Racing carby

1 Attachment(s)

Attachment 157838 A bit hard to see on my carby , but yes the vacuum advance line screws in there .

Unstable idle speed.

Quote:

Originally Posted by Mustlust

Having bought a replacement carby late last year, and having the little landie scooting all over the farm, I have a new puzzlement to contend with for 2020. <br>
Sometimes at idle the engine revs really high, usually after driving for a bit. Sometimes a tap on the pedal will bring it down again, although this is working less often now. Even under the bonnet when I flick the throttle arm it may not decrease the revs, and sometimes it does. <br>
I am thinking that something in the carby is sticking. All the external levers and springs are fine with the issue apparently directly with the carby. I’ve probably driven 5 kms since putting it in and initially all way well. <br>
Could there be dirt interfering with the jet???

Mustlust,

Check your butterfly disc clamp screws. If they come loose, the butterfly disc can slide around in the spindle and stop the throttle from closing fully. Remove carbie, back the idle screw right off and close the throttle lever. There should be virually no light showing around the disc. If there is, make sure that the spindle nut at the throttle lever is tight, then loosen both disc clamping screws and centralise the disc while holding gentle closing pressure on the throttle lever. Use some loctite on the butterfly screws so they don't loosen again. Be careful with the Loctite, any runoff will lock up your butterfly spindle bushings.

Also check that your distributor centrifugal advance is not sticking, as this will cause high and erratic idling speed. Most advances don't get much attention and need to be checked and lubed every few years. Sometimes the springs get rusty or stretch and allow excessive advance. Turn the rotor against the spring pressure - it should be firm and snap back fully and smoothly with no play in the springs. Also, check your vacuum advance diaphragm for rupture or leakage as this can upset the mixture.
I hope this is of help. Good luck! - 5380

Quote:

Originally Posted by ramblingboy42

...and here I was hoping to read about someone racing their S1 and looking for an appropriate racing carby.....[bigwhistle][bigwhistle][bigwhistle][bigwhistle]

Ditto, I thought we were going have a brace of DCOE Webers hanging off the side of the head[emoji16][emoji23]

I have one of those carbies with the vacuum advance missing. Mine only runs with the cold start on though[bawl]

Regards,
Tote

It perhaps could be that the centrifugal advance is sticking .
If that happens the idle will stick up for a long period and maybe decline or maybe not.
I had this problem many years ago with a VW type 3 I had set up for off road.
Regards PhilipA