Hyperactive throttle.

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Boomlander
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Hyperactive throttle.

Post by Boomlander »

Hi all,
The car used to idle very slowly and frequently stalled when the clutch pedal was pressed.
Since it's clutch refit the throttle response to the lightest touch on the accelerator is instant and I can't slow down the idle speed with the carb adjustment screw.
Also the exhaust is black with heavy soot and I'm wondering if the carb is the correct one for the engine. The identification tag shows AUD368 and the carb has a vacuum tube to the distributor.
Any advice greatly appreciated as always. ๐Ÿ˜
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kevin s
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Re: Hyperactive throttle.

Post by kevin s »

Is the return spring fitted correctly and tensioned at idle (weirdly it is supposed to go to a tag under one of the exhaust downpipe nuts).
Boomlander
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Re: Hyperactive throttle.

Post by Boomlander »

Oh heck!........ I never even looked at the return spring!
I will check it tomorrow morning, that would clearly explain why the throttle is so light and possibly the fast idle.
Many thanks for the reply. ๐Ÿ˜Š๐Ÿ‘

Boomlander
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Re: Hyperactive throttle.

Post by Boomlander »

The spring is in position but all the levers and adjustment screws seem to be a bit loose and imprecise. I've adjusted the jet nut upwards by two flats to see if it improves the mixture but I may eventually buy a reconditioned unit as I don't have any clue as to the condition of the present carburettor.

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mobylette
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Re: Hyperactive throttle.

Post by mobylette »

Have you checked there is oil in the dashpot?
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mogbob
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Re: Hyperactive throttle.

Post by mogbob »

Your AUD368 carb should be on a Austin Morris 1100 1971-1974. Morris Minors late should be AUD13.Both are A series engines so I wouldn't change it ,
unless the cash is really burning a hole in your pocket.
Follow the guy's advice.Tighten up what is loose , check out the return spring and oil in the dash pot and persevere with the mixture adjustment , it is running rich.
Follow the instructions in the manual for carb tuning or search Youtube.
Bob
JOWETTJAVELIN
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Re: Hyperactive throttle.

Post by JOWETTJAVELIN »

Throttle spindle could be worn allowing air in, which would cause the engine to race. As this part is brass it can wear, you can test by trying to rock it, should be a snug fit in the bushes.
jagnut66
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Re: Hyperactive throttle.

Post by jagnut66 »

I had a similar problem with a couple of my carbs, they would not adjust / allow me to slow the engine down. In the end I sourced a refurbished carb and reset it all starting from the beginning, as it were.
So I'd go with the above post which suggests that your carb parts may be worn.
See if you can get hold of a comprehensive refurb kit (may be a cheaper option for you) and replace the lot, then go through the adjustment process again.
Don't forget to double check the timing as well. A small twist of the distributor in one direction or the other can cause the engine to speed up or slow down, as required.
Not trying to teach you to suck eggs but sometimes we can get so bogged down with a problem we can overlook something.
Good luck and best wishes,
Mike.
1954 Series 2: 4 door: "Sally" -- Back on the ground with (slave) wheels and waiting to be resprayed......
1970 Triumph Herald 1200: "Hetty" -- Driven back from Llangollen in Wales (twice.....)
Boomlander
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Re: Hyperactive throttle.

Post by Boomlander »

Thanks for all the replies folks.
I will check everything that's been mentioned and let you know the outcome.
By the way, what effect would low dashpot oil have on the performance?
Thanks again for your help, much appreciated. ๐Ÿ‘๐Ÿ˜

myoldjalopy
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Re: Hyperactive throttle.

Post by myoldjalopy »

Likely poor acceleration and hesitation on opening the throttle. If there is very little oil it may well stall on trying to accelerate....
Boomlander
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Re: Hyperactive throttle.

Post by Boomlander »

Understood, many thanks. ๐Ÿ‘

mowogg
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Re: Hyperactive throttle.

Post by mowogg »

Screw not adjusting the throttle speed- this will probably mean the cable needs adjusting. THe cable legnth is too short as secured. It might be that the outer is not seated properly
Boomlander
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Re: Hyperactive throttle.

Post by Boomlander »

Another point to check.
Much obliged for the suggestion. ๐Ÿ‘

Boomlander
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Re: Hyperactive throttle.

Post by Boomlander »

Adjusted the jet jut upwards by a couple of flats and there is a noticeable improvement in the running. The idling speed has slowed but with the choke control fully in the engine struggles to keep going so I will be resetting the control cables and performing a full set up as per the manual.
P.S. What a useful tool the little jet adjusting spanner is! :D

Boomlander
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Re: Hyperactive throttle.

Post by Boomlander »

mowogg wrote: โ†‘Sun Apr 17, 2022 9:50 am Screw not adjusting the throttle speed- this will probably mean the cable needs adjusting. THe cable legnth is too short as secured. It might be that the outer is not seated properly
Finally got around to close inspection of the carburettor and controls now I've retired!
Discovered that the accelerator cable was not returning fully and holding the throttle open when the engine should have been idling. A quick tweak and a bit more tension on the return spring and Willum's tick over dropped to around 800 rpm instead of1350! The carb itself is in fine condition and will receive a polish. Also fitted electronic distributor and stainless steel exhaust so the job list is diminishing fast!
๐Ÿ“ƒ๐Ÿ˜

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