Want to increase the idle a bit.

[Captain Black]

So the ongoing pre TT fettle continues. I've sorted the slight slip in the clutch, and no matter how hard I try using all the torque its working fine. I've greased the throttle chain at the bars, and lined up the gears as they should be. Stuck some fresh 20/50 Motul in, and will do the gearbox and final drive this week. I'll check behind the rubber gators on the para lever just to make sure its dry. The valves sound fine so I'll maybe do them next time. My only concern is while the bike runs great , the idle is a bit low at about 900/950 rpm. Stuck my carbtune on and it looks a bit uneven , but of course I'm loathed to feck about incase I cock it up trying to chase 1100 rpm idle ideally.

I risked half a turn on both mixture screws but it doesn't seem to make much difference.
Is there a simple way to increase the idle without fecking everything up ?

 

[Smug]

Better to adjust the idle by using the throttle stop screws rather than the mixture screws.

 

[solidstate100]

As Smug says. Its what they are for! (on the topside of the carb, near the throttle cable)

 

[Captain Black]

Thanks chaps ill go for another run and twiddle them up tmrw. I'd better wind my mixture screws back to where they were 1/2 a turn.

Would the unevenness on my carbtune pro be caused by mixture or throttle stops settings .. They run a bit uneven at tick over and when I hold the throttle at 1500 /2000 rpm.

Needless to say its all a quick fiddle as I don't want to leave the old girl idling for more than a minute or so.

 

[Kenny]

Balance them purely on the throttle stop screws on top of carb. .

Ensure there is 2 - 3 mm of free play in the cables where they meet the carb otherwise as things heat up the tickover can climb to 2,000 rpm etc

 

[Captain Black]

Balance them purely on the throttle stop screws on top of carb. .

Ensure there is 2 - 3 mm of free play in the cables where they meet the carb otherwise as things heat up the tickover can climb to 2,000 rpm etc

Got ya thanks.

I'll screw my mixtures back, then go for a run. I'll take my carbtune pro and make my adjustments to the throttle stops at the local cafe while sipping a cappuccino in a calm manner, so I look like I know what I'm doing and the nice lady comes over to talk to me again .

 

[flatdog]

Captain, if you set up a desk fan or two these should supply adequate cooling airflow to let her run slightly longer

 

[DrFarkoff]

900 - 950 is about right if it's up to working temp

It's not an injected engine

A Flickering alternator light at tickover is a good indicator that you're about right rpm wise

 

[solidstate100]

Thanks chaps ill go for another run and twiddle them up tmrw. I'd better wind my mixture screws back to where they were 1/2 a turn.

Would the unevenness on my carbtune pro be caused by mixture or throttle stops settings .. They run a bit uneven at tick over and when I hold the throttle at 1500 /2000 rpm.

Needless to say its all a quick fiddle as I don't want to leave the old girl idling for more than a minute or so.

Your carbtune is measuring vacuum, not fuel/air ratio, so is influnced by the throttle stop screws, and also throttle cables when off idle. Best to go for a 10 min run first, then carry out the adjustments for the reason Kenny mentions above. BTW its quite normal for the airhead to idle slower when cold and not get to proper idle speed until its warmed up a fair bit.

 

[Captain Black]

Trouble is it sometimes dies from 900/950, I'm sure it would be happier at 100 rpm higher.

I've read 950 rpm then I've read 1100 rpm ...

 

[Captain Black]

Your carbtune is measuring vacuum, not fuel/air ratio, so is influnced by the throttle stop screws, and also throttle cables when off idle. Best to go for a 10 min run first, then carry out the adjustments for the reason Kenny mentions above. BTW its quite normal for the airhead to idle slower when cold and not get to proper idle speed until its warmed up a fair bit.

Thanks that's just made total sense. I'll play with the throttle stops with the carbtune linked up, I've get a fan somewhere as well.

I think it just needs a tiny tweak.

 

[Kenny]

You don't need a fan....only takes a few minutes. You'll find the throttle stop screw won't need turning more than 5 minutes on a clock face...very sensitive ( like me ). Have that run to warm her up, then do it at home as said above when the ignition light is flickering ( about 1,000 rpm ) The older heavy flywheel would tickover at 800 rpm ! The mixture screws you mention, they only affect approx first 30% of throttle then the venturi fully takes over ( if you have bollixed them up, usually start and remain about 1-1/2 turns out from lightly closed.)

 

[Captain Black]

You don't need a fan....only takes a few minutes. You'll find the throttle stop screw won't need turning more than 5 minutes on a clock face...very sensitive ( like me ). Have that run to warm her up, then do it at home as said above when the ignition light is flickering ( about 1,000 rpm ) The older heavy flywheel would tickover at 800 rpm ! The mixture screws you mention, they only affect approx first 30% of throttle then the venturi fully takes over ( if you have bollixed them up, usually start and remain about 1-1/2 turns out from lightly closed.)

Kenny.... I'm on it in my mind now! In fact I think I'm an expert on carbs now.

I'm just backing off the mixtures to where they were , then I'm going for the balance, I'll probably use 1 minute increments as I'm a perfectionist .


PS the fan is to keep me cool while I work, it was really hot here today!

Thanks for the tips, I'll post tomorrow to let you know how amazing my carb set up skills are.

Edit; I may even slip some paper between the stops so they release at the same time...

 

[DrFarkoff]

You are REALLY overcomplicating this!

900 to 950 is correct

1100 is Too High and is for 1100 1150 bikes

If you have it at 1100 and you are in traffic the engine will get hot very quickly ! (And it will rev even more)

Set the mixture screws where the manual says they should be for the particular carb model i.e. 3/4 turn out from closed

and then set the balance (and tickover speed) at tickover with the throttle stops

Then set the balance on the cables so they open the butterflies at the same time

It is VERY important that you go for a half decent run to get the motor up to working temperature before you start doing these settings

If you don't it will all be screwed up and the bike will have a racing tickover when hot later

 

[Captain Black]

You are REALLY overcomplicating this!

900 to 950 is correct

1100 is Too High and is for 1100 1150 bikes

If you have it at 1100 and you are in traffic the engine will get hot very quickly ! (And it will rev even more)

Set the mixture screws where the manual says they should be for the particular carb model i.e. 3/4 turn out from closed

and then set the balance (and tickover speed) at tickover with the throttle stops

Then set the balance on the cables so they open the butterflies at the same time

It is VERY important that you go for a half decent run to get the motor up to working temperature

If you don;t it will all be screwed up and the bike will have a racing tickover

Ok thanks I'll do that , I tend to give it a good twenty miles at least as a warm up, it was just that it died at the lights sometimes and felt very laboured at 9/950 rpm, I got to thinking a tweak to 1000 rpm just incase the rev counter is not that accurate.,

I'll give it a ho tmrw morning after breakfast.

Thanks for the advice.

 

[B Murr]

Got ya thanks.

I'll screw my mixtures back, then go for a run. I'll take my carbtune pro and make my adjustments to the throttle stops at the local cafe while sipping a cappuccino in a calm manner, so I look like I know what I'm doing and the nice lady comes over to talk to me again .

Captain, if you set up a desk fan or two these should supply adequate cooling airflow to let her run slightly longer

You're assuming the nice lady at the cafe is a bit past it and lacking stamina and prone to overheating, she may be fitter than you think and as cool as a breeze.

 

[Captain Black]

You're assuming the nice lady at the cafe is a bit past it and lacking stamina and prone to overheating, she may be fitter than you think and as cool as a breeze.

She's really rather nice ...

But thinks the bikes I ride are odd..

 

[DrFarkoff]

Not being cheeky but if you learn to "listen" to your airhead you don't need gauges

Did she stall within a mile or so of a cold start?

i.e before she was warmed up?

In which instance it's a case of "They all do that Sir!"

 

[airhead_eire]

It is VERY important that you go for a half decent run to get the motor up to working temperature before you start doing these settings

If you don't it will all be screwed up and the bike will have a racing tickover when hot later

I'll second that. I find it usually takes 10+ miles to get the motor up to proper temperature.

 

[Captain Black]

Not being cheeky but if you learn to "listen" to your airhead you don't need gauges

Did she stall within a mile or so of a cold start?

i.e before she was warmed up?

In which instance it's a case of "They all do that Sir!"

No after a good run of plus 15 miles or more.

The funny thing is the bike runs at 9/950 rpm very steady and very quickly after setting off. Certainly within a mile or maybe even less. I thought maybe the rev counter was slightly out.,
I'll be getting up soon having a little breakfast then I'll take her out for a run and a twiddle.

If I can get her to sit at 1000 rpm and get those bars on my cam tune level at tick over and say 1500/2000 rpm I think that'll do it. I honestly don't think its that far out .