4A tickover revs changing.

[dpb]

Hello

 

On starting my car ticks over at about 800rpm.   After its been running for about 20 minutes or so,   the tickover revs whilst at traffic lights etc has gone up to about 1200 to 1300.  For full disclosure,   I attempted balancing the carbs a week or so ago,.    I adjusted the throttle screws to balance the air input and adjusted the mixture to stop changes when lifting the piston (as is says in the wsm).  I succeeded in getting the plugs to  be a nice toast colour,   after years of running too rich and being black and sooty

Anything in that process that could be causing the tickover variation?

 

Cheers

Dave

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[ctc77965o]

On starting means with choke? The choke levers also have some tickover adjustment....that would help you get it stabilised ?

[dpb]

Hi. No choke as its quite warm, and I checked the actual bits to see it was fully off. 

 

[RogerH]

Hi Dave,

I've also had this.  What I noticed at the time was that when the revs increased the carb linkage had not fully returned to its stop.

 little prod on the linkage at the tickover screw area brought the revs down.

Impossible to keep clean when running and lubricating the linkage increase the adhesion of muck/dust.

Make sure the linkage is not stiff etc etc.

 

Roger

[harlequin]

What carbs do you have dpb? The symptoms are what you could expect from a faulty Stromberg bypass valve but I assume your carbs are to early to have them.

G

[dpb]

HS6 carbs and the choke is all definitely off.

[harlequin]

First place that I would check is the linkage, things like the pedal hanging up on the carpet, split pin catching on somthing or if you have a cable a strand of frayed wire.

George 

[ctc77965o]

16 hours ago, dpb said:

HS6 carbs and the choke is all definitely off.

OK, so you are describing normal engine operation.  The engine starts below operating temperature, has higher friction losses due to oil viscosity, turns slower given the power generated by poorly atomised idle fuelling. Fast Idle on choke lever should be effective before jet movement starts... so you can use a 'little choke' to bump up the warm start revs until its proper hot.  Its not a defect, its a feature.