tube goes right down to the body of the tap with no side hole and there's a separate hole for reserve. Otherwise you would have no reserve! Must go back to skool!
Ian
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As I say I've been using 23 x 2mm c/s and 28 x 2.5 for about 4-5 years on a couple of bikes and I think they may be nitrile. Know that as the bowl one expanded a bit and had to stuff back in but actually seals just fine.
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It's odd, don't you think, that people and recommending we use Viton O-Rings because of the Ethanol in todays modern fuel. We are advised to replace all the O-Rings in the carbs due to the exposure to the new fuel YET no one says anything about the petrol tap O-Rings. Yet if anything the tap is exposed to more fuel than the carbs, we drain the float bowls in Winter be we don't drain the tank so the tap is constantly exposed to the Ethanol. We also say nothing about the inlet manifold O-Rings which are exposed as well, not as much as the carb and taps admittedly but they act as a seal against the outside environment so they must be exposed to some of the petrol vapour but we don't say anything about replacing them.
At 28 x 2.5mm I'd say the ring was 2mm oversize, which may explain why it needs to be stuffed back in. I'll see when the new rings arrived. I think the 23 x 2mm was pretty much spot on. I'll see though if 2.5mm would be better or worse.
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Inlet manifold o'ring is a air seal and not a fuel seal and it does not come in contact with fuel ;)
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Got to disagree Graham, it’s both, stops air getting in and thus stops petrol vapour getting out. There must be some exposure to the petrol or even if the oring fails it wouldn’t be able to access the air inlet tract. The main difference is that the vacuum in the inlet tract mainly encourages ingress of air rather than the other way round but something like a backfire through the carb would allow exposure the other way as well.
It can’t hurt to eliminate the chance of ethanol exposure to the oring by replacement with viton rather than nitrile. Same to some extent could be said about internal engine orings, we’ve all smelt petrol in engine oil for example, is that harming the nitrile rings in the engine?
Not arguing this is the case just seeing what the general thoughts on this theory are.
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We use Viton O rings on all engine oil ways and of course the oil pump. The only Nitrile we use are on the tappet caps as its not an oilway and Viton is too hard for there anyway. Having had 2 jars of Ethanol petrol on the bench for 3 years now, one with Viton and the other with Nitrile submerged, yes, the Nitrile has disintegrated totally, ie, gone all stretched and sort of melted, the Viton hasn't been affected. But, the O rings suspended in the jars on lengths of wire, suspended above the fuel, therefore only in the fumes, neither have disintegrated........so far 😊😊😊😊
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Interesting Julie. So if that is correct and I have no reason to doubt it, then only by being submerged or constantly exposed to fuel causes the Nitrile rings to deteriorate, exposure to vapours and such either doesn't or takes far far longer to become apparent.
I wonder as the levels of Ethanol increase whether the deterioration increases as well. A couple of years ago it was 5% now IIRC it's already at 10%. Saying that they have E85 fuel in the US and certain European countries, that's 85% Ethanol and only 15% petrol. You can almost see the orings melting can't you? ;D ;D
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I'm sure that when Ethanol was introduced into the petrol the recommendation was to replace o-rings and rubber seals in the fuel system as a whole. That would include the fuel tap.
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Got to say that nowhere to my knowledge has anyone said anything about replacing any orings except for this forum. When I mention it to other bikers for instance they are totally unaware of it, as I’m sure are 99% of car drivers.
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Surely if and when the nitrile rubber starts to swell, disintegrate the surface area will increase slightly due to pits and holes and larger overall size?
This would suggest that when they start to go the process would only accelerate as more of it would be exposed ?
RE. If a ring has gone somewhere in /on the bike and it’s an OE piece, it could be assumed that the majority of the other seals in the machine that are subjected to similar conditions will be going or gone also meaning that as soon as you see one, it’s time to get all the others changed also?
Sent from my iPhone using Tapatalk
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As it's been said Roo, it's really only O-Rings and possibly seals (unsure what they are made of TBH and may already be immune) that are essentially submerged in the Ethanol inside modern fuels, carbs and taps for instance. I'd advise doing the internal engine O-Rings as well if possible to eliminate the potential of a failure in the future. That is of course if Viton rings are available in the sizes required. TBH I wouldn't advise pulling an engine apart to replace the O-Rings as the amount of Ethanol they could be exposed to doesn't make it worthwhile and the amount of time it would take for them to become a problem means it's just not worth it. However if you are already replacing O-Rings in the engine then I'd say might as well fit Viton ones instead, if possible of course.
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Got to say that nowhere to my knowledge has anyone said anything about replacing any orings except for this forum. When I mention it to other bikers for instance they are totally unaware of it, as I’m sure are 99% of car drivers.
First post in this topic.
http://www.sohc.co.uk/index.php/topic,26449.0.html
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That post was a comment and post from a friend of mine after I’d brought the subject up on another forum, he was trying to clarify all the mistakes and myths regarding Ethanol. The only reason he did that post was in answer to my comments in relation to the problems ethanol could cause, not in our bikes though as they are all post 2000 models but in any other bikes the members may also own. Members were surprised that the government hadn’t bothered to warn anyone about what introducing this into our petrol could cause.
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To do that would mean they were not all lying
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O-Rings have arrived. All the sizes fit. I'm leaning toward fitting 23 x 2.5mm between the tap and tank as it seems to protrude more from the body of the tap, the 2mm one protrudes but I'm thinking it's better to have a little more compression available rather than a little less.
The bowl one, both look ok TBH, but I'm thinking the 2.5mm might be better as the ID means it's fits the bowl better. I'll test it and see.
The doughnut and new bowl have also arrived. The doughnut is actually 3.5mm thick so I've ordered some 4mm Viton sheet and if I need to I'll sand it a little thinner but I'll test fit it first. All the 4 holes seem to be the same size, which is odd as the pics make them out to have at least one slightly bigger. I'll try a 4mm punch and see if the hole is large enough, if not I may need to order a 5mm one. The diameter is 20mm, in case anyone else is considering doing this. It's also very supple, they don't seem to stay that way for long though. Most of the ones I've felt were hard as rock.
If it all pans out I may sell a set of 2 rings and a new doughnut for £5 inc P&P. Approx £25 for the same in genuine Honda parts and they'll most likely be Nitrile not Viton.