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thompson
United Kingdom
114 Posts |
 Posted - 17/01/2017 : 17:39:49
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Has anyone got two one inch SU carbs...? I only need the carbs to replace mine that are worn and thus cannot be adjusted properly...
Like these...Thanks in advance...Tom
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bloodysalmon
Spain
1482 Posts |
Posted - 17/01/2017 : 17:56:16
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Hi Tom, I've just been working on my 1" twin carbs for my F; It's taken time testing and adjusting but I have finally get there. So my question is why do you think they are worn, and which part is it that is worn? There are so many components within them that just 1 piece could be offsetting your efforts to be tuned.
Please explain this issue to see if we can help more.
Chris Blood (D0407 & F0753) |
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thompson
United Kingdom
114 Posts |
Posted - 17/01/2017 : 18:32:51
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Hi Chris....
We have replaced every part on the carbs ( with a pricey kit from Burlen) and the brass flaps have worn the inside of the carbs...you can see light coming in when they are closed and thus they are drawing too much air - hence we cannot adjust them. If it was just the flaps then these could be filed to fit but its isn't...!
Ps...I am not a mechanic and am just relaying what the chap who is working on the car tells me hence maybe I am using the wrong vocabulary ...! |
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PeterL
United Kingdom
1731 Posts |
Posted - 17/01/2017 : 19:10:20
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I possibly have a pair of bodies...
Will have a look sometime in the next few days. Remind me if you hear nothing...
Cheers
P |
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Simon Johnston
United Kingdom
6205 Posts |
Posted - 17/01/2017 : 19:36:11
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Tom,
The chances are that an old bodies you get will also be equally worn. Time to bite the bullet (again!) and buy new ones? They are now made of aluminium alloy rather than mazak and are altogether much better than the old ones.
Simon J
J3437 |
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bloodysalmon
Spain
1482 Posts |
Posted - 17/01/2017 : 19:54:08
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Ok Tom, what Simon is saying is of course perhaps the right thing to do ... if it is the body only! Buy new as most if not all 80+ year old ones are going to be worn (may work out cheaper in the long run) ... then again, mine weren't and close lovely with new flaps and seals etc ... sounds like Peter can help you too
just had a thought, are you using M5 or M6 needles? ... and why?
Chris Blood (D0407 & F0753) |
Edited by - bloodysalmon on 17/01/2017 19:55:11 |
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thompson
United Kingdom
114 Posts |
Posted - 17/01/2017 : 20:22:40
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| Hi Chris...not sure which needles are being used but yes its only the bodies that are worn. I think that I will do what Simon has suggested as we'll never be able to set the car up properly if we are fighting with worn carbs... |
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Simon Johnston
United Kingdom
6205 Posts |
Posted - 17/01/2017 : 21:14:31
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Of course if you buy new bodies, then you'll need new spindles and possibly butterflies (the flaps)! Did we forget to mention that this is a never ending process? 
Simon J
J3437 |
Edited by - Simon Johnston on 17/01/2017 22:13:51 |
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Westbury
United Kingdom
2061 Posts |
Posted - 17/01/2017 : 22:14:37
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A good machinist should be able to bore and bush the bodies for you thus salvaging your original carburettors and could also be cheaper in the long run.
Chris |
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thompson
United Kingdom
114 Posts |
Posted - 17/01/2017 : 22:32:05
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Thanks Chris....
Has anyone done this to their carbs...?
Not being an engineer I am just wondering how a carb can be made bigger so that the butterflies fit correctly...? |
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Simon Johnston
United Kingdom
6205 Posts |
Posted - 17/01/2017 : 22:36:07
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Tom,
I think Chris was referring to bushing the holes for the spindles which is fairly straightforward. Burden themselves offer this service although from memory it's not cheap.
To my mind, a bit of wear round the butterflies would only be a problem if you couldn't get the idle set correctly. A gap here won't alter the mixture as that has been set further up the carb at the needle. The real problem is air getting in round the spindles which will alter the mixture.
Simon J
J3437 |
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bloodysalmon
Spain
1482 Posts |
Posted - 18/01/2017 : 08:07:45
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this is what and why I was asking Tom! Simon has restated that there are a number of issues to be found that can be impacting the smooth running ... the needles are especially vulnerable ... so please recheck the needles; determine what they and to whether they are in any way bent. Take one out and try the roll-on-flat-surface test just like you do with a snooker cue.
Chris Blood (D0407 & F0753) |
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thompson
United Kingdom
114 Posts |
Posted - 18/01/2017 : 15:53:49
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Hi Chris,
The problem we have is the idling.
It is way too fast. However we can't bring it down as the carbs are letting in too much air because there are gaps around the butterflies when they are closed. The gaps are there because they have worn the inside of the carb....
Chris if you have any ideas how we can get around this then feel free to get in touch...!
Otherwise a new set of carbs (if anyone has a pair please get in touch....) |
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Robin Macmillan
United Kingdom
415 Posts |
Posted - 18/01/2017 : 17:58:51
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Is it possible that the butterfly discs have been fitted the wrong way around. The edge of the disc is champhered to form a seal, if the wrong way round the butterfly disc will probably not close fully. The disk is fully closed when about 80degrees to the vertical
It is hard to imagine how such discs or the casting can "wear" as the are not really any moving parts. The spindle and bearings the spindle runs through do of course wear and can make things floppy.
PB 0527 |
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bloodysalmon
Spain
1482 Posts |
Posted - 18/01/2017 : 18:47:35
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... this is what I was thinking Robin, the amount of contact from the butterflies to the body is so minimum ... got to be worth another look Tom! I did get some of this set quite wrong the 1st too so no shame in re-checking.
If, and only if all efforts have been exhausted by yourself ... I just may have a pair of SU 617T's 1" complete carbs available ... if you dont go down the new route
Chris Blood (D0407 & F0753) |
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thompson
United Kingdom
114 Posts |
Posted - 18/01/2017 : 19:01:41
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Thanks very much....the problem is that I am relaying what my mechanic has said...
So Its good to get some advice from others.
I will mention all this to him and see what he says. The last thing I want to do is chuck some good carbs away...!
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