Idle needs a tweak..

King Rat

King Rat

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Throttle cables are tight, so I think I need to give the little brass screw a tweak, but I can't remember which way is which. It has been 15 years since I had a carb to fiddle with and much knowledge has ebbed since then. :blast

Can someone help me out please? I don't want to just turn and see what happens, because I haven't got a balancer system to fall back on. It is just going to be a 1/32th of a turn each side jobbie. Presumably to do it when the motor is warm too. :thumby:
 
Do it whilst the engine is idling and you'll hear the difference. You're only tweaking so you can tweak it back to where it was without any bother.
 
Not sure I’m clear on what you intend to adjust,however,
The throttle cables shouldn’t be tight.they should have @ 1/2 to 1mm free play
Once they have free play you can check/set mixture screws underneath the carbs .
Then set idle speed using the adjuster screws on the engine side of both carbs,
Unless you have a good “ear” this will be loads easier with vac gauges.
After that the cables need readjustment to balance the throttle take up.
In theory non of the above should be done without ensuring that,the valve clearance are correct,the timing is correctly adjusted and the spark plugs are good:thumby:
 
I DETEST play in my throttle cables. When I turn the throttle I want INSTANT take up, not a bit of movement before something happens. I know what the books say - I disagree with them because I simply don't like it. I adjust that play out, so the slack is about the width of a human hair once it has been pared down with a scalpel. :aidan

The rest - thank you!
 
King Rat, problem with that approach is that there is usually some change in cable length when you turn the bars, and some folk like to set the free play at the point where there is no change on full lock, which a Mikey says is around 1/2 to 1 mm.

The other problem with that line of thought is that it is the movement of the slide that makes things happen, but the throttle cable only goes to the butterfly, and there is no advantage in opening the butterfly a lot faster than the slide can move - you just get a over rich mixture which bogs the motor down.
Most of the time most people will have the throttle open past the idle position , so the play at idle makes no difference.

Personally I make a point in not ridding a motorcycle on public roads as if I am in a hurry to get anywhere.
I like to get the bike flowing smoothly between corners, not jumping on the brakes/ throttle every time there is a bend in the road, and from what I can see that is the style favored by most airhead riders, so again clearance is just not an issue for most - unless it is extreme like having the twist grip gear a tooth out.
 
Not exactly the crispest response to twisting the throttle from Bings! I could understand no slack in the cable if you’re riding a modern single with a pumper carb.

When the carbs are perfectly balance it does make a huge difference to the drivability and I doubt you could feel the play in the cables
 
I like the quick action throttle and high torque cam combo on my Airhead - Instant Grunt and then it runs out of puff around the time my skill does so it suits me :D
 
King Rat said:
I DETEST play in my throttle cables. When I turn the throttle I want INSTANT take up, not a bit of movement before something happens. I know what the books say - I disagree with them because I simply don't like it. I adjust that play out, so the slack is about the width of a human hair once it has been pared down with a scalpel. :aidan

The rest - thank you!
Click to expand...

As ever Simon,
You know best:blast
 
King Rat. Over your various posts on this site, you have admitted that you don't know much about airhead maintenance. You have asked a question to which people have given you the answer.

Mikeyboy and Steptoe do this for a living. Not sure about Beemerboff, and although he's a contrary git at times, one has to admit, he also knows his airhead onions.

By blatantly ignoring their advice after their respective years doing this, you're not going to get any help and will start to see this picture more and more.
 

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http://www.vintage-register.co.uk/library/Technical sundries/CV Carbs.pdf

Best carb information I have found on the net, just about the only one with details of the idle air system ( in the tuning section)

Attention to make certain the system is clear from the pilot air jet to the two pin pricks in the mixing chamber will ensure that the system is operating correctly and may even make a bigger difference to the way the bike picks up than adjusting the cable.

And also might help some to understand why rolling the throttle open smoothly works better than jerking it WFO.
My R75/7 has pilot air jets as shown, my R80 G/S PD dosn't, on both I am able to check and clear by blowing into the jet/ passageway with the needle on a pressure pack of carb cleaner.
Never seen it mentioned in any internet " learned " treatise on carb cleaning, but it can make a big difference!

FWIW my 1000cc R80 which came to me with no pilot air jets in the passageway picks up cleaner and faster than my 1000c R75/7 which has them, but the light flywheel and low gearing might have something to do with that too!
Lowering the gearing on the R75 to the same 37/11 as the G/S has made pick up a lot better than you would expect for the relatively small change in gear ratio, so might also suit those who prefer something with a better pick up than a stock R75.
 
Nippy Normans supply Touratech, Wunderlich, Desert Fox and many other makes of accessories.
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