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 Posted: Jul 4, 2018 06:20PM
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CA
Just to clarify....the carb at the back of the engine is the right-hand carb  

 

"Everybody should own a MINI at some point, or you are incomplete as a human being" - James May

"WET COOPER", Partsguy1 (Terry Snell of Penticton BC ) - Could you send the money for the unpaid parts and court fees.
Ordered so by a Judge

 

 

 

 Posted: Jul 3, 2018 04:21PM
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Quote:
Originally Posted by thebluepotato
Question around sync'ing dual carbs...
After reading the relevant sections of your SU manual, read the instructions that came with your particular synchronizer. Download a copy if you don't have the original. 

The synchronizers work really well. My carbs were synchronized using the tube/ear method by a "pro." I bought and used a synchronizer and discovered my carbs were significantly out of sync. They're in sync now.

 

Michael, Santa Barbara, CA

. . . the sled, not the flower

      Poser MotorSports

 Posted: Jul 3, 2018 12:23PM
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My second link is not dead, it is just old and has a protection error.  Click the link and when the error message comes up, go to the link address and remove the " https:// " prefix so the link is just WWW.  Then hit enter.

Remember that "rebuilt" does not mean balanced or tuned.  Do not expect that either has been done by a professional rebuilder.  Neither can be done without the carbs installed on your car.

Doug L.
 Posted: Jul 3, 2018 08:38AM
 Edited:  Jul 3, 2018 08:39AM
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Second link you posted is defunct.  But I am looking at the Tech manual....just so much there to digest.

I have been watching this guy for some time now, and this is essentially what I was trying to do (after carbs have been set).  Forgot to say these carbs are 100% rebuilt and set with timing a few weeks ago....it was the amount of vac I felt with the left carb that got me worried about the balance between the two.  It was that noticable.

Skip ahead to 19:48

/// Basil - 1974 Mini 1000 /// THE BLOG: www.thebluepotato.net/blog

 Posted: Jul 3, 2018 07:15AM
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Quote:
Originally Posted by thebluepotato
 
....that also includes the individual idle adjust screws?  Those look independent on each SU body - again, I am just learning about these carbs.  And enjoy learning.
Yes, with the linkages disconnected and lose you adjust each idle screw independently to set the air flow for each carb.  

Don't take this wrong but you really need to read through your service manual while looking at the carb(s) to understand the adjustments.  Don't try adjustments without reading through things at least once.  If you don't have a carb manual or if your service manual doesn't have a section on carb adjustments, see the two websites linked below.

Click on the "technical" tab at the top of the page linked below.
//sucarb.co.uk/technical-su-carburetters

Assuming you are dealing with HS carbs, read over the PDF manual linked below.
//www.1978mgmidget.com/Tuning_SU_Carbs.pdf

Doug L.
 Posted: Jul 3, 2018 06:58AM
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If you have the linkages on upside down they are a pita, the adjusting nuts should be facing up. 

As long as you have a little play in the throttle cable you can just loosen up one side. Yes you need to adjust the idle screws to get them in synch.

Also block off the vacuum line nipple on the carb if you are not using it.

If in doubt, flat out . Colin Mc Rae MBE 1968-2007.

 Posted: Jul 3, 2018 06:24AM
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Quote:
Originally Posted by dklawson
Quote:
Originally Posted by thebluepotato
 
... So maybe I need to disconnect all the linkages.  What a PITA.

...  Pissed.
Sorry.  That's just the way it is and the way it is done.  Each carb has its airflow adjusted independently, then the linkages tie them together.
....that also includes the individual idle adjust screws?  Those look independent on each SU body - again, I am just learning about these carbs.  And enjoy learning.

/// Basil - 1974 Mini 1000 /// THE BLOG: www.thebluepotato.net/blog

 Posted: Jul 3, 2018 05:59AM
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Quote:
Originally Posted by thebluepotato
 
... So maybe I need to disconnect all the linkages.  What a PITA.

...  Pissed.
Sorry.  That's just the way it is and the way it is done.  Each carb has its airflow adjusted independently, then the linkages tie them together.

Doug L.
 Posted: Jul 3, 2018 04:40AM
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Quote:
Originally Posted by dklawson
Sort of mentioned in the posts above is that you set the idle balance with the throttle and choke linkages 100% lose.  Once the linkages are disconnected so the carbs are not tied to each other you set each carb's airflow using the meter.  Once that is done you set the throttle linkages so there is a bit of throttle pedal/cable travel before the butterfly shafts start to move and so they "pick up" at the same time.

As stated above it's easier to show than to write out.  Read over your service manual again then visit the technical pages for the SU carbs at burlen.co.uk  YouTube surely will have some good examples of how to adjust SU carbs.

I have never been good setting the carbs using the hissing hose method.  I prefer meters but have used pointing wires when in a pinch.
Thanks - I guess this is a bit more complicated than using an STE Syncrometer and simply adjusting the idle speed on each carb.  The left carb is definately pulling a LOT more air into the venturi than the right and even when I adjust the idle screw on the right, it does not change the idle speed.  One on the left changes when I adjust the idle screw.  So maybe I need to disconnect all the linkages.  What a PITA.

And yes, MED dual stack setup.  Liking them so far - not thrilled with that large plate, making any adjustments to the SU's is a PITA and need to remove the plate for the major adjustments.  Pissed.

/// Basil - 1974 Mini 1000 /// THE BLOG: www.thebluepotato.net/blog

 Posted: Jul 3, 2018 03:44AM
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Sort of mentioned in the posts above is that you set the idle balance with the throttle and choke linkages 100% lose.  Once the linkages are disconnected so the carbs are not tied to each other you set each carb's airflow using the meter.  Once that is done you set the throttle linkages so there is a bit of throttle pedal/cable travel before the butterfly shafts start to move and so they "pick up" at the same time.

As stated above it's easier to show than to write out.  Read over your service manual again then visit the technical pages for the SU carbs at burlen.co.uk  YouTube surely will have some good examples of how to adjust SU carbs.

I have never been good setting the carbs using the hissing hose method.  I prefer meters but have used pointing wires when in a pinch.

Doug L.
 Posted: Jul 2, 2018 08:46PM
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GB
I've got a collection of airflow meters and all of them without exception are better than the unscientific pipe method.  Tigger was tuned by a 'Name' a few years ago using his pipe with a whistle in it to make it "even more accurate", and the video evidence of how far out it was is not good viewing.  I've tried it a few times and remain entirely unconvinced, to the point that fingers over the carb mouth is probably more accurate.  Having said that, close enough is good enough for some things.

Doing and showing carb balancing is always easier than trying to write an explanation, but the gist is that you need to pull the dashpots off and ensure that both jets are the same distance down from the bridge (vernier caliper is ideal for this), undo all the cross linkages (making sure the springs don't ping), set up the carbs to suck equally on the synchrometer, do the linkages back up, recheck the airflow at tickover and 2500rpm.

MED stubstack setup ?

 Posted: Jul 2, 2018 04:42PM
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I was taught many years ago to use a 2 foot piece of fuel hose held up to my ear and listen for the hiss then adjust them equally, still do it the same way and never had any issues.

Any carb adjustments need to be done with the carbs in good shape especially the throttle shafts on HS2's as they are not bushed and wear and leak air and there is no way you can tune them successfully with air leaks.

If in doubt, flat out . Colin Mc Rae MBE 1968-2007.

 Posted: Jul 2, 2018 12:11PM
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I'd suggest you back off the nuts on the arms that connect the two carbs. then adjust each carb by the idle screw till rpm desired and the pair are sucking the same. Then lock the two back together. I'd also suggest you check that both jet tubes are at the same height. I like your air horns and air cleaner assembly. Steve (CTR)

 Posted: Jul 2, 2018 11:35AM
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Question around sync'ing dual carbs.  First, not sure if it is the nature of dual carbs for the one at the back of the engine (i.e. left hand carb) to pull more vac (by feel/palm of hand) than say the right hand side carb....or is it?

That is what is happening with my SU2's....so I grabbed a syncrometer and the balance is way off between the two readings.  Adjusted the right hand via the idle screw and car idles much more smoother now, but balance still off by the numbers.

Has anyone balanced a pair with a syncrometer and if so, any general advice?

/// Basil - 1974 Mini 1000 /// THE BLOG: www.thebluepotato.net/blog