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Stromberg carbs

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countennis

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I have installed in my TR250 two Stromberg carbs that were previously overhauled by Gary Martin. I have balanced the carbs.
I discovered that the fuel mixture was very lean in both carbs.
I have the correct jet adjusting tool, but the diaphragm tube on both carbs don' have the notch for the jet tool to lock into.
Also, when turning the hex tool it always just turns around and around. The hex never engages the jet. Any ideas?

Thanks,
Jack
 
Hi jack

I believe that the early as carbs have fixed non adjustable needles. I am sure that the carb experts will jump in here.

Cheers
M pied Lourd
 
Not sure what would be correct for a TR250, but on the TR4 which has fixed needles the mixture is adjusted by moving the jet from the bottom. If you have a large adjustment screw on the very bottom of the carbs you likely have that setup.
 
In case you are unsure which carb you have... this is what the early Strombergs looked like:

TRI-014.gif


They are adjusted by turning that 'nut' (item 26) -- has a slot so they can be turned using a quarter (or I prefer a 2 shilling coin).

Carbs in situ...

TR4Carbs.jpg
 
As Pied suggested, the TR250 and early TR6 carbs had no adjustment for mixture, beyond a very small air bleed (aka "idle trim") screw.

There are several ways to gimmick them, including sanding down the needle and moving the jet a bit lower in the housing. But the best solution IMO is to source the pistons (or complete carbs) from a later car, with the factory adjustment inside the dashpot.

I believe the Buckeye site still has the article on how to modify the early pistons, but it looks like a lot of work and you still need to source several parts from a later carb.

OTOH, they shouldn't be "very lean" unless something is wrong. I'd be looking for something outside the carbs, like maybe a leaking brake booster or weak ignition system.
 
Thanks!

I don't think it is an ignition problem as I have a Petronix
setup.
Will check the vacuum situation. Don't think it is a booster leak, but I do have the rest of the vacuum ports blocked so I will check all of those.
 
Hi Jack
While you are adjusting the mixture on the bottom of the carbs, which raises or lowers (which is what you need in order to get a richer mixture) the jet.


Here is something to think about from the humor section: :jester:


As he stared at her ample bosom, he daydreamed of the dual Stromberg carburetors in his vintage Triumph Spitfire, highly functional yet pleasingly formed, perched prominently on top of the intake manifold, aching for experienced hands, the small knurled caps of the oil dampeners begging to be inspected and adjusted as described in chapter seven of the shop manual.

--Dan McKay, Fargo, North Dakota (2005 Winner)
 
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