Author Topic: "Hunt on idle"  (Read 307 times)

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Phil C

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"Hunt on idle"
« on: 30 July, 2020, 12:02:57 »
Morning all, Just in case you're bored (unlikely given the beautiful weather), I thought I'd ask you about something I read in my new "Real Classic" magazine last night. The writer was talking about a carburettor issue and said that the bike in question (not a BSA) "would just hunt on idle". What exactly does that mean? I've come across the term " hunting" before, but am not quite sure of the exact symptoms or cause(s). I think the main symptom is the engine speed racing a bit? Phil

idie

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Re: "Hunt on idle"
« Reply #1 on: 30 July, 2020, 13:54:39 »
It usually means that the tickover is not regular. It goes up and down as if it is fighting an air leak or a rich mixture.

B Murphy

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Re: "Hunt on idle"
« Reply #2 on: 30 July, 2020, 14:04:55 »
Had this happen with all the crappy C15's I've had. Not anymore with the B31.

Phil C

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Re: "Hunt on idle"
« Reply #3 on: 31 July, 2020, 10:52:16 »
Just out of interest, what's the usual cause? A bit of muck in the carburettor?

idie

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Re: "Hunt on idle"
« Reply #4 on: 31 July, 2020, 11:16:46 »
It can be due to a partially blocked pilot jet, wear on the throttle slide and carb body. Float needle not shutting off properly. Air leak on manifold.

Phil C

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Re: "Hunt on idle"
« Reply #5 on: 31 July, 2020, 12:42:04 »
Thanks, Idie. If I had a memory bank, I'd store that in it. As it is, I'll try to remember it, and know that I can refer back to this forum. Phil

Mike Farmer

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Re: "Hunt on idle"
« Reply #6 on: 31 July, 2020, 20:01:17 »
 :) :) :)

One of the simplest things that may cause this is a partially blocked vent in petrol cap.

Another,often missed is the automatic advance/retard system being lazy. As I dont have clue what sort of ignition unit you have this is just a very general point.

Mike 8) 8) 8)

Mike Farmer

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Re: "Hunt on idle"
« Reply #7 on: 01 August, 2020, 12:14:54 »
 :) :) :)

Lets go to the ridiculous. I always assume hunting to be associated with low revs--tick over.  So my question is --Does it  still hunt at a higher rev setting-- for instance 1/4 throttle plus????

Mike 8) 8) 8) 8)

B44RVictor

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Re: "Hunt on idle"
« Reply #8 on: 20 October, 2020, 16:00:30 »
Suggest you look in a BSA manual, they explain what hunting is.  It's an incorrect tick-over mixture screw setting.
B44RVictor

BEESY

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Re: "Hunt on idle"
« Reply #9 on: 20 October, 2020, 18:05:19 »
The manuals and Amal sheets says it's a symptom of a miscarriage adjusted pilot screw, but I'm not sure if anything else e.g general wear on the other parts can cause the same thing.

I spent a long time adjusting mine. Some days it's fine others it hunts a bit. Seems to be effected by atmospheric conditions too.


Phil C

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Re: "Hunt on idle"
« Reply #10 on: 20 October, 2020, 18:15:08 »
"Hunt" seems an odd word to describe uneven running. Anyway, I now have an idea of what it means. Thanks.  Phil

MGI

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Re: "Hunt on idle"
« Reply #11 on: 20 October, 2020, 18:53:48 »
Hunting for petrol presumably...