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Twin HS4 SU carbs, replaced broken throttle spring, now one won't close all the way

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Brakford Avatar
Brakford Stephen Zagorski
Richmond, TX, USA   USA
1975 Triumph 1500 "Sophie"
So I had a throttle spring break on one carb and rev'ing at 2000. Did a quick fix to get me home. Bought a set of new springs and installed.
Ever since, the carb that had the broken spring will not fully close all the time. I switched the springs but no change.
I can rev the car and it will return to almost normal idle or I can manually push it closed and it is at perfect idle.
I cleaned and lubricated the shafts but still cannot get it to close as it should.

Using 20/50 oil is dashpots as I have done for years so don't think that is an issue.

Any suggestions is greatly appreciated.



"Sophie" 1975 Spitfire

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TheZster Avatar
TheZster Steven Z
SAINT LOUIS, MO, USA   USA
1978 Triumph 1500 "BLK-BRY"
I would guess that something in the linkage bent when the spring went loose.... Had a similar issue with one of my webers a while back.... turned out one of the nuts holding the butterfly shafts had picked up a burr - causing it to slightly hang up when closing.....

Good luck -
z

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Tonyfixit Avatar
Tonyfixit Tony M
Duncan, BC, Canada   CAN
Is the throttle cable fully slack?

I am thinking when the spring broke it may have done so after 'hard use' of the throttle, could something be bent or strained?

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carChips Avatar
carChips Victor Harnish
Kelowna, BC, Canada   CAN
1933 MG Magnette
1973 Triumph Spitfire 1500 "Chip"
1989 GMC Sierra 1500 "Bush Truck"
Check the free play on the connecting rod, when the spring broke you probably turned the lost motion lever on the shaft.

https://rimmerbros.com/Item--i-GRID005596

Check the inset.



'S all for now
Vic

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trrdster Avatar
trrdster Wayne Tate
Spencer, NC, USA   USA
1949 Triumph 2000 Roadster
1970 Triumph TR6
1978 Triumph GT6 "Scooter"
1978 Triumph Spitfire "Scooter"    & more
From your write up, I think one of the shafts moved in the clips that hold them in sync, just take some pressure off the one that is sticking and see if it will go back.



Wayne
1970 TR6
2000 Jaguar XK8
1949 Triumph Roadster 2000
1978 Spitfire (rust victim)
1971 GT6 (tarp covered for 12 years, rusted inside out)
1980 Spitfire (getting all the good GT6 parts, all poly suspension and Spax shocks)

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skyking1231 Avatar
skyking1231 Silver Member Frank Strobel
Mt. Sinai, NY, USA   USA
1975 Triumph Spitfire 1500 "Lil' Rose"
have you sync'd up the carbs ?

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Jediscuba Avatar
Jediscuba Steven Spandorf
Southampton, NY, USA   USA
1963 Triumph Spitfire "Pussycat"
1972 Triumph GT6
1980 Triumph Spitfire 1500 "PussyCat The 4th"
I agree with the general consensus. To add to what has already been said, this is a situation that may have existed before the spring broke.
A couple thoughts.
The spring that broke may have not been an original part and was was of higher tension than normal.
This might have supplied enough force to over ride a sticking /binding shaft.

I would suggest that you remove both springs and then loosen the locking devices for both carb shafts.
While the locks are loose check to make sure that the shafts move freely.
Back off the stop screws.
Look at the throttle plates as you turn the shafts.
Put the springs on and see that they have enough tension to close the throttle plates completely
Next set up the engagement position for both the throttle plates and chokes so that they have equal movement.
Using the manual set a basic throttle position so that you may start and run the engine.
Once the engine is warm, follow the manual directions to synchronize the carbs.

If I skipped a step... I apologize.. I don't have a manual at hand.

Steve

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brucejon Avatar
brucejon Gold Member Bruce Jones
Santa Cruz, CA, USA   USA
1960 Triumph TR3A
1963 Triumph TR3B "Tupperware TR3"
1969 Triumph Spitfire MkIII
1972 Triumph TR6
There is also a spring on the linkage that looks like an L. Without it my dual SU setup would not reliably return to idle. See

https://www.moss-europe.co.uk/shop-by-model/triumph/spitfire/fuel-system-induction-controls/carburettors-manifolds/accelerator-choke-controls-spitfire.html



60 TR3A (red), 62 TR3B project, 72 TR6, 69 Mk3 Spitfire EU setup
https://spitfiremk3.wordpress.com

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Brakford Avatar
Brakford Stephen Zagorski
Richmond, TX, USA   USA
1975 Triumph 1500 "Sophie"
I appreciate all the great replies. I loosened all the nuts adjusted the shafts and re-tightened. That seem to do the trick....all is good now.



"Sophie" 1975 Spitfire

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