stuttering idle speed

[yorkylancs]

Its hard to explain but sometimes when its idling the revs drop quickly from 1400 revs to about 800,its on the verge of stalling,which it was doing until i turned the idle up.Also pulling away it needs a lot of revs to stop that feeling that it might cut out. Balanced the carbs the other day,and put a new air filter in it,ever since i have got the exhausts sealing properly,it seems worse.It has been laid up for a while,and the problem wasnt there last year,seems worse the warmer it gets,any thoughts?

[Phil-VTwin]

Could be a mixture problem, what colour are your plugs?

[yorkylancs]

brownish white,not really any different to normal,its ok once the revs are up..

[warby221]

If you need a lot of revs to set off it sound more like an air leak on the engine side of the carbs to me especially with the erratic tick over
Check your vacuum pipes over and make sure there are no leaks from them
Check the state of the rubber mounts for the carbs to make sure there’s no leaks around the joints to the engine and the cabs

[sirch345]

If you need a lot of revs to set off it sound more like an air leak on the engine side of the carbs to me especially with the erratic tick over
Check your vacuum pipes over and make sure there are no leaks from them
Check the state of the rubber mounts for the carbs to make sure there’s no leaks around the joints to the engine and the cabs

Yorky,
I'm inclined to think the same as Warby, that your bike has an air leak somewhere on the intake side.
Also check the take off points from the inlet manifolds (the ones you use for balancing the carbs) are air tight and that all the breather pipes are properly connected to the air box, especially that one underneath the a/box up at the front (clutch lever side).

Chris.

PS. Did you fit a new standard air filter

[yorkylancs]

Can anyone tell me what the pilot screws should be set at.The rear on mine is 3 and 3/4,and the front is just a 1/4,this doesnt look right to me,even allowing for the rear running a bit richer,cos it runs hotter.Has anyone got any settings(Turns out from fully seated)Thanks

[tony.mon]

Someone will be along in a minute with the correct settings, just had a look in the Haynes but couldn't find it.

But 1/4 out seems definitely wrong, unless you have some very unusual parts fitted, IMHO.

Try setting the rear one at 3 1/4- 3 1/2 turns out and see what you get in the way of engine response.

This just makes it richer, so you shouldn't do any damage, worst that will happen if it turns out (no pun intended) that 1/4 out is correct for your bike is that you'll get the plug sooted up and will have to take it out and clean it.

Gotta be worth a try to see if it sorts your problem?

If it's much better after adjusting, then you'll need to get it set up properly.
And re-balance!

[yorkylancs]

Been down to my local dealers,he says it should be 1 turn on the front,and 1.25 on the rear,that makes mine a mile off,however this is for a 2000 model mine is 1998,he said that they are probably the same though,the original problem was how it dropped suddenly from 1300 revs down to 800,then back up again just as quick,this is at stand still i havent even been riding it,could it be electrical?

[Jonesey]

This sounds like what they call 'hunting' Probably missed it cos my eyes have just opened, did you say your carbs are balanced?

[Jonesey]

Yep, they're balanced.

[Jonesey]

I've got 2 sets of carbs,(which I'll happily take bits off) and 2x new inlet rubbers if these are the problem, don't hesitate to PM.

[yorkylancs]

Still searching for a cure,they are balanced,maybe i should just live with it,seems to have happened since i got the exhaust to seal properly,last year it was spot on.Dont want to spend any brass on it if i can sort it myself,but might come to that.Seems looking through various old threads that they are a bit temperemental at low revs,but how bad is bad!

[Jonesey]

Yep, the 'cure' seems to be to turn the tickover up a tad, like the old saying goes, "they all do that mate"

[yorkylancs]

Jonesey,will be in touch if i need owt,cheers anyway might live with it for a bit,but will re balance the carbs with some decent gauges,rather than the poo i have at the moment,still thinking if its electrical though.Cheers.

[sirch345]

Been down to my local dealers,he says it should be 1 turn on the front,and 1.25 on the rear,that makes mine a mile off,however this is for a 2000 model mine is 1998,he said that they are probably the same though,the original problem was how it dropped suddenly from 1300 revs down to 800,then back up again just as quick,this is at stand still i havent even been riding it,could it be electrical?

Y/L,
My bike is a 1999 model. The carb jets are standard and I run the bike with Scorpion race cans (no baffles). The settings you have (

The rear on mine is 3 and 3/4,and the front is just a 1/4,)
to me sound rather strange, unless your carbs have been re-jetted IE dyno jet kit or similar fitted etc.

The air screws on my bike were front 1-1/2 turns out, rear was 1-1/8 turns out. Since fitting the race cans I have altered the setting slightly, but that should give you somewhere to start. I'm 99% sure those would have been the original settings.

My suggestion would be to try my settings, balance the carbs again and see what the bike runs like, keeping an eye on the plug colour.

Other than that you'll have to get it set up properly on a dyno.

As Tony say, this setting is quite important

Chris.