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Carb settings after rebuild - Throttle Levers and Spindle Questions

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Matts67spit Avatar
Matts67spit Matt Burrow
Phoenix, AZ, USA   USA
1967 Triumph Spitfire MkII "Silver Bullet"
Hi All,

I've been working on adjusting my twin carbs after I performed the rebuild and I've got some questions. Would love your help.

First, a few things that I have done:

1. When inserting the valves I performed the 'click test' and both carbs did great.
2. I then fully tightened the jet adjustment nuts, and followed up by backing them off 12 faces. (Thanks to those who helped me with this, in a different, earlier thread).

After I performed these 2 adjustments the engine turned over on the 1st crank, and hummed along VERY well. Tach said that engine was at 2,200 RPM,..but the idle didn't sound high. (a few folks told me that the Tach may be off,..so am not 100% sure of those 2,200 rpms).

I then started to work with the Throttle Speed Screws to adjust the RPM's.

As I worked on things I found several issues. I didn't notice these during the carb rebuild, mainly because I didn't know all of the carb part relationships. Only after I put things back together and started tuning it have I come to understand more about what each part does.

1. The 2 levers (one for each carb) that attach to the Throttle Spindle don't line up with each other when the throttle valve plates are fully closed. (See picture - the red line shows the location of the lever for the front carb, and the yellow box highlights the lever for the rear carb, it is rotated closer to the passenger side of the car.)
a) The lever for the rear carb can't be pushed back to the driver's side to align with the front lever.
b) When I pull the front lever towards me (towards the passenger side) to align it with the rear carb lever, the result is the front throttle valve plate being open a crack, while the rear throttle valve plate
is closed. They are not in synch. How do I get these 2 levers to align?

2. The lever associated with the rear carb is hard to rotate on the throttle spindle. The lever on associated with the front carb moves freely and easily.
a) How easily should these levers move?
b) any idea on how to loosen up the rear lever? (I tried PB Lithium Grease,..but that didn't really help much).

3. The 2 Throttle Return Springs are not the same. The previous owner had a 'sprung' spring for the rear carb, and a tight/newer spring on the front carb. I know I should get new matching springs.
a) Any idea where to best get the springs?
b) What tension level of spring should I get, or does it matter, as long as the 2 are identical? (I'm thinking it DOES matter, but can't find any info for this)

Thanks guys. I appreciate the help!

Matt

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Attachments:
throttle levers off alignment.jpg    42 KB
throttle levers off alignment.jpg

throttle return springs .jpeg    45.6 KB
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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"
All the nuts on the connecting rod between the two carbs have to be loose so you can line up the throttle plates. Once the plates are in the same plane then you can adjust the levers. You want them close to opening the throttle but not touching. I'm not sure of HS2s, but it looks like you're missing a few pieces for the throttle cable and return springs.



'S all for now
Vic

spitfire50 Avatar
spitfire50 Paul Mugford
Rochester, N.H., USA   USA
In reply to # 1505654 by carChips All the nuts on the connecting rod between the two carbs have to be loose so you can line up the throttle plates. Once the plates are in the same plane then you can adjust the levers. You want them close to opening the throttle but not touching. I'm not sure of HS2s, but it looks like you're missing a few pieces for the throttle cable and return springs.

Victor,
No throttle cable. mechanical linkage.
All the best,
Paul

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spitfire50 Avatar
spitfire50 Paul Mugford
Rochester, N.H., USA   USA
In reply to # 1505649 by Matts67spit Hi All,

I've been working on adjusting my twin carbs after I performed the rebuild and I've got some questions. Would love your help.

First, a few things that I have done:

1. When inserting the valves I performed the 'click test' and both carbs did great.
2. I then fully tightened the jet adjustment nuts, and followed up by backing them off 12 faces. (Thanks to those who helped me with this, in a different, earlier thread).

After I performed these 2 adjustments the engine turned over on the 1st crank, and hummed along VERY well. Tach said that engine was at 2,200 RPM,..but the idle didn't sound high. (a few folks told me that the Tach may be off,..so am not 100% sure of those 2,200 rpms).

I then started to work with the Throttle Speed Screws to adjust the RPM's.

As I worked on things I found several issues. I didn't notice these during the carb rebuild, mainly because I didn't know all of the carb part relationships. Only after I put things back together and started tuning it have I come to understand more about what each part does.

1. The 2 levers (one for each carb) that attach to the Throttle Spindle don't line up with each other when the throttle valve plates are fully closed. (See picture - the red line shows the location of the lever for the front carb, and the yellow box highlights the lever for the rear carb, it is rotated closer to the passenger side of the car.)
a) The lever for the rear carb can't be pushed back to the driver's side to align with the front lever.
b) When I pull the front lever towards me (towards the passenger side) to align it with the rear carb lever, the result is the front throttle valve plate being open a crack, while the rear throttle valve plate
is closed. They are not in synch. How do I get these 2 levers to align?

2. The lever associated with the rear carb is hard to rotate on the throttle spindle. The lever on associated with the front carb moves freely and easily.
a) How easily should these levers move?
b) any idea on how to loosen up the rear lever? (I tried PB Lithium Grease,..but that didn't really help much).

3. The 2 Throttle Return Springs are not the same. The previous owner had a 'sprung' spring for the rear carb, and a tight/newer spring on the front carb. I know I should get new matching springs.
a) Any idea where to best get the springs?
b) What tension level of spring should I get, or does it matter, as long as the 2 are identical? (I'm thinking it DOES matter, but can't find any info for this)

Thanks guys. I appreciate the help!

Matt
Matt,
A close look at the spot where the linkage connects to the carb will show a lever on the carb that has a forked end and another lever on the linkage that has a pin or tab that fits between the sides of the fork. When all is correctly set the pin won't be against either side of the fork at closed throttle. As the linkage moves to open the throttles the pins on both ends of the linkage will contact the lower side of their respective forks at the same time. You start with the linkage not operating the carbs and set the idle and balance the airflow first. Then you set the linkage levers so the pins are between the sides of the forks as I described above,
Looking at the interconnecting shaft between throttles you will see a "spare" lever. Positioned correctly that serves as a closed throttle stop for the linkage preventing it from pushing against the carb forks. The last bit of closing of the carbs is done by the throttle return springs. The spring on the left in your pic is the correct one for a Mk2 Spitfire. These springs only have to be strong enough to shut the carb throttles. More strength will make them wear the throttle shafts and the bushings faster. The main linkage has a separate spring returning it to closed throttle oposition. That spring can be stronger without wearing the carbs unnecessarily.
All the best,
Paul

Matts67spit Avatar
Matts67spit Matt Burrow
Phoenix, AZ, USA   USA
1967 Triumph Spitfire MkII "Silver Bullet"
Thanks so much guys,

Paul - I see where you are coming from, and understand the steps you are describing,..but I am still having an issue getting the 2 levers to get to the same starting point, where they are aligned and the throttle valves plates are closed.

Looking at the picture, I loosened every one of the bolts (1-5,..especially # 1, thinking that this would release the lever to then allow it to rotate on the throttle spindle) and was not able to get the rear carb lever pushed back towards the driver's side of the car, to align with the front carb lever. In the picture you will see the rear carb lever has space (yellow line) before touching the cam, and the front lever rests right up against it (yellow 'X').

Do I need to disassemble the carbs, pull out the throttle spindle from the end nut (#1) of the rear carb and then turn, and re-seat it in the nut?

I'm a little befuddled, as you can tell.....

Thanks for your help!

Matt


Attachments:
levers still out of alignment .jpeg    47 KB
levers still out of alignment .jpeg

65or66 Gold Member Jim B
Lake village, IN, USA   USA
1965 Triumph Spitfire MkII
1973 Triumph Spitfire 1500 "Jusanudda Munny Pit"
buy a manual?thumbs up

spitfire50 Avatar
spitfire50 Paul Mugford
Rochester, N.H., USA   USA
Matt,
Parts 2,3,4,5 are all on a common shaft. With the bolts loose on them you should be able to turn them on the shaft. You might have to spread the split in them to free them to turn. If you can't get part 2 to turn you can always loosen all of the others and turn the shaft and part 2 to the correct position and work from there, but having the lever 2 move on the shaft is better as then adjusting will go easier.
Part 3 should touch the choke shaft when the throttle is closed. It acts as a throttle closed stop for the mechanical linkage.
There should be a space as at the yellow line between the throttle mechanism and the choke cam. Contact as it seems you have at the yellow x should only happen when the choke control has been pulled a bit.
There should be a bit of end float of the shafts between the carbs. Without it the linkage won't work freely.
Good luck,
Paul

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