Idle - How low can ya go?

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Hobot

Hobot

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There are two extremes of optimal tuning, maxed out w/o blowing out its brains, and to get it barely beating and warm.

My '38 JD 'Poppin Johnny' magneto tractor idles at 240 rpm, Trixie Combat on points came to me with steady 400 rpm idle and my P!! was a happy puppy at 600 rpm, even throwing a wake of dry sand in Fla ruts chugging along in 4th no throttle. Lovely to the soul but wonder if this is bad practice d/t oil flow starvation. But then again the loads are light and nil heat loads with such low fuel burn, I wonder if its just a wash w/o even the wear of highway runs. I'd leave tractor running in back ground while I'd work on taking apart my first Combat. Its heat siphon cooled twin and only got hand comfort warm petting my dark soul.

I've measured idle temps, in dead air against wall on heated cement in direct summer sun 100'F air, CHT, EGT and oil tank, to see they are lowest they ever get and go significantly up at first hint of raised rpms rolling or not.

So only thing I can think of not to set idle to barely living for as long as I like is lubrication. What's the seasoned reasoned logic or experience to follow for lowest sustained idle rpm? Not concerned with normal road going/alternator charging idle above 700 in this post.
 
I'm just happy when the bike idles with the tach showing a beat below 1k! I know that in my yout I played with my idle until I got it down to 800 on the high side of the beat. That of course was with points and some good gas. Its funny sitting here thinking back to that, I can even smell my bike. I used to ride on hot summer days along the Willamette River, through the hop fields. As the sun would start to set low the cool air would be along the river and the smell of the hops in the air with the big rainbird sprinklers putting moisture in the air. Damn, now that I think about it I might have got 600 out of her!
 
Aw man, what a delicious tale, though I seem to get a bit more cooked bug juice in the fumes : ( I like it when guys pull up at rally and turn their idle down till my bladder wants to relax like and infant in diapers. The ring of Norton heads attract bats, if you go slow enough they respond to the rhythms and keep up.
 
Idling below about 1,000 RPM is inviting low oiling, and all the related issues. There is no need to drop tickover RPM below about 750 "if you simply MUST".
 
About 1000 rpm is the lowest speed that will maintain enough surface speed to provide a wedge of lubricant and prevent cam to lifter contact. Below that and the cam will wear rapidly. Jim
 
Yes Paul low idle oiling is my ponder here. On the surface it makes perfect sense and all my life I've been told idle is about hardest on engine short of over rev or lugging. Yet there's plenty of examples of slow idle and low rpm lugging engines that last a long time. Most diesels and also the old hit and miss engines plus old motorcycles that needed a hand pump or 3 - every dozen miles or so. Saying its risky just ain't the same as listing what parts may be getting starved or beaten up.

I think Ms Peel's oppositic engine may allow setting idle to under 400 just to listen and feel its soft thumps in background for my pleasure and world at large. I've been around enough hi performance stuff to know they tend to offend one's senses to stay running w/o load. I loved to idle Ms Peel away from a big bike gathering short shifting up gears as slow-easy as possible w/o lugging to 4th, leaving impression of quaint obsolete cycle, then as soon as out of sight shift to 2nd and send a surprise hi rpm Snorton roar like a dragster launch.

Head just needs a trickle of wetness and crank sling keeps oil moving through rods big ends, so I'm betting its a non issue till I learn otherwise. Main issue for Peel to idle down much is the Lake Inject w/o an idle circuit so may well be limited to over 1000 rpm 'idle'. ugh. But with programmable ignition may be able to over come that for the suspense between combustion.

[video]http://www.youtube.com/watch?v=hc3dGHXHiZA[/video]

[video]http://www.youtube.com/watch?v=eWMJ6IrJ348&NR=1[/video]

[video]http://www.youtube.com/watch?v=T3QfR0iPHAY[/video]
 
First it's how fast. Now it's how slow. Lowest Idle? Lowest first gear? What the freak is with you, man. :P
 
Loved the last clip with the hit & miss--. now I've got an old 1 1/2 fairbanks open crank hit & miss in the shed :idea: :idea:
Terry
 
Oh mY Mellow, that is music to my soul, never heard the slow idle played with string accompaniment before, delicious.

About 1000 rpm is the lowest speed that will maintain enough surface speed to provide a wedge of lubricant and prevent cam to lifter contact. Below that and the cam will wear rapidly. Jim
Click to expand...

Ugh, this is what I needed to be aware of, where the damage might be occurring.
Still now I know I'll just have to balance my destructive ways with motorcycles and my worldly pleasures to share. Its also another reason I want to increase oil flow on exhaust side to drain over cam lobes on slow idle.

As to my full range of extremes, fast as I can to slow as I can, Commando's are my ticket to heaven and hell - and my triple rod linked Peel must do it all really well or I'm quiting the hobby for something else that pays back in thrills and spills I can afford.
 
hobot said:
Oh mY Mellow, that is music to my soul, never heard the slow idle played with string accompaniment before, delicious.

About 1000 rpm is the lowest speed that will maintain enough surface speed to provide a wedge of lubricant and prevent cam to lifter contact. Below that and the cam will wear rapidly. Jim
Click to expand...

Ugh, this is what I needed to be aware of, where the damage might be occurring.
Still now I know I'll just have to balance my destructive ways with motorcycles and my worldly pleasures to share. Its also another reason I want to increase oil flow on exhaust side to drain over cam lobes on slow idle.

As to my full range of extremes, fast as I can to slow as I can, Commando's are my ticket to heaven and hell - and my triple rod linked Peel must do it all really well or I'm quiting the hobby for something else that pays back in thrills and spills I can afford.
Click to expand...

Dumping more oil on the cam would not help avoid metal to metal contact. More surface speed would be needed to create the hydrodynamic wedge. So you would need to make the camshaft larger in diameter, or use roller followers. Jim
 
I have never understood why one would want a "low" idle.

An idle defined as low seems to me to run the risk of both possibly killing the motor and also not keeping the oil flowing more nicely.

I suppose being stuck in traffic on a hot day one would not want the motor getting hot and so maybe a lower idle would be in order, but then the
oil would also not be pumping as fast.

I keep my idle around 1100-1200, right or wrong.
 
Dumping more oil on the cam would not help avoid metal to metal contact. More surface speed would be needed to create the hydrodynamic wedge. So you would need to make the camshaft larger in diameter, or use roller followers. Jim
Click to expand...

Ok makes such perfect sense damit. Alrighty they modify engines to stand racing, like drilling the cam to supply lobes, maybe that could allow some oil skidding to enjoy unnaturally slow idle? Could apply dry friction coat and renew now and then.

Ms Peel is pure experimental excess, Trixie is pure plain Jane factory Combat that gets treated as easy and normal as anyones. Hot rod road going sports bikes idle under 1000, so I want to go half as slow as well half again faster around them. Wouldn't you?

My dad told me to listen to a car's idle rather than its rev up sounds to better judge its used condition to deal on.

Peel has deep thumper sound at idle d/t the 1.5" one piece 2>1 with hollow Dunstall volume on end. It's irresistible rhythm I want petting me down in my diaphragm. Its all the more pure w/o the header ringing d/t the installation wrap to the Y. Makes the engine sounds more pure at front too which I like.
Most the front noise is the whole head ringing not its little parts tapping it.
The bats can't resist this hi freq. sound so Norton's sonic signature has broad appeal.

[video]http://www.youtube.com/watch?v=qBo3fNHy7Ig[/video]
 
Hobt ~ thats cheating as the Bulldog was a two stroke ! (??)

We had one on the farm when i was a kid ~ Even I could count the strokes as a toddler ~ 8) :lol:
 
Hey Stuart, i never knew about Bull Dog or their engine operation till someone posted this on another gear head list recently. Interesting imprinting you must have for slow engine performance. My first was a farmer uncle spinning flywheel on JD that coughed and POPPED and smoked and bleached before it got warmed and fuel switched. Other memory still amazing to me was Uncle Boots driving one hand with me and brother on the fenders, tricycle gear in soft sand ruts while rolling a cigarette with the other, lighting it with wood match, chug chug chug chug chug chugging. Love it so much better get a few cams as spares.
 
Hobot...
The MacDonald that my ol man had had to be primed with a fire box at the base of the drivers compartment before spinning it up with the fly wheel ~

I recall a nipper laying in bed at night listening the boom boom of the low idle as Dad worked through the night to get the paddocks/ fields ready for the annual wheat/ barley/ oats plant~ It could be heard for miles ~ we could count the revolutions !! :lol:

That particular tractor ended up in an agriculture museum.
 
Ahh the sounds and routines of a different world. I'm not imprinted as deep as you but enough i want slow deep thumps as much as i can in my dream machines. We have it so easy and glad of it for our work a day lives but simple slower pace is so delicious when there's time. I counted my '38 pulse and timed em on a watch, 240 rpm idle and guessimate ~1800-2000 WOT : )
 
Seems to me if your flywheel is heavy enough, you can slow it down as much as you like. That's why the JD, Farmall and others had those big external flywheels, plus you could run a belt off it. My diesel JD2020 certainly doesn't sound like those any more, but it still doesn't go much above 2500 at top speed as a 4 cylinder. It will certainly pull the hair off a gnats ass though.

Dave
69S
 
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