Honda-SOHC

Yes Ash, they fit all the Honda SOHC fours, 350/400/500/550/750, in my poverty stricken youth we would use whatever was the cheapest at the time, and never had any issues. Our local dealer had purchased a job lot of genuine Honda from a bankrupt dealer abroad somewhere, and didn't realise they fitted all the bikes at the time, so I made a cheeky offer of 50p a set for what were listed as 350four points. We convinced him he would never sell them otherwise as that bike was never sold in the U.K. so we got a good deal for 15 full sets, plus 4 extra right hand sets (cyl 2&3) for £17. Wish I hadn't sold them all off now with the cost of genuine these days>

Cheers  spot on reply .. I wonder why Honda had a 300 part and 333 one ? I notice that CMS also sell the 300 part for the 400/4. That's the second set of Gen points I have got off eBay for a tenner .. you just have to scan it all the time and bide your time.

Ash

Liking the choice of paint colour there !! Looks stunning

Ash

Ash... speechless at your tech knowledge. School told me rubber came from trees in Malaysia & signed the topic off there... they woefully let me down!

A big thanks to this thread... my K2 was lately popping at idle... one of those jobs I kept forgetting. Anyways, took a mini socket to all 8 inlet clamps yesterday... every bloody one took a turn or more. Job done... fantastic.

Slight topic drift Ash... but you're the man... storage... better to spray WD40 over the metal parts... or silicon? My bro-in-law telling me WD40 overspray can degrade plastics / rubber, whereas silicone won't. Comments?

Ta,
Simon

I worked for a large company for yonks before I went self-employed about 18 years ago. After many rounds of re-organisation we were wittled down but we had ended up with a really a good technical  team of engineers / technologists. One was a chemist, myself electronics/physics, a rubber technologist, a mellalugist, an engineering plastics  expert and lots of mech. eng. experts. We have all gone our separate ways now but we still draw on each others specific areas of expertise. Sadly the metallugist is very poorly.
 
I will ask the chemist guy about affect of WD40 overspray on polymer parts.

Ash

Emailed this to DS:-

Hello David,

In 2010 I came up with a method of re-softening carb. inlet rubbers for the CB750K0 (no pattern parts were around then). This is a chemical used in the rubber processing industry and not the 'essential oil 'wintergreeen' treatment used by members of the USA SOHC forum.

To this day my sample retains its softness and compliance but has never been fitted to an engine. There was no significant swelling due to the treatment.

However, I softened a set of K7/F2 750 carb inlet ones for an SOHC.co.uk forum member and he is reporting inlet leaks so I am not sure on the 'Compression Set' properties on the treated rubber (the CB750K7/F2 ones are really expensive and as far as I know not reproduced as aftermarket parts).

However a few forum members have purchased aftermarket inlet rubbers and report similar leaks shortly after fitting, which worries us a little about fitting aftermarket parts. As I understand these aftermarket parts were sourced from the USA. I know you now sell aftermarket inlet rubbers for some models (including the CB750K0). Do you have any specification details of the rubber used in these please from your supplier ? I had a set of original '69 inlet rubbers analysed in 2010 and they were made of nitrile rubber. The airbox 'rubbers' were a form of polyurethane, borne out by the fact that, in the softening solution they actually hardened more ! If you don't have the technical spec. of the rubber used on the aftermarket parts, I could have these analysed FOC but I would need samples to try, which may be a destructive test, if I need to get a compression set value measured.

I am not a rubber expert but, as I remember,the Key properties physical & chemical properties are :-

1) Correct Polymer type (including any filler)
2) IRHD Harness
3) Solvent / chemical resistance
4) Compression Set
5) Resistance to ozone cracking (hence black colour)
6) Temperature resistance.
7) Swelling after immersion in petrol.

If a manufacturer cannot supply or understand these properties then I would question their integrity on the reproducing of these critical parts.

I am also interested in the type of rubber used on repro. cam chain tensioner parts. As far as I am aware, nobody reproduces primary chain tensioner polymer components for Honda's.

One member has fitted your pattern inlet rubbers ( I think to a 750K0), so that looks promising. What do you fit to your 400/4 resto's?

Hope to see you at Stafford.

Best regards,

Ash.

You never reported back on your boiler Steve. How did you get on with it ? Or have you frozen your nuts off 

I just found this in my loft.. it was the prototype I made for Stelrad. It also had a microcontroller daughter board that fitted onto the 8 pin header on the RHS that had an LCD with the diagnostics on it.

Anyway the relays, ignition transformer and spark gap, etc , etc  were all standard Ideal issue and apart from demoing it were never used so could yield parts if you want it (free to you of course).

Ash [ Guests cannot view attachments ]

I'd have to agree with you here Pete; the airflow volume would barely be dented by a little porosity?
Poor clamps / new splits .... more believable.

Any mileage Roy, in pressurising the Airbox (Hoover outlet) and then painting a soapy solution abouts the rubbers to look for leaks?

Simon

When I get back to work Simon I will do some testing and plot the air decay after pressurising. There is a rubber property in the 'Industry'  called compression set (CS) . I suspect it may be that the softened nitrile may not have the same CS properties, although the recovery when compressed looked OK to me. Once I have done some tests and consulted the 'oracle' guy, who has worked in the rubber processing industry for almost 40 years, I will post on the US site because they have done loads of softening with essential oils, and we can compare notes.

http://en.wikipedia.org/wiki/Compression_set

One thing I did notice with Roy's parts was that initially there were a few fine threads of rubber came off,  which I assumed was moulding 'flash' but perhaps if the rubbers are removed when cold from the bike, then tearing of the surface layer could occur. I never noticed this on the K0 I softened in 2010.

I will also ask DS if he has any technical info on the pattern ones he sells. I suppose it's guys like Roy who have the biggest problem because the ones for the F2/K7 are mega expensive.

Give me a bit of time to do some experiments Roy. I will clamp one like yours to a K7 carb body, pressurize it and put a pressure Tx in line and plot the pressure decay plus spray the lot will leak detector.

Anyone know what the DS pattern K0 ones are like or the Cruzinimage ones . Or are they the same?

Ash

Ashley Derrick ....‎David Silver Spares
5 hrs ·
Are you at the April Stafford Show? If so will you be offering the 'take orders to show' pickup service you did last year please?
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Ashley Derrick

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David Silver Spares Hi Ash, yes we are and yes we will offer that service. See you there. B.Reg David
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