Throttle butterfly stop

[andyy]

Hi folks

Whilst investigating a misfire on my Griff 500 I noticed that the throttle butterfly stop on the plenum was so loose that it had screwed itself all the way in.
Does anyone know how far out the butterfly stop should be ??
I thought that the butterfly should always remain slightly cracked open to stop the butterfly getting wedged stuck.
Any thoughts please

Thanks Andy

[spend]

small hex from the bottom moves the throttle close stop and the big hex on the top the idle air, bearing carrier on shaft near cable the throttle open stop ... seen a few spindles that needed replacing due to injudicious adjustments , bent, metal ground away...

I would recommend removing plenum and making sure the throttle moves nicely through 0-90degrees and the air passages etc are clean. If your throttle is adjusted to fully open, thats when you may need the double return spring mod

[andyy]

Its the small hex thats loose
If I unscrew it, it means that the butterfly is always slightly open so the idle speed is higher.
Just wondering if there is some sort of factory setting

[Mark Adams]

If you look into the throttle housing and operate the throttle, you will see that the top of the butterfly comes towards you as the bottom moves away.

The correct initial position is that the top of the butterfly should be 1mm nearer to you than the bottom. It is easiest to check this by sliding a 6" Engineer's Steel Rule in at the top and bottom to check the position. In case of emergency you can use a bit of welding rod as a depth gauge.

After the butterfly has been adjusted, it will be necessary to check the Throttle Position Sensor (TPS) voltage which should be 0.32-0.34 Volts.

This is actually something we routinely check, and it is not uncommon to find them over-centre. Of course that causes havoc with the maths in the ECU, since initial motion of the butterfly actually reduces the airflow instead of increasing it.

[andyy]

Brilliant as ever Mark
Thanks very much
Andy