Register Login
im Axle Specialists
Reply
 
Thread Tools Search this Thread
Old 05-08-2010   #1
Join Date: Aug 2009
Posts: 13
Thanks: 0
Trader Rating: 0
United Kingdom 
Carburettor help please

Hi all,
Wife complaining (unusual!) today re her car having no power.
Tried it and found that it appeared to be firing on one cylinder!.....removed plugs and both very sooty. cleaned and refitted and engine ran fine.
Thought i would look at carb, found slow running jet partially blocked so cleaned and refitted, adjusted idle speed (Generator light just flickering as per Haynes) BUT when trying to adjust mixture screw, no difference all the way in or out! removed screw, needle has a flat end, is this correct? should it not be a sharp point (it does taper down at the end but has a distinct flat face) as with other carbs i have messed with?
Any help appreciated.
Regards, Graham
__________________
FIAT Forum Useful Links:
Donate to FF | Buy FF Merchandise | Classifieds | FF Insurance | How-to Guides

nerodino is offline Reply With Quote Quote 
Old 06-08-2010   #2
Shed Troglodyte
 
Bambino's Avatar
Join Date: Aug 2009
Location: Sunshine Coast, Australia
Posts: 1,497
Thanks: 105
Trader Rating: 0
Bambino has donated!
Australia 
Re: Carburettor help please

Quote Originally Posted by nerodino View Post
needle has a flat end, is this correct? should it not be a sharp point (it does taper down at the end but has a distinct flat face) as with other carbs i have messed with?
Any help appreciated.
Regards, Graham
Graham,

I've attached a photo of a new and an old IMB idle screw. Yes, it does have a sharpish point though it is the taper that does most of the work in regulating the idle mixture. If yours is so flat that the taper is missing most of its length, then the screw is useless.

I'd wonder how tightly the screw had been fitted in the past as these ones do not have a collar and seat that are supposed to prevent damage to the taper. The second set of idle screws in the pictures are from a DCOE carby and show the new style with a collar and the old style, like yours, with just a naked taper.

If you rebuild the carby, you will get a new idle screw as part of the rebuild kit. BTW, unfortunately the old style and new collared screws are not interchangeable. The collared screw has a much finer taper and point to allow tighter control of the idle mixture in the newer 'anti-pollution' carburettors.

Chris
Attached Thumbnails
Click image for larger version

Name:	Idle screw.jpg
Views:	13
Size:	49.3 KB
ID:	80842   Click image for larger version

Name:	DCOE idle screws.jpg
Views:	16
Size:	64.5 KB
ID:	80843  

__________________
1967 Fiat 500F (Enzino)
Sundry other Italian rotboxes

Amante di vecchie automobili italiane
Bambino is offline Reply With Quote Quote 
Old 06-08-2010   #3
Join Date: Aug 2009
Posts: 13
Thanks: 0
Trader Rating: 0
United Kingdom 
Re: Carburettor help please

Nice work bambino, Mine is a collared type as depicted in r/h photo
(l/h screw of the two) It appears to have a sharp point which mine has not. Having said that the taper is there, it is only the first 0.25mm or maybe less which is flat.
I guess the best thing to do is buy a carburettor repair kit from Ricambi.
Regards, Graham.

Quote Originally Posted by Bambino View Post
Graham,

I've attached a photo of a new and an old IMB idle screw. Yes, it does have a sharpish point though it is the taper that does most of the work in regulating the idle mixture. If yours is so flat that the taper is missing most of its length, then the screw is useless.

I'd wonder how tightly the screw had been fitted in the past as these ones do not have a collar and seat that are supposed to prevent damage to the taper. The second set of idle screws in the pictures are from a DCOE carby and show the new style with a collar and the old style, like yours, with just a naked taper.

If you rebuild the carby, you will get a new idle screw as part of the rebuild kit. BTW, unfortunately the old style and new collared screws are not interchangeable. The collared screw has a much finer taper and point to allow tighter control of the idle mixture in the newer 'anti-pollution' carburettors.

Chris
__________________
FIAT Forum Useful Links:
Donate to FF | Buy FF Merchandise | Classifieds | FF Insurance | How-to Guides


Last edited by nerodino; 06-08-2010 at 18:42.
nerodino is offline Reply With Quote Quote 
Old 07-08-2010   #4
Shed Troglodyte
 
Bambino's Avatar
Join Date: Aug 2009
Location: Sunshine Coast, Australia
Posts: 1,497
Thanks: 105
Trader Rating: 0
Bambino has donated!
Australia 
Re: Carburettor help please

Quote Originally Posted by nerodino View Post
Having said that the taper is there, it is only the first 0.25mm or maybe less which is flat.
I guess the best thing to do is buy a carburettor repair kit from Ricambi.
Regards, Graham.
A new kit is the go - especially as the carby will have to be stripped to be cleaned.

I've attached a photo of the idle screw out of an IMB 10 from a later model 650cc 126 engine next to the older style screw out of a 500F IMB 6. The screw end is collared, has a flat tip and only a slight taper.

The idle mixture screw on these later carbies in contained in a well and sealed with an O-ring, presumably to protect the threads from dirt - or maybe, to discourage amateurs like me from tampering with the setting

Good luck with the rebuild,

Chris
Attached Thumbnails
Click image for larger version

Name:	IMB 10 idle screw.jpg
Views:	10
Size:	122.8 KB
ID:	80879  
__________________
1967 Fiat 500F (Enzino)
Sundry other Italian rotboxes

Amante di vecchie automobili italiane
Bambino is offline Reply With Quote Quote 
Old 07-08-2010   #5
Join Date: Aug 2009
Posts: 13
Thanks: 0
Trader Rating: 0
United Kingdom 
Re: Carburettor help please

Chris, Let me get this right, You say the right hand screw is froma 650 engine? Mine is a 500 but definately has the collared screw on the right in the carb!
Also i note that that screw DOES HAVE a very small flat at the taperof the needle as has mine.
I wonder if mine has the wrong carb, How can i tell?
Regards,Graham


Quote Originally Posted by Bambino View Post
A new kit is the go - especially as the carby will have to be stripped to be cleaned.

I've attached a photo of the idle screw out of an IMB 10 from a later model 650cc 126 engine next to the older style screw out of a 500F IMB 6. The screw end is collared, has a flat tip and only a slight taper.

The idle mixture screw on these later carbies in contained in a well and sealed with an O-ring, presumably to protect the threads from dirt - or maybe, to discourage amateurs like me from tampering with the setting

Good luck with the rebuild,

Chris
__________________
FIAT Forum Useful Links:
Donate to FF | Buy FF Merchandise | Classifieds | FF Insurance | How-to Guides

nerodino is offline Reply With Quote Quote 
Old 07-08-2010   #6
Shed Troglodyte
 
Bambino's Avatar
Join Date: Aug 2009
Location: Sunshine Coast, Australia
Posts: 1,497
Thanks: 105
Trader Rating: 0
Bambino has donated!
Australia 
Re: Carburettor help please

Graham,

From the information I have, Fiat fitted the following Weber carbies as standard equipment to the following cars -

Nuova 500: 26 IMB 1
500 Sport: 26 IMB 3
500D: 26 IMB 4
Wagon: 26 OC (basically a side draft IMB)
500F: 26 IMB 6
500L: 26 IMB 10 (also fitted to the 126s)

The major differences were in the jetting and on later models, the presence of anti-pollution 'CO limiters' and fuel return lines. My 1968 500F has an IMB 6 and the 1990 126 (650cc) I bought for parts had an IMB 10.

The type is stamped on the side. I would think that your carby is probably correct for your car, particularly if it is a late model. If you are going to change carbies, you would probably not replace one IMB with another (they are not that great) - more like you'd change it for a Weber 30 DIC or a Dell'Orto FZD.

Hope this helps,

Chris
__________________
1967 Fiat 500F (Enzino)
Sundry other Italian rotboxes

Amante di vecchie automobili italiane
Bambino is offline Reply With Quote Quote 
Old 07-08-2010   #7
Join Date: Aug 2009
Posts: 13
Thanks: 0
Trader Rating: 0
United Kingdom 
Re: Carburettor help please

You are correct Chris, It has a 26 IMB 6 as should have,
Maybe i will look to change it!
Graham


QUOTE=Bambino;2553091]Graham,

From the information I have, Fiat fitted the following Weber carbies as standard equipment to the following cars -

Nuova 500: 26 IMB 1
500 Sport: 26 IMB 3
500D: 26 IMB 4
Wagon: 26 OC (basically a side draft IMB)
500F: 26 IMB 6
500L: 26 IMB 10 (also fitted to the 126s)

The major differences were in the jetting and on later models, the presence of anti-pollution 'CO limiters' and fuel return lines. My 1968 500F has an IMB 6 and the 1990 126 (650cc) I bought for parts had an IMB 10.

The type is stamped on the side. I would think that your carby is probably correct for your car, particularly if it is a late model. If you are going to change carbies, you would probably not replace one IMB with another (they are not that great) - more like you'd change it for a Weber 30 DIC or a Dell'Orto FZD.

Hope this helps,

Chris[/QUOTE]
__________________
FIAT Forum Useful Links:
Donate to FF | Buy FF Merchandise | Classifieds | FF Insurance | How-to Guides

nerodino is offline Reply With Quote Quote 
Reply
Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump
Similar Threads
Thread Thread Starter Forum Replies Last Post
(T) 127 Carburettor Polistil 127 127 4 12-06-2009 21:06
(G) Carburettor Robot Ducato 0 25-07-2007 09:13
(G) uno 45 S carburettor - premrajeev Uno 4 15-01-2007 09:24
Carburettor tuning... fiat1100d Lets Talk FIAT 4 04-09-2006 13:53
(T) 1.6 Carburettor Trancendental Tipo (Classic) 0 10-01-2006 03:09