Idling @ 8000 rpm

[Katman]

On a CV carb, with it's throttle butterfly fully closed, manually lifting the slide won't increase the revs as the closed butterfly isn't allowing sufficient airflow. That cylinder will just run rich and bog down.

[jonbuoy]

On a slide carb the throttle is mechanically connected to the slide. There is no throttle butterfly.

On a CV carb the throttle is mechanically connected to the throttle butterflies.

I know! I have them on my car.

[MSTRS:Me]

On a CV carb, with it's throttle butterfly fully closed, manually lifting the slide won't increase the revs as the closed butterfly isn't allowing sufficient airflow. That cylinder will just run rich and bog down.

Hence 'our' supposition that there is something interfering with the butterflies...
An airleak or lack of spring holding slide/s down just isn't going to cause the engine to race.

[cbfb]

OK so what I'm gonna do, I'm gonna get me a nice shiny new hose clamp so we can rule that out. Then I'm gonna give the carb insides a quick check. Then I'm gonna bung the carbs back on and without the airbox on, try and turn it over to see where the butterflies and slides are sitting. Hopefully that will tell us something.

[ducatilover]

On a CV carb, with it's throttle butterfly fully closed, manually lifting the slide won't increase the revs as the closed butterfly isn't allowing sufficient airflow. That cylinder will just run rich and bog down.

This is very true.


CBFB, if it's not sorted I can drop in on Saturday? Maybe sooner if need be.
I really doubt it's an air leak after the butterflies, I would assume it's an issue with the butterflies, have you set their clearance according to fact. specs?
The slides will only affect it, if the butterflies are open, the lifting slides will just lift the needles, opening the main jet, hence the rich running.
Also may be worth a peek at the plugs, but, I imagine you will find them as white as hell, indicating being lean.

[cbfb]

This is very true.


CBFB, if it's not sorted I can drop in on Saturday? Maybe sooner if need be.
I really doubt it's an air leak after the butterflies, I would assume it's an issue with the butterflies, have you set their clearance according to fact. specs?
The slides will only affect it, if the butterflies are open, the lifting slides will just lift the needles, opening the main jet, hence the rich running.
Also may be worth a peek at the plugs, but, I imagine you will find them as white as hell, indicating being lean.

Mate that would be awesome if you could. Will see how I go with her tonight and if still no joy I'll be in touch.

Good news is Manawatu Motorcycles had a used hose clamp (exact match of existing ones). Bloody good wee shop that, they break bikes, didn't know they were there till now.

I didn't touch the flutterbys when I took the carbs apart so I assumed they would be OK having not been changed? The service manual says this:

Attachment 229123

But wtf is the 'foremost bypass'? How do I set the clearance otherwise?

Plugs are brand new and have about 10 secs of running time on them.

[ducatilover]

Mate that would be awesome if you could. Will see how I go with her tonight and if still no joy I'll be in touch.

Good news is Manawatu Motorcycles had a used hose clamp (exact match of existing ones). Bloody good wee shop that, they break bikes, didn't know they were there till now.

I didn't touch the flutterbys when I took the carbs apart so I assumed they would be OK having not been changed? The service manual says this:

Attachment 229123

But wtf is the 'foremost bypass'? How do I set the clearance otherwise?

Plugs are brand new and have about 10 secs of running time on them.

Something may be interfering with the flutterbies...but wel shall see.
The foremost bypass may be the idle circuit, or the flutterby air gaps. I haven't played with CV carbs for a while, but, they are piss easy to figure out.
That attachment isn't working dude

[cbfb]

Something may be interfering with the flutterbies...but wel shall see.
The foremost bypass may be the idle circuit, or the flutterby air gaps. I haven't played with CV carbs for a while, but, they are piss easy to figure out.
That attachment isn't working dude

Don't think it's the idle circuit intake ports (assuming that's what you mean) cause they're a bit further forward.

Try it now:

[ducatilover]

Don't think it's the idle circuit intake ports (assuming that's what you mean) cause they're a bit further forward.

Try it now:

Is there a small bypass groove where (8) is positioned on the diagram?

[cbfb]

Is there a small bypass groove where (8) is positioned on the diagram?

Hmmm not sure from memory. You reckon that's a factor?

[ducatilover]

Hmmm not sure from memory. You reckon that's a factor?

Could be. It may help to check, but, I doubt a bypass port is enough to make it sit at 8000rpm.

[cbfb]

Could be. It may help to check, but, I doubt a bypass port is enough to make it sit at 8000rpm.

Yeah that's what I can't figure, there's got to be a lot of air getting in there somehow

[ducatilover]

Yeah that's what I can't figure, there's got to be a lot of air getting in there somehow

It's really all pointing to interference with the flutterbies.

[cbfb]

It's really all pointing to interference with the flutterbies.

Roger that. Will report back my findings later on.

[Drew]

Airfilter stops dirt getting into the engine, nothing more. It will run better without an airfilter (if the mixture is adjusted), your engine won´t last long sucking in dirt and crap off the road.

Wasn't gonna call you on this, but I will cos your attitude bugs me.

Run a bike with CV carbs without a filter and it will idle fine, but run like a sack of shit when you are on the throttle. Because there is a delicate balance of spring tension versus air flow to be maintained in order for the slides to sit at correct levels for the engine speed.

Roger that. Will report back my findings later on.

When we spoke on the phone I could hear the butterflies slamming home when you shut the throttle I thought. Would be funny if that was infact a linkage hitting a hose clamp.