Posted By : Chris Taylor,
14-Jul-2007, 07:22pm
If you use a thinner oil, you will not get quite so much mixture enrichment when you open the throttle. Response will be, if anything,
worse, but might save a teaspoon of petrol a week.
But the choice of needle, and air valve spring etc, as well as the type of oil to use in the dashpot were worked out as part of a whole by
Triumph during the development of the cars to ensure they ran as well as possible given the basic design and state of tune off the
production line. SO WHY DO SOMETHING DIFFERENT?
Other makers may have come up with slightly different set-ups (eg lighter dashpot oil) ON THEIR ENGINES, but why should that invalidate
what Triumph determined was the optimum set-up for a standard car?
There are some in the Triumph world these days who DO know as much or more than Triumph's engineers, but there are not many such
individuals. For the rest of us mere mortals, I can only reiterate that Triumph DID know what they were doing and we should stick to
standard spec for standard vehicles. Unless you go in for comprehensive modifications, which should encompass ALL the interrelated issues
of gas flow, ignition, carb settings, much so-called tuning is unproductive fiddling and a waste of time! By all means take advantage of
superior more modern materials (eg brake pads or silicon HT leads) and components like spark plugs, but don't be fooled into thinking there
is some magic tweak that Triumph's millions failed to find, just 'cos some mate down the pub recommended it. If in doubt, just look in the
manual or the original owner's handbook! (The Club shop sells them). Or speak to some of the REAL experts in the trade, and they tend to be
the guys that don't make extravagant claims. And because they do know what they are doing, they tend not to need to advertise much, which
makes finding them more difficult!!!
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Posted By : Adrian Dean,
14-Jul-2007, 07:52pm
20w/50 Engine oil it is then.
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Posted By : Peter & Mick
Lewis, 14-Jul-2007, 08:28pm
if you took the air piston out to drain it have you put it back the right way round,, there is a lug on the diaphragm that locates
into a relief in the body, also the same device is under the diaphragm fixing ring this controlls the position of the vacuum holes
on the bottom of the air piston just a thought ..... peter
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Posted By : Chris
Taylor, 15-Jul-2007, 06:40pm
Engine is unlikely to run at all if the air valve is in the wrong way round. The "vacuum transfer holes," if you can call them
that, will have no vacuum as that is generated downstream of the jet bridge.
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Posted By : Jon Morton,
14-Jul-2007, 10:51pm
Wow angry answer Chris, please try not to be to aggressive as it does scare some people off sharing their thoughts on the message
board
Yes the triumph designers knew what they were doing and yes if the oil is too light it will make the mixture to lean.
I think in principle we seem to agree. However engine oil can be too viscous in some climates, but not a problem in the UK (this is
read worldwide.)
As to the quote "There are some in the Triumph world these days who DO know as much or more than Triumph's engineers, but there are not
many such individuals. For the rest of us mere mortals,..." I would like to quote R. J. Mitchell designer of the Supermarine
Spitfire,"anybody ever tells you anything about an aeroplane which is so bloody complicated you can't understand it, take it from me:
it's all balls".
There were/are after market modifications which were popular while our cars were still being manufactured, these were/are seen as
improvements by a great many people, even though for one reason or another triumph didn't implement them (quite often cost).
I for one have a phoenix tubular exhaust and twin pipes, alloy rad, electric fan and ported and polished head, covered by a fibreglass
bonnet. I'm setting up a pair of webers now and am half way through making a set of the custom bike carb manifolds. No I don't and have
never professed to be an expert and the changes I've made would not suit everyone, most certainly not a mass produced Triumph. But I
think its a shame to put people off trying things out with ridiculous scare stories.
I would really like to reiterate as I have done many times on the forum, don't be scared to have a go with these cars. One of the great
joys of owning one is to get you hands dirty.
No offence meant Chris
Jon
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Posted By : Ed Weller,
14-Jul-2007, 11:00pm
I use 3 in 1 and never had any problems - engine pulls and idles extremely well!
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Posted By : Adrian
Dean, 14-Jul-2007, 11:42pm
Actually I have a 70's "AA Book of the Car" and it says to use single grade oil (20 visco thingies) in SU and Zenith dashpots
so that you get even response across all temperatures. But how would a dashpot tube get so hot as to change the viscosity of
the oil inside it? GT6 workshop manual says Zenith "Lube Pack" oil OR engine oil, I assume the lube pack oil is a monograde oil
not to be confused with Lurpak which is in fact a dairy product from Denmark.
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Posted By : Peter &
Mick Lewis, 16-Jul-2007, 08:30pm
well done Jon experience is for sharing not shouting, and Adrians right but use the lurpak spread it thick loads of
cheese
I cant believe nowone's come across ,,or fitted diaphragms the wrong way it was common in the 70s
I ran a petrol and diesel emmission facility for some years in the 70/80s carbs were mainly fixed jet but with the dyno on
song you could plot an ant farting at ten feet get the gas in a bag and tell if it was watney's red barrel or brewery tap
ale,,,,have fun Peter
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Posted By : Adrian
Dean, 27-Jul-2007, 03:46pm
So, been a bit busy and it's been rather wet since I last posted about this so haven't done much, anyway, changed the
oil in dashpots back to engine oil and same problem persists though not as bad as before, but now the tickover has a
mind of its own. I adjust it to 800 or so then when I blip the throttle it goes down to 500 and wants to stall then
blip it a few times quite hard and it settles at 1200 or so. Took it for a blast to clear the passages, so to speak,
and then it seemed fine but after reversing back up to the garage the tickover went back to 500-400 and she tried to
stop again. Any ideas?
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Posted By : Chris Taylor, 27-Jul-2007, 05:34pm
The most usual cause of irregular idle speed is worn throttle spindles allowing air to leak in bypassing the
throttle plate. This affects both the volume of mixture entering the engine and the air/fuel strength of that
mixture. Try wiggling the ends of the throttle spindles and see if there is visible play there.
It is just possible that taking out the air valves they have not gone back in exactly the same position. Make sure
that the air valves can be lifted smoothly throughout the complete travel and that they drop with a click onto the
bridge whenever you release them, whether from fully raised or a couple of millimetres. If there is no clear click,
you may have to recentralise the jet as described in the workshop manual.
If the air valves are slightly sticky in their movement, you could try loosening the 4 securing screws and
tightening gently and evenly, possibly across diagonals, and not too tight (the diaphragm will ensure an air tight
seal) to ensure there is no distortion through overtight screws.
If you've got the carbs in bits, it's worth checking that the metering needles are fully tight in the air valves,
and that there is no relative movement between the steel centre of the valve (the bit the needle fits into) and the
rest of the alloy valve (the bit the diaphragm is fastened to).
Mucky float chambers and/or poor floatchamber valves may cause erratic idle by not maintaining a consistent fuel
level, but I would have expected that to manifest itself in other ways (tendency to flood, leak, run rough at other
engine speeds etc).
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Posted By : Adrian Dean, 27-Jul-2007, 09:15pm
Thank you Chris!
Sometimes it helps to have someone point out the blitheringly obvious to you before you go off one one about
microscopic bits of fluff blocking this or that orifice or slightly the wrong viscosity of oil etc etc.
Took off the socks and noticed that the front air valve was not returning to the bottom of where it should be
and was sticking sometimes. On loosening the dashpot cover screws I heard a "tick" and the valve hit the
bridge! I undid the screws and tightly held down the cover until the piston dropped easily and nipped up the
screws gradually, problem solved. Screws too tight distorting or causing cover not to seat properly and rubbing
against upper part of the tube of the air valve that you fill with engine oil!
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Posted By : Chris Taylor, 27-Jul-2007, 11:51pm
I hope that solves your problem. If you find it keeps recurring, it MIGHT be the case that you fitted the
wrong top to the wrong carb. While the parts should be interchangeable, after working together for nearly
40 years, the original parts will have worn slightly to match each other and may not take so kindly to
being swapped over.