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Cold starting problem - twin 1.5 inch Cooper S
https://www.ausmini.com/forums/viewtopic.php?f=2&t=98707		 Page 1 of 1
Author:  belldane [ Fri Jun 21, 2019 5:41 pm ]
Post subject:  Cold starting problem - twin 1.5 inch Cooper S
Every winter is the same. Pull choke out as far as it will go and after many cranks and nearly running battery flat it will start. Once warm, first click of the key and no problems. I reckon the problem is not getting enough choke. I could adjust the choke cable but is there an adjustment screw to make chokes open further? Any help most wellcme.
Author:  9YaTaH [ Fri Jun 21, 2019 7:14 pm ]
Post subject:  Re: Cold starting problem - twin 1.5 inch Cooper S
As I understand it, the choke closing is set during body assembly. So adjusting the slack out of the cable will only work up to a point...check how far the choke(s) are closing first...on a car I have, they only close by about 2/3rds...(that seems to work fine, don't know if you would really want a fully closed choke with an SU anyway)...
Author:  IndigoBlueCooperS [ Sat Jun 22, 2019 9:28 am ]
Post subject:  Re: Cold starting problem - twin 1.5 inch Cooper S
Have you checked that when you pull the choke out all the way, that the main jets pull down from the bottom of the carby? They should come down about 1/4" or so. You will see the brass of the jet. This will give more fuel for the cold start. Otherwise you may be only getting the fast idle with the choke on and no extra fuel.
Author:  Bill B [ Sat Jun 22, 2019 11:09 am ]
Post subject:  Re: Cold starting problem - twin 1.5 inch Cooper S
The lever that moves the jet for cold start has a lot of cable travel BEFORE actually moving the jet down. Like IndigoBlueCooperS says, the first part of the lever movement is to allow the idle speed to be increased.
I had the same issues with 1-1/2" SUs until I richened the mixture by 2 flats, which has improved cold starts.
Author:  phillb [ Sat Jun 22, 2019 1:41 pm ]
Post subject:  Cold starting problem - twin 1.5 inch Cooper S
9YaTaH wrote:
As I understand it, the choke closing is set during body assembly. So adjusting the slack out of the cable will only work up to a point...check how far the choke(s) are closing first...on a car I have, they only close by about 2/3rds...(that seems to work fine, don't know if you would really want a fully closed choke with an SU anyway)...


SU’s don’t work that way. There is no “choke” that closes. They are different to most other carbs. The jet drops down to increase the amount of fuel instead.

As mentioned already I would say also that your jets are not dropping as they should. Watch the jets while someone pulls out the choke fully. There are usually 2 stages, a small cam increases idle, then a lever makes the jet move down.


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Author:  9YaTaH [ Sat Jun 22, 2019 2:33 pm ]
Post subject:  Re: Cold starting problem - twin 1.5 inch Cooper S
:roll:
phillb wrote:
9YaTaH wrote:
As I understand it, the choke closing is set during body assembly. So adjusting the slack out of the cable will only work up to a point...check how far the choke(s) are closing first...on a car I have, they only close by about 2/3rds...(that seems to work fine, don't know if you would really want a fully closed choke with an SU anyway)...


SU’s don’t work that way. There is no “choke” that closes. They are different to most other carbs. The jet drops down to increase the amount of fuel instead.

As mentioned already I would say also that your jets are not dropping as they should. Watch the jets while someone pulls out the choke fully. There are usually 2 stages, a small cam increases idle, then a lever makes the jet move down.


Ummmm Yeah...my jets are only dropping 2/3rds of what they are capable of doing :roll:
Author:  Lc99g [ Sun Aug 25, 2019 6:45 pm ]
Post subject:  Re: Cold starting problem - twin 1.5 inch Cooper S
Check your plug gaps. Likely too wide.
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