The needles are spring biased in a particular direction wearing the needle seat oblong. Pull the lids and pistons and check the fixed needle seats for concentricity. If the needle seats are worn oblong no amount of adjusting will lean the carbs out. The needle seats are available from Joe Curto or Burlen. These seats are pressed in/out of the carb bodies. Note the height (measured from the pedestal) they’re pressed in the body before removal. I had a ‘75 MGB that I commuted 140 miles a day in. The car had a single Zenith installed. Loved that car, hated having to pass California smog every year! I pressed in a new fixed seat every couple of years and always passed my smog test with flying colors. ….. just a thought. Burlen LTD web site also has some tech docs that might be helpful.
A friend of mine just bought a '74 TR6 and it has some carburetor issues that I am going to look into. I'm good at Weber and most US carbs but have never worked on Zenith Strombergs. Thanks for the introduction on tuning.
I had my carbs rebuilt by 'Poolboy' from the 6-Pack forums. I was new to Stroms and attempted to tune them to take care of a bad stumble that developed, and it just got worse. Plus, they looked horrible, lots of corrosion. Just before I sent them off, I realized that the actual problem was me- I had re-gapped the plugs to around .035 IIRC, and they gummed up on the last drive I took. I forgot about my experiment and messed up my carb tuning! New plugs conservativly gapped solved the problem, but I still wanted fresh carbs and sent them to Poolboy anyway LOL. Carbs take a lot of practice...
That’s a pretty tired engine, so those are probably pretty tired needles and valves. Specs are online. In defence of Zenith Stromberg carbs, I’ve got twin SUs 1.5, twin Strombies 1.5 and twin Strombies 1.25 for my 1500. My first choice is the Strombies for reliability and stability. Someday I’ll get around to doing a flow and performance comparison for a street car, but for racing tune I think that’s been done.
Between adjustments you need to rev the engine long enough to clear any pooled fuel out of the intake manifolds. If you don't do that it will always seem to be running rich.
Maybe I’m confused…but righty tighty, lefty loosy is the normal configuration for most screws. So, by turning them counter clockwise, your loosening the screws, bringing them up and making the carbs richer. Older ZS carbs are adjusted from the bottom, therefore this left lean, right rich theory is correct, but these are adjusted from the tops. I’d try going in (right) instead of out (left) to correct the rich condition.
On the ZS that are adjusted from the bottom you actually adjust the position of the jet. Here the jet is stationary and we are adjusting the needle position. The needle is held to the piston by the adjusting screw. The screw can turn, but can not move up and down, it is always at the same position in relevance to the piston. Therefore the needle moves up and down instead. So by loosening the screw from the top we move the needle down and closing the gap between the needle and the jet. By tightening the screw we are pulling the needle up and opening more room for the fuel to come through the jet.
That's frustrating.. Trying to make a silk purse out of a sows ear .. I never liked Strombergs.. I think BL went for them instead of SU's because of price. The engine and carb rebuild should get you to a decent compromise. The cam timing (as I've seen you do expertly), will help..
Elin, after so many changes to the mixture, why did you not check the air flow balance again? What does blipping the throttle do for you? This style of video is great, thank you for adopting this video technique.
The needles are spring biased in a particular direction wearing the needle seat oblong. Pull the lids and pistons and check the fixed needle seats for concentricity. If the needle seats are worn oblong no amount of adjusting will lean the carbs out. The needle seats are available from Joe Curto or Burlen. These seats are pressed in/out of the carb bodies. Note the height (measured from the pedestal) they’re pressed in the body before removal. I had a ‘75 MGB that I commuted 140 miles a day in. The car had a single Zenith installed. Loved that car, hated having to pass California smog every year! I pressed in a new fixed seat every couple of years and always passed my smog test with flying colors. ….. just a thought. Burlen LTD web site also has some tech docs that might be helpful.
I appreciate the clear demonstration of lifting the air valve and how to interpret that.
A friend of mine just bought a '74 TR6 and it has some carburetor issues that I am going to look into. I'm good at Weber and most US carbs but have never worked on Zenith Strombergs. Thanks for the introduction on tuning.
Great video...I needed an update as I have not done this in 50 years...
I had my carbs rebuilt by 'Poolboy' from the 6-Pack forums. I was new to Stroms and attempted to tune them to take care of a bad stumble that developed, and it just got worse. Plus, they looked horrible, lots of corrosion. Just before I sent them off, I realized that the actual problem was me- I had re-gapped the plugs to around .035 IIRC, and they gummed up on the last drive I took. I forgot about my experiment and messed up my carb tuning! New plugs conservativly gapped solved the problem, but I still wanted fresh carbs and sent them to Poolboy anyway LOL. Carbs take a lot of practice...
Now you know why they named a James Bond villain Stromberg!
Thanks for the great job very quick nice and clean. Appreciate the way to explain tings 🇩🇰👍👌
That screwdriver trick is great.
That’s a pretty tired engine, so those are probably pretty tired needles and valves. Specs are online. In defence of Zenith Stromberg carbs, I’ve got twin SUs 1.5, twin Strombies 1.5 and twin Strombies 1.25 for my 1500. My first choice is the Strombies for reliability and stability. Someday I’ll get around to doing a flow and performance comparison for a street car, but for racing tune I think that’s been done.
Good to see you again - Happy New Year to you and your family.
I still have the carb adjustment tool from my days mucking about with a Spitfire.
Between adjustments you need to rev the engine long enough to clear any pooled fuel out of the intake manifolds. If you don't do that it will always seem to be running rich.
As always you show and describe everything your doing, and why. Can you do one on tuning dual webers? Great videos
Maybe I’m confused…but righty tighty, lefty loosy is the normal configuration for most screws. So, by turning them counter clockwise, your loosening the screws, bringing them up and making the carbs richer. Older ZS carbs are adjusted from the bottom, therefore this left lean, right rich theory is correct, but these are adjusted from the tops. I’d try going in (right) instead of out (left) to correct the rich condition.
On the ZS that are adjusted from the bottom you actually adjust the position of the jet. Here the jet is stationary and we are adjusting the needle position. The needle is held to the piston by the adjusting screw. The screw can turn, but can not move up and down, it is always at the same position in relevance to the piston. Therefore the needle moves up and down instead. So by loosening the screw from the top we move the needle down and closing the gap between the needle and the jet. By tightening the screw we are pulling the needle up and opening more room for the fuel to come through the jet.
Ah….that explains it! I knew I was confused! Thanks!
That's frustrating.. Trying to make a silk purse out of a sows ear .. I never liked Strombergs.. I think BL went for them instead of SU's because of price. The engine and carb rebuild should get you to a decent compromise. The cam timing (as I've seen you do expertly), will help..
I'm still here..El Guapo!!
Elin, after so many changes to the mixture, why did you not check the air flow balance again? What does blipping the throttle do for you? This style of video is great, thank you for adopting this video technique.
I too enjoy this technical education video. Keep up the good work!
You need to reset the height of the float. Or replace the carburetors SUs like did in my MG.
Where do you get the air-flow indicator and the needle adjuster devices please?
mossmotors.com/triumph-tr6-250/car-care-garage-tools/tools/carburetor-synchronizer-tool
mossmotors.com/triumph-tr6-250/car-care-garage-tools/tools/tool-carb-adjusting
Are these Stock or Upgrade carbs??
What is the Upgrade carb choice??
Is this Harder than Tuning a Stratavarius??
You're chasing your tail... trying to fettle a dodgy engine... inevitable decision unfortunately reached to refresh / rebuild it .
EFI conversion. 😉😅