'70 cmdo idles just a bit slow when warm

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goo

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Oct 6, 2011
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sometimes it feels likes its gonna stall. maybe 900 rpm or a bit less..
can't i just tweak each screw about 1/4- 1'2 turn? or does it need to get more complex to maintain syncro?
'70 cmdo idles just a bit slow when warm

'70 cmdo idles just a bit slow when warm


late breaking news..this just in.
'70 cmdo idles just a bit slow when warm
 
The screws that are visible on the side of the carb are for idle mixture, NOT idle speed. The screws that face upwards at an 45% angle next to the ticklers are the idle speed adjustment. Don't adjust them by as much as 1/4 or more or your idle will be about 3,000 RPM. A very slight adjustment in a clockwise direction on both carbs will raise the idle without changing anything else.
 
Yes, those idle stop adjust screws are very sensitive, but make sure to turn them exactly the same each side. It may take a while to get it right. I've been dicking with mine all spring and I think I've got them about right now. It also depends on the EI if you have one, and the AAU can be a real problem if the springs are weak. I have to say mine's much better than it ever was, now with the Pazon, anodized slides and new jets. Sometimes I can even take the hand off the throttle. If there's too much slop in the slides, there will be a bit of droop in the idle coming off the bottom. Sometimes it helps to make the idle mix a bit richer, screw in the pilot screws a bit until it gets a bit lumpy, again equal on each side. Then you may have to mess with the stop screws again to get the idle speed back up. I don't like mine idling under 1K, and it will when it's hot, it'll go down to about 500 and it sounds like crap especially when it's not completely hot.

Dave
69S
 
Hey Goo ,Take a net to drag behind the Snorter to clean up all them firemen. Drag them over to the women's strip bar and dump them on stage. As for carbeuration ,the slides are shot.
 
Gooday Goo

I have worn out slides and a rock steady 700 idle. What made the difference for me was setting the float levels spot on, regularly cleaning the idle circuit and fitting the Trispark with idle stabilisation.

Follow the Bushmans setup by the book and you will understand how to set these screws.
 
To get a sense of how shot the slides are I greased my fluted worn old ones and got decent idle back for a while even with the AAU wanting to stick in advance. Once electrics stable and carbs close to spec I diddle idle equal by sound and feel of the exhaust puffs. Perfection can be done with vacuum gage or manometer tube. Idle is set once fully warm of course.

Idle rpm needs change a bit, 600-ish to show off the soft pets in crowds or 900-1000+ to keep oil flow and electron charging up between runs. Pilot jet zinc oxide crust clog is very famous ancient issue that needs a wire or tiny drill bit to clear or boil in vinegar or corrosive carb cleaner. Amal designed our carbs so 1.5 pilot turns out is best base line idle, which is mostly set by float level if nothing else wrong. But even with float level and pilot screws each off this ideal, perfect idle and off idle operation is still possible and common- ugh its the state my Combat has been in all spring, but so good I ain't messing with carbs for a while till something else makes me or just bored nothing else to work on. Get the thumb screw slide adjusters for a treat to diddle with each and every ride. If bores worn to fluted too, then might get anodized slides with one size smaller cut out to make up for it. Worked for my Combat about a year now. I'm putting Lucas oil treatment on AAU every so often in hopes it'll last a few years more.
 
Hey Goo, how old are your gaslines and manifold crossover line and float needles ? You'll need some firemen to put out the crossover gasline fire too.
 
800 rpm idle is pretty good , Id say . AS . . .

This tribe sets idle screws OUT , just one in to get slides dead even . At least out in the sticks or on a track .
This enhances engine brakeing , or you get more ' slow down ' closeing the throttle . Provided it picks up clean , off closed .

' We ' use the BRAIDED fuel line , laminated clear armour core rubbish . A bit less likely to get holed and go KABOOMB , and so on.
EVEN for the induction balance tube . AND OIL LINES . particularly. Please .
A longish removeable one on the return that you can throw over the side , on oil changes , Gets the whole kaboodle FLUSHED / PURGED .
As in ALL the old oil expunged . If you wait untill youre ejecting clean oil , running .Before reconecting and correcting tank level .

1100 was minimum engage point , Combat Cam , I think 800 , std cam . Where it'd pick up clean & not shudder / stall .
 
Torontonian said:
Hey Goo, how old are your gaslines and manifold crossover line and float needles ? You'll need some firemen to put out the crossover gasline fire too.


just got new fuel lines
 
goo said:
Torontonian said:
Hey Goo, how old are your gaslines and manifold crossover line and float needles ? You'll need some firemen to put out the crossover gasline fire too.


just got new fuel lines

1/4 turn, or much less, on each side may do the trick. Balance them with your ears. No big deal. Were just talking about slide resting here.
Here is the real issue. Low idle tells me your carbs are buttoned up nicely and is very controlable. High idle, on the other hand, is what everybody seem to cry about and requires much intervention.
Don' make a big deal of it because everybody else will do that for you.

An added thought, are your plugs looking darker than usual? Maybe a 1/8 to 1/4 turn out of the pilot screw might be in order also.
 
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