"Hunt on idle"

[Phil C]

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]

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]

Had this happen with all the crappy C15's I've had. Not anymore with the B31.

[Phil C]

Just out of interest, what's the usual cause? A bit of muck in the carburettor?

[idie]

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]

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]

 

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

[Mike Farmer]

 

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

[B44R Victor]

Suggest you look in a BSA manual, they explain what hunting is.  It's an incorrect tick-over mixture screw setting.

[Beesy]

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]

"Hunt" seems an odd word to describe uneven running. Anyway, I now have an idea of what it means. Thanks.  Phil

[MGI]

Hunting for petrol presumably...

[hoogerbooger]

Found this old thread. My B40 is " hunting" big time on idle after some tinkering......

Float height too high a poss cause ? Too rich?

.....I'd just reset the concentric carb float height because the tickler wasn't flooding the bowl and it wouldn't start after a carb strip down and clean. Now it starts OK ish but on the previous carb idle  settings is noticeably higher in revs, but hunts up and down big time.

My first guess was an air leak....but it's not at the carb manifold flange....and exhaust not obvious blowing( just put it back on). Since the previous time I started it I've also reset valves, timing, and points.... but my head is thinking check float height again ?)

[Derek996]

"Hunt" seems an odd word to describe uneven running. Anyway, I now have an idea of what it means. Thanks.  Phil

I've always understood "hunting" to refer to a tick over where the engine speed would vary in a regular cycle

[iansoady]

It's like an old style diesel engine with a mechanical governor - such as a Series Land Rover.