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OEM 1974 T100R carburetor beveled spray tube
#803154 03/28/20 1:47 pm
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Lucas57 Offline OP
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I am in the market for a new Primer AMAL Carburetor for a 1974 T100R Triumph Daytona. The OEM for this model/yearmodel is dual 626 AMAL Concentric carburetors. I have been in touch with AMAL UK (see attached screen shot). From the information I believe that this was a unique year and model in terms of carburetor configuration. According to AMAL support staff the OEM AMAL 626 carburetors for this model/year had a beveled spray tube. From all the info I can find including AMAL technical publication the beveled spray tube is exclusively for a 2 stroke and the Trident. The square, flat spray tube was the common configuration for a 4 stroke. I also understand that all I have also researched published info by John Healy who I understand knows AMAL carburetors and again there is no mention to support what I am hearing from AMAL’s technical staff. I find this lack of supporting info confusing
[img]https://www.amazon.com/photos/shared/vP9Xe97WQVyZ8i3VYupgpQ.m819iZ5WEpTFwvphg5pJvh

Last edited by Lucas57; 03/28/20 2:09 pm.
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Re: OEM 1974 T100R carburetor beveled spray tube
Lucas57 #803158 03/28/20 2:39 pm
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I’d try to tune it with a flat topped spray tube first.

The bevelled tube may have been a bodge to meet emissions requirements.


Amateur Loctite enthusiast.
Re: OEM 1974 T100R carburetor beveled spray tube
triton thrasher #803159 03/28/20 3:04 pm
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Lucas57 Offline OP
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Thanks for your reply. I wish is was just a simple matter of switching spray tubes. The spray tube is pressed into the upper body. The only way to try out different spray tube designs would be to buy and test 2 complete carburetors

Re: OEM 1974 T100R carburetor beveled spray tube
Lucas57 #803161 03/28/20 3:13 pm
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Quote
No, they can be replaced.
The only way to try out different spray tube designs would be to buy and test 2 complete carburetors[/quote]

No, they can be replaced.

Re: OEM 1974 T100R carburetor beveled spray tube
John Healy #803163 03/28/20 3:44 pm
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Lucas57 Offline OP
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I am trying to find out 2 things. 1. what was Triumph trying to accomplish with this change To the 2 stroke spray tube for the 1974 T100R
2. For general use which would be the best choice of the OEM 2 cycle type spray tube type or the more common flat top spray tube type carburetor

Re: OEM 1974 T100R carburetor beveled spray tube
Lucas57 #803165 03/28/20 3:47 pm
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The Trident bevelled spray tube was different from the two-stroke bevelled spray tube.


Amateur Loctite enthusiast.
Re: OEM 1974 T100R carburetor beveled spray tube
Lucas57 #803185 03/28/20 6:42 pm
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The period after the workers took over the factory in 1973 disrupted the flow of technical information we normally would receive from the factory and the US distributors. Also Norton, in the form of NVT, was running the distribution of Triumph and Norton motorcycles in the UK and around the world. Normally a change like that would have been documented in an addendum to the parts books and technical service sheets. Also the technical staff in the US was all new, or Norton. All of the people at Triumph that new anything had been let go when Peter Thornton was made director of the US company.

My 1974 parts book has been updated to the carburetors used on earlier T100R models. Where we got that information is unknown some 40 plus years later. What actually came on the 1974 as far as a spray tube is purely anecdotal at this point. Before this post I had no information that indicated a change was made, AND if it was specified whether it was ever acted on in production.

As we know from all of the Addendum sheets that came with the parts book the book, or other information from suppliers, is what was listed in the parts book was NOT always what was put into production. Triumph produced three different basic parts books: domestic, general export and USA versions. All three had different specifications to suit the market the bikes were made for. Then the distributor published addendum sheets that reflected the specifications for how in the end it was actually assembled.

On the whole, parts books a better used for their pictures which are often more accurate than the parts listed.

Further to this the Daytona has had unique problems with vacuum signals. This is especially true when the vacuum in the intake manifold is drawn on the over-run (decelerating). It draws all of the fuel out of the fuel passage from the float bowl leaving nothing for the engine to run on when the idle carburetor fuel delivery is called on for the engine to run at low rpm. The bike will spit back through the carb (lean) and engine will stall.

We supplied Dick Harris (old timer that puts on thousands of miles on a couple of 1970 Bonnevilles and a T100R, sets of pre-production Premiers. The results with the Bonneville's was very encouraging!!! The Daytona was another thing all together. We made quite a few changes to the jetting, but the bike fell back to the original problem that the Daytona had before they moved the pilot jet (main jet for idle carburetor) closer to the outlet into the venturi. It wasn't as bad, but still annoying.

Now you might have have some information, while still anecdotal, whether the 74 came with a slant spray tube. Look at your carburetor.
We might all learn something!
Don't blame Burlen they are only using information passed down from AMAL. Anyone who has worked in the British parts business has come to learn that what was going to be used is not what was actually used.
John

Re: OEM 1974 T100R carburetor beveled spray tube
Lucas57 #803292 03/29/20 5:07 pm
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I purchased this bike in the spring of 1977 from the original owner. It as low mileage and pretty much stock. I have no reason to believe that the carburetors were anything but the stock original. They are marked 626 R64 and R65. They have the 3.5 air slide, a 150 main jet a .106 needle jet, a 2 ring needle in the top position and a spray tube the same angle as the the one normally reserved for 2 stroke application. This all is consistent with AMAL’s description of the correct carburetor for this year model. In light of all this I would think it is safe to think that This year model did have a unique approach to the bikes carburetors despite the lack of support in the history. Or other.

For me the question remains. Why did they do it. Was it to fix a performance flaw and if so did it work? Was it a screw up in the assembly process that when unnoticed or overlooked. Or was it done like suggest above to satisfy emissions regulations which were alive and well at the time.

I have not mentioned yet that I did buy the PACK 144 Premier AMAL carburetor. It arrive a few days back. This was good because shortly after receiving it I received an email from AMAL saying there production shipping has temporarily shut down. Also when I purchased these carburetors they had only 2 sets in stock. Now they have only one and one and it might be a while.

Re: OEM 1974 T100R carburetor beveled spray tube
Lucas57 #803294 03/29/20 5:28 pm
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As John has mentioned above the situation at Meriden in 73/74 was a state of complete turmoil.
Anything could happen and very often did!
If you think the carb configuration is original and it runs good like that then leave it as it is.
If it doesn't run well then change the carb spec to a spec where the bike does run well.
A 72 spec might be a good start point.
HTH


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