Club 80-90 Forums

Hi all, Got a small problem. I can't get tick over any slower than 1375 rpm. the idle screw is slackened right off and throttle cable is not tight. The mechanism is fully returning.
Any thoughts kindly appreciated.

It's cold are you sure it's not just on choke which has a fast idle?

This pic shows the choke set ( flap is closed)
The fast idle cam (and choke) can be released by pressing down on it where my finger shows, the flap should open and there should no longer be fast idle.

Hi Itchy feet, It's when it's been running a while, In fact all the way from the new forest to suffolk.

Worth checking the fast idle is not stuck on by pressing that point.

Yeah I had done all that, just so puzzling that everything appears to be ok.

To over rev you need extra air and fuel, normally the chokes open and this draws in aire which passes jets and draws in fuel
so if the chokes are definetly both in their correct closed positions ( there is some adjustement) and you have an air leak below the chokes ( say the gaskets or a vac hose) it will cause the mixture to be weak but not increase the revs unless you also have an overfueling problem.
So perhaps two faults?

If the chokes are in the correct position , and not as ItchyFeet suggests being held slightly open either by bad adjustment or the cold start mechanism, then I would say its an air leak, usual suspects are the vacuum pipes , have you checked them ?

Does an air leak below the chokes increase the revs? Not sure it would unless it was rich anyway

If the timing has moved that will cause a different idle speed.
leaky accelerator pump.
faulty float height.
vacuum throttle partially open
crank breather faulty
But don't rule out that the butterfly spindle might have partially seized in the carb body

Yeh timing is a good call.
when i had a carb with a faulty gasket that over fueled I just got a smokey idle not extra revs

itchyfeet wrote:Yeh timing is a good call.
when i had a carb with a faulty gasket that over fueled I just got a smokey idle not extra revs

But like you say with a little air leak that would increase the idle.. even a weak mixture will raise the idle speed

itchyfeet wrote:Does an air leak below the chokes increase the revs? Not sure it would unless it was rich anyway

I rekon so, with a petrol car you control engine speed by restricting the air flow, with a diesel its all about restricting the fuel.

pionte wrote:

itchyfeet wrote:Does an air leak below the chokes increase the revs? Not sure it would unless it was rich anyway

I rekon so, with a petrol car you control engine speed by restricting the air flow, with a diesel its all about restricting the fuel.

Yes but with extra air normally comes extra fuel because the air is passing the jets and pulls it in, an air leak below the chokes won't pull in more fuel it will just run lean, will lean be enough to increase the revs that far? Maybe.

Thanks for all your input. Checked everything over and over again got pissed with it, removed carb put a different bottom half on now does all it should do. By the way it's a carbed 2.1 DJ.

Thanks again.