Setting the idle when it won't... idle

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Nortorious

Nortorious

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Hey everyone, I hope you are surviving the tail end of another good year if you like to be in the garage..

I had my carbs and idle dialed in pretty well a few months ago. We had a bit of good weather yesterday so I fired up my 850 Commando with dual Amals this past weekend to give it some winter riding to stay in shape. After lots of kicking I got it fired up and held the throttle to warm it up. It wouldn't idle without some help which is normal. But here's where I hit a challenge. On a 55 degree day it wouldn't idle even after getting warmed up. I couldn't adjust the idle screws in either direction, on either carb, to get it to just idle so I could increase or decrease it. So how do you get to the correct idle when the bike just dies without throttle? How do I get to a good starting place to adjust the idle?

Carbs have been recently cleaned and the air is 1.5 turns open.

Thanks!
 
Once you have proven both carbs are in “perfect” working order , check manual for starting point , I used Mikuni but do think carbs are all basically same , so have at it and good luck! …. Also check plugs and air filter before wearing out your leg , you could invite friend over for a beer …
 
Thanks gents! I blanked on the battery. Good chance that's involved. I'll hit the manual if that doesn't do the trick. Bushman's carb guide had some basics but not much detail.

Thanks!
 
You say you can't get idling with adjusting idle screws. Do you mean air screws or throttle stop screws?
I prefer the extended stop screws that can be adjusted with gloves on.
On the Vincent and the 16H, I always have to adjust the throttle stop screws to get cold idling, as they have a rear stand so I can't get them off the stand with a hand on the throttle. On some of my bikes I never have an idle . Prefer them to die when I crash.
 
Mike40M said:
You say you can't get idling with adjusting idle screws. Do you mean air screws or throttle stop screws?
I prefer the extended stop screws that can be adjusted with gloves on.
On the Vincent and the 16H, I always have to adjust the throttle stop screws to get cold idling, as they have a rear stand so I can't get them off the stand with a hand on the throttle. On some of my bikes I never have an idle . Prefer them to die when I crash.
Click to expand...
He says the air screws are 1.5 turns out, so he should be talking throttle stops.

Air (or mixture )screw setting at 1.5 is always a good start point and since I also have bikes that are allowed to die when the throttle is closed many of mine never get set anywhere else.

But, it isn't always the right setting for your motor and it interacts with the idle circuit.

Cleaning the carbs has changed something. Somehow you need to get the bike at a fast idle using cable or throttle stop screws. Then set the air screws to where it runs best, then set the idle you want, not before.

If it won't, suspect that when you rebuilt and refitted the carbs you may have gotten something wrong.

Did you fit new O rings to the air screws?

Float height, maybe?

Or air leak on the manifold, suspect O rings or overtightening of the carb flanges.

(Yes, I know air leaks most often show as high idle speed)
 
Madass gantry for Amals or a 33mm Kiehin CRS carbonator kit from Jim Schmidt and enjoy your motorcycle.

If it ran fine a few months ago... maybe fuel turned to poop, or a crimp on connector spade or bullet has an iffy connection that does not play well with a battery that was sitting for a few months. EI is supposed to work with voltage as low as 8V, but I doubt it works very well below the RPM tickle threshold for the reg/rect.

Anyway, I don't know what I'm talking about. This is my typing therapy session.
 
"a few months ago" is that ethanol or non ethanol gas in the tank? i would clean pilot jets first
 
alan hodge said:
"a few months ago" is that ethanol or non ethanol gas in the tank? i would clean pilot jets first
Click to expand...
Non ethanol. I'll take another swing at it later this week and update the thread with more findings.

You guys like movies about gladiators?
 
baz said:
Keep those pilot jets as clean as possible
Click to expand...
Bushmans carb page is pretty good.
You say you recently cleaned the carbs, but did you check them by blowing air a, into the pilot bellmouth hole, b, ditto when the float bowl removed?
Both times either blocking with finger on the three pilot holes?
 
Was a “ball hockey” ( full contact ice hockey team rules played in ice-less rink) in local summer league “Gladheatehers” … they even had game shirts , I never played for them , but lots of laughes when those guys were playing , what an outfit they were …
 
Shame, shame, shame on me.. it was the @&#$ battery. Haha. I'm getting old and thoughtless rather than old and wise.

Thanks for all the suggestions. I still do need to sync the throttle screws to get it dialed in, but at least now it idles nicely.
 
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