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Carb data 1978 T140E #121752 08/16/07 1:10 pm
Joined: Aug 2007
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Blapper Offline OP
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Hi all,

I've bought a bike that has had a (un)fair amount of tinkering done by all kinds of spanner monkeys with all the scars to prove it. mad Looking through the bills, I see a 'professional' has spent 8hrs on the carbs. eek In spite of this, it is still running generally rich through out the range, although not too badly synchronised. I thought I would start by checking the standard AMAL Mk2 settings, but my data only shows Mk1 Concentric data.
Does anybody have all jet sizes etc. to hand? Also, how much leeway is there in the standard plug grades? If I change hotter by one or two grades, can I expect damage? I have had advice that low battery voltage causes richness in these ol'Trumps too?
Any tips appreciated. help
Thanks,
Blapper

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Re: Carb data 1978 T140E #121753 08/16/07 2:08 pm
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JubeePrince Offline
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Blap -

Assuming you have stock intake and exhaust:

Main Jet: 200
Needle Jet: .105"
Needle: 2C3 (Position #2)
Throttle Slide: #3

HTH,

Steve


'77 T140J
"Vintage Bike". What's in your garage?

"The paying customer is always right."

Fitting round pegs into square holes since 1961...
Re: Carb data 1978 T140E #121754 08/16/07 2:29 pm
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Paul744 Offline
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...pilot jet = 25.

NB jet holder = 0.878" overall length.

.105 needle jet was stainless steel.
The above was the exact setup for my new '78 T140E.
My '81 T140E had the same except for the needle jet being changed to .106 (brass) & the pilot jet dropped to 20.

Re: Carb data 1978 T140E #121755 08/16/07 3:34 pm
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Blapper Offline OP
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Thanks JubeePrince and Paul744, I hope it helps too. :p

I have just noticed that the left carb has a nozzle sticking out towards the top of the slide housing, but the right carb just has the cast feature that the nozzle is pushed into on the left one. Is this normal, or is it a sign that a carb has been changed at some point perhaps?

Blapper.

Re: Carb data 1978 T140E #121756 08/17/07 3:33 am
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John Cahill Offline
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hi, blapper
I have much the same situation myself right now. I have already replaced the pieces you are asking about (which I still think was a good idea btw). It still runs rich on both sides though. I have ordered new enrichment plungers in the hopes they are leaking from age. Thought you might want to try that, if the needle/jets etc don't do it for you.
regards,
John


1979 1/2 Bonneville T140E
1993 Mazda Miata
2001 Jeep Wrangler
Re: Carb data 1978 T140E #121757 08/17/07 3:53 pm
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John Healy Offline
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The MKII carbs came with two basic set-ups for T140s:
European (non-EPA)
124/026 #15 pilot jet
124/012 #35 choke jet
2928/122 .106 needle jet
2928/030 #3 1/2 slide (leaner than US equivelent)
2622/124 2A1 needle
No air jet fitted

US EPA
124/026 #25 pilot jet
124/026 #50 choke jet
2928/031 .105 (special stainless steel)
2926/060 #3 slide
2928/030 2C3 needle
An air jet was fitted to the central air inlet on US EPA models.

All these sepcs are for bikes with stock air cleaners and mufflers. Any changes require adjustements.

As a practical matter, while one could change a particular part to meet local conditions and riding style, they should not be mixed.

Because the parallel port design used on later models increases combustion turbulence, there is better fuel burn (and cooler combustion temperature) these motors were outfitted with Champion N5 spark plugs. The equivelent "splay" port designs were equipped with Champion N3.

While a lot of people hate these carburettors, I have always liked them. They are best when kitted with the solid brass slides.

While I am not up on UK gasoline, they have been lowering the overall "vapor (vapour)" pressure of our gasoline. This carburetor doesn't handle this very well at all. If you take a bike fitted with MKIIs that shows signs of running rich, and put in some racing fuel (vapor pressure is in a normal range - or as we knew it 20 years ago) and the rich running is often overcome. This, of course, is not an option when using the bike on the street.

The first thing you must do is verify that you have the proper parts in the carburettor.

The non-cross drilled needle jets described by Paul are know in the trade as two stroke and as they have the actual needle jet "port" at the other end of the jet they should not be used with the 2A1 needle.

Now to say the bike is rich begs the question and should be answered with "when?" While you could have a main jet that is so rich as to cause the bike to "8 stroke" it could be so lean on the slide as to cause it to detonate and lead to a seizure.
john who has to go back to work!!!


Re: Carb data 1978 T140E #121758 08/18/07 6:54 pm
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Blapper Offline OP
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Outstanding info folks, thanks :bigt: The breather is still connected to the air box (although it will not be after the winter rebuild) and there is a little oil floating around the area at the moment, but I think that was due to an accidental overfill due to wet sumping. The bike was not run for six years from 2001.
JH: The bike was 're-imported' to England with Baloney cut outward pointing straight through 'silencers' (sounded GRRREAT!). I've since put stock balanced headers and peashooters on - still rich. Definitely on tickover, and seems rich on half throttle can't say anymore at the moment because I haven't any clamps on the pipes at the head or on the balance pipe so I don't want to ride it too much. I can say that there is none of the hesitation you get when going from a weak jet stage to a rich one though.

I will be examining every single part of the bike when I dismantle it, and the carb data supplied will be really helpful.

Has anybody got any ideas about why there is a difference between the two carbs re that pipe?

Also, what about low voltage causing richness?

I've just noticed it still hass 12V coils with BB Mk3 ignition. I'll buy 2x6V for the rebuild.

No need to fiddle with plug grades then? Do I take it that the standard grade is always good?

Thanks for your time guys redwine

Blapper.

Re: Carb data 1978 T140E #121759 08/19/07 1:22 am
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trumpetloon Offline
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You have a long road to travel determining baseline jetting before a non standard spark plug should enter the picture. Get the exhaust finalised, be certain the stock jetting is in each carb, check your timing and air cleaner elements, and plug wires, and carb synch, and never try to jet a Triumph at new moon! wink

As with needle clip positions and "half stepping" needle jets to really balance things out, spark plug brand and heat range generally falls in the category of really fine tuning. Yes, equivalent heat range plugs made by different manufacturers can behave quite differently!

Get a strong baseline tune up in first and work from there. beerchug


1974 TR5T
Re: Carb data 1978 T140E #121760 08/19/07 1:31 am
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trumpetloon Offline
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Oh yes, as you are running a Boyer, a strong battery and charging system are vital to having goods sparks that happen at the correct time. All EI systems need solid supply voltage or they get weird.


1974 TR5T
Re: Carb data 1978 T140E #121761 08/19/07 9:14 am
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Blapper Offline OP
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Excellent trumpetloon, thanks.

You pretty much echoed what I thought, and I agree - I have a long road to travel. Also, petrol has changed a lot since the standard jets were installed.

I hope I don't have to do too much fiddling on a freshly rebuilt possibly tight engine. Still, starting a bit rich is better than weak eh?

Blapper. redwine

Re: Carb data 1978 T140E #121762 08/20/07 2:39 pm
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Paul744 Offline
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Hi John,
just for information, my '78 T140E arrived with the carbs jetted as stated in your settings for EPA & the owners manual stated the same. My 2nd T140 came with an owners manual for '80 showing the same. But the bike was known at Meriden to be for the home market & on my first look inside the carbs I found that the needle jets were .106 & the pilot jets had been changed to 20. Why would they specify different setups for EPA & non-EPA but sell EPA set-up bikes in the UK?

I thought that 2-stroke needle jets have the metering hole at the other end, as you say, & no bleed holes. Yet the pair I was sold look exactly like normal 4-stroke needle jets, but without the cross drilling. I've never had much to do with 2-strokes, could they be a varient of a 2-stroke jet, or just the result of a manufacturing error?
Thanks

Re: Carb data 1978 T140E #121763 08/20/07 2:58 pm
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John Healy Offline
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"Why would they specify different setups for EPA & non-EPA but sell EPA set-up bikes in the UK?"

The answer that makes the most sense to me the Co-operative made them for the US market but we were unable to sell them due to the strong Pound. You could by a Kawasaki Z1 or Equivelent Honda retail for less than $2,000 US and the Triumphs cost the dealer $2,200 and up. They either never left the UK or were re-imported for sale in the UK.



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