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 bnicho
A.k.a.: Brett Nicholson
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| posted on May 17th, 2011 at 08:57 AM |
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Sticky Auto Choke
Hi,
I'm having a wierd problem with the auto choke on Olive, my 74 Superbug (stock 1600 DP).
Essentially the choke will turn itself off but won't turn itself on .
Previously when the engine was cold I turned the key, opened the throttle a little and the choke would automatically set itself every time. The car
would start first try and all was happy. Every three months or so I would add a little engine oil to the choke shafts and the choke worked
flawlessly.
Lately the choke has stuck in the off position every time I drive it. When it's cold again I've been forced to open the engine lid and flick the
choke lever by hand to make it work. Otherwise it's difficult to start the car and it runs like a bag of spanners for the first few minutes.
Once moving the choke happily turns itself off (fast idle down to regular idle) as the engine warms up. It just doesn't want to turn itself on
again.
I tried lubricating the shaft on the choke with WD40 and then engine oil and working it back and forth to get it moving.
When that didn't work I pulled the choke element out and the black plastic cap behind. I lubricated the mechanism behind the cap and reassembled,
paying special attenting to hooking the element onto the operating level/pin. I adjusted the choke to the same mark on the carb body I used
previously.
When that didn't work I tried loosening the nut on the end of the shaft and lubricating everything again. Still no joy.
I've had the top off the carb and had a good look. I can't see anything wrong with the choke shaft.
I'm definitely getting 12v to the element.
I'm now thinking perhaps the element is not working correctly. But then surely the choke would stay on (fast idle) all the time rather than not come
on???
Perhaps there is an issue with the choke diaghram??
Any thoughts and suggestions welcomed.
Cheers,
Brett Nicholson
Melbourne, Victoria
1974 VW Superbug L - Olive 
1971 Morris Mini Moke - Mopoke
1966 Austin Mini - Audrey
1965 Morris Mini Traveller - Trixie
2007 Land Rover Freelander 2
2009 Nissan Pathfinder |
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 Bizarre
Super Moderator
The artist formerly known as blue74l
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| posted on May 17th, 2011 at 09:23 AM |
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I have found they can bind
I am guessing the cast body distorts enough to catch the butterfly
If you look down the throat, can you see score marks on the side??
Futue te ipsum!!!
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ratty 63
A.k.a.: Rossco
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| posted on May 17th, 2011 at 10:04 AM |
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I'm not sure about the later carbs, but I had a similar problem with a 28PICT that I had fitted to my '63 Beetle a few years ago...
The brass bush that supports the choke shaft would work its way out of the body of the carb over a period of time and would 'lock' the choke mech in
whatever position it was in at the time. Sometimes the choke would not turn off, but most of the time it would not come on when the engine was
cold.
If you move the stepped idle stop (attached to the choke shaft) by hand when the car is cold does it feel free? It must have almost no resistance.
I'm thinking that once the car is running the heat from the choke element would cause the choke shaft to expand just enough that it becomes loose
enough to shut off by itself....
R 
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bnicho
A.k.a.: Brett Nicholson
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| posted on May 17th, 2011 at 12:53 PM |
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Thanks for the replies.
The spot just off hot-idle definitely has more resistance than any other point.
Once it gets past that initial resistance, with the engine cold, the arm flicks back to the "choke on" position straight away. So it does sound
like a problem with the shaft catching the carb body or similar at that point.
If I get home early enough I'll take the air filter off and have a look for chafe marks tonight.
Brett Nicholson
Melbourne, Victoria
1974 VW Superbug L - Olive
1971 Morris Mini Moke - Mopoke
1966 Austin Mini - Audrey
1965 Morris Mini Traveller - Trixie
2007 Land Rover Freelander 2
2009 Nissan Pathfinder |
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Joel
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| posted on May 17th, 2011 at 03:16 PM |
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Mine had that exact same problem when I first bought it.
As ratty said with mine it was also the brass bushing that the choke shaft runs through the guts of and the fast idle cam rides on the outside of.
A very slight bend in the choke shaft was making it bind inside the bushing once the bushing itself rotated to a specific spot.
I could position the bushing in a spot where everything was all good and it would be fine for a while but after a few weeks it would spin back to the
spot and the choke would jam open again.
Bushings from other carbs did the same thing so I ran a drill the slightest smidgen bigger than the existing hole through the bushing and opened it up
slightly.
Not an ideal fix but it worked.
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psimitar
Son of Jim - Creator of Good
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| posted on May 17th, 2011 at 11:42 PM |
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Or the shaft could be all carboned up like on mine. The oil you keep putting there dries up and turns to a carbon residue along with years of what
it's been sucking in.
Take the top of the carb off and dismantle including the plate from the shaft and shaft itself. Use carb cleaner to clean the shaft and bearings and
to see if the choke is work just connect to a 12v source and ground the casing and you'll see the element curl up. If it don't then it's dead.
Once clean and the auto choke not installed you should have a lovely free choke shaft that returns by the choke weight
madness is in the eye of the beholder  |
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bnicho
A.k.a.: Brett Nicholson
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| posted on May 23rd, 2011 at 12:40 PM |
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Hi,
I pulled the top off the carbie on Saturday. It wasn't gummed up and the float bowl was clean, which is nice!
I removed the fast idle lever grubbins and the bronze bush. There was some grot in the bronze bush, so I cleaned that out, greased it and
reinstalled. I also removed the element, plastic cap and greased that side as well. It still was a bit sticky, so I removed the bush again and gave
it a very lght file with a fine chainsaw file. Then I reinstalled and the stickyness was gone. So it all went back on the car and the choke was
resent to the old mark. Everythng seemed to be working fine.
This morning I went to drive the car and it wouldn't start! The choke was definitely free and it had rotated. It just wasnt't rotating to the
"full choke on" position, even though it was around 10 degrees C.
I set it manually to full choke and it fired right up. Within a couple of kays it was idling normall - choke off.
I will try resetting the choke to "more" tonight.
Do these choke elements lose their springiness over time? It seems like mine has. It's defintely hooked on correctly and can be operated by hand to
to the full choke position with very little pressure.
Brett Nicholson
Melbourne, Victoria
1974 VW Superbug L - Olive
1971 Morris Mini Moke - Mopoke
1966 Austin Mini - Audrey
1965 Morris Mini Traveller - Trixie
2007 Land Rover Freelander 2
2009 Nissan Pathfinder |
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ratty 63
A.k.a.: Rossco
Custom Title Time!
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| posted on May 23rd, 2011 at 01:01 PM |
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| Quote: | Originally
posted by bnicho
Do these choke elements lose their springiness over time? It seems like mine has. It's defintely hooked on correctly and can be operated by hand to
to the full choke position with very little pressure.
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I've only ever seen them stop working when the heater element fails. Then they usually either don't turn off, or don't do anything at all... but
yours is doing the opposite 
Are you sure that the choke cam is not binding on the outer lip of the bush? (ie: the nut holding it all together is too tight) If you are then I
would try resetting the choke to 'more' as you suggested and see if this works... If it is still eratic it might be time to try to find another carb
that you can swap parts from in order to elimate the problem.
R
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psimitar
Son of Jim - Creator of Good
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| posted on May 23rd, 2011 at 02:41 PM |
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Anything springy loses some springyness over time and this does heat and cool that work hardens it so a little tweaking may well be necessary.
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bnicho
A.k.a.: Brett Nicholson
Wolfsburg Wizard
Posts: 436
Threads: 55
Registered: February 24th, 2009
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Location: Melbourne, Australia
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| posted on May 23rd, 2011 at 08:53 PM |
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It won't matter for a week or two now anyway. I noticed the clutch slipping a little last week, so i checked the free play on the weekend. Tonight
it started slipping badly in 3rd and 4th at anything more than light throttle. Time for a new clutch and main seal while it's out.
Brett Nicholson
Melbourne, Victoria
1974 VW Superbug L - Olive
1971 Morris Mini Moke - Mopoke
1966 Austin Mini - Audrey
1965 Morris Mini Traveller - Trixie
2007 Land Rover Freelander 2
2009 Nissan Pathfinder |
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