Revs won't die down.

[z1bman]

Common faults




Won’t shut down 1:
Slide height of 0.70mm is critical, to high and the engine is slow to shut down. Prove by removing the tick over screw. Should rev and shut down in the desired manner.


Won’t shut down 2:
Caused by a long spark particularly when using new spark plugs. The plug insulation has broken down and the spark plug voltage is jumping a greater distance to earth. Weak spark changes ignition and combustion characteristics.


Fuel overflow 1:
Assuming the height of the fuel is correct. The fuel tap causes the sporadic spurt out of the tube. Changing the fuel height will not cure the problem because the fuel seat needle within the carburettor regulates flow in use and is not an effective shut off valve.


Fuel overflow 2:
Assuming the height of the fuel is correct and the fuel tap is working effectively then the floats are sticking. Change the float pins and insert pipe smoker cleaners along the bore of the float.
Excessive gap between tickover screw and lifter lever:
One or more of the slides has bottomed out on the slide floor. Further adjustment turns the common rail lifter bar clockwise.Start again and reset.

[Pigford]

Common faults

Won’t shut down 1:
Slide height of 0.70mm is critical, to high and the engine is slow to shut down. Prove by removing the tick over screw. Should rev and shut down in the desired manner.

Perhaps I'm misinterpreting this. but:

Surely the 0.7mm is a nominal value used the statically set slide balance? If you set your carbs at 0.7mm slide height at idle, you cannot guarantee idle speed - thats why a vacuum guage is needed??? It's usual to use a drill bit or ball-bearing to set all slides to same height statically - often quoted as 0.7mm although anysize around this value is arbitory

[floydsz1]

To wet to go for a ride but had it running in the workshop. Nice tickover then when hot revs are slow to die down.
Wind tickover screw right out and it revs how it should but obviously no tickover now.

[njwmct]

Had a similar problem with my Mark II when I raised the needle to cure a mid range flat spot.
Raising the needle 1 notch cured the flat spot but the revs would hang in the same way as yours.
The solution was to raise the needle by half a groove only - you can do this with some tiny washers that are supplied by Allens Performance.

[floydsz1]

Had a little ride round yesterday in between the showers and with the tickover screw all the way out the revs died down how they should but obviously it would stall unless held by the throttle grip.
Now what ?