Idle higher when warm ?

[James in Brum]

Hi gang,

My lovely bike seems all fine but once I have been riding for twenty minutes or so the engine does not slow as much as I would expect. It the isles at 3000.

I can drag it down with a little clutch off whilst the brake is on. Then it sits where it should

At about 1100.

Any ideas. Gang?

[husoi]

Is that for your zzr?

a bit more details before we can give you a diagnostic...

[James in Brum]

Yes zzr600

Not sure what Else to tell. It is definitely only once it has been running for 15-20 minutes. But once it starts that’s it.

[Guest]

I remember having something like that on a Z650 back in 78/79.

Long time ago......but I'm sure it was something to do with the throttle cable not fully shutting off.

[James in Brum]

My ignorant guessing would have been throttle cable but could not imagine how the using the bike for twenty minutes makes it happen.

Thanks for suggestion [mention]XTreme[/mention]

[Guest]

My ignorant guessing would have been throttle cable but could not imagine how the using the bike for twenty minutes makes it happen.

Thanks for suggestion @XTreme

 

[mention]fastbob[/mention] will know the answer I bet!

[Stu]

Possibly an air leak once it warms up

Something could be expanding and letting air in

[James in Brum]

Letting air in? At the. Carb?

[fastbob]

Stu beat me to it . I'm thinking an air leak too . Not exactly sure where but a good look around the carbs would be in order .

[Stu]

Its usually around the inlet rubbers!

A good way to check is to get it up to temp so the bike is at high idle then spray some WD40 or something around the inlet rubbers

[James in Brum]

Thanks gang. Will try to look this weekend.

[Mississippi Bullfrog]

If you can slow the idle down by dragging the clutch and then it idles where it should then I don't think it's an air leak. If it was the idle would go straight back up as soon as you released the clutch.

My guess is a sticky linkage or cable. If a throttle cable is expanding as it gets hot that might cause that effect.

[fastbob]

If you can slow the idle down by dragging the clutch and then it idles where it should then I don't think it's an air leak. If it was the idle would go straight back up as soon as you released the clutch.

My guess is a sticky linkage or cable. If a throttle cable is expanding as it gets hot that might cause that effect.

 

Carbs can do funny things especially CV ones .

[James in Brum]

Thanks all, it makes sense to think Carbs because they have been recently ish messed about with. Will try to wd40 see if it bubbles trick. If the weather is dry this weekend.

[Mississippi Bullfrog]

Thanks all, it makes sense to think Carbs because they have been recently ish messed about with. Will try to wd40 see if it bubbles trick. If the weather is dry this weekend.

 

It's not that it bubbles. WD40 is combustible so any air leak will draw it in and you'll hear the idle rise momentarily. You can use EasiStart as an alternative.

Or spray water and listen for the idle dropping slightly.

[Stu]

it makes sense to think Carbs because they have been recently ish messed about with.

 

In what way have they been messed about with?

incorrect carb settings can also make the revs hang high momentarily but it normally comes back down after a few seconds or so