Starts without choke

[Knowledge]

Most of the time, my scooter starts without using the choke.

Does this mean that the carb is over-fuelling through some other route, which compensates for the lack of manual choke? If corrected, could things be better?

I am running a 40 idle jet on a 30mm VHSH.

[St George]

Could be that the choke is not shutting fully.

[Knowledge]

Thanks, but it is fully shut.

The scooter runs well, so it is not as if the engine is struggling to run with a deployed choke.

[MickYork]

Pilot too big ?
Any issues with hot starting ?

[Rich Oswald]

I find that using choke is seasonal to a small extent. I use choke far less in Summer than in colder weather.

[Knowledge]

Pilot too big ?
Any issues with hot starting ?

No

[Knowledge]

I find that using choke is seasonal to a small extent. I use choke far less in Summer than in colder weather.

Acknowledged. Perhaps I have just outted myself as a fair-weather rider.

[Raveydavey]

Mtech on mine has a mental curve so have the stator set to something like 25deg at tdc. I find I rarely need a choke.

[Storkfoot]

It’s petrol vapour that ignites. When the engine is cold, the petrol is nearly all liquid. You then need more petrol in the mix to get the % of petrol vapour needed to cause ignition. That’s why we turn the choke off as soon as it is slightly warm.

If you can almost always start without the choke, your mixture screw and/or pilot jet is providing too much fuel.

That’s what I have always believed.

[Knowledge]

Thanks Paul. With a pilot jet of just 40, perhaps I will have a play with the mixture screw. At least I can do that without taking the carb apart.

Once the rain has stopped.....

[MickYork]

Maybe a lot of scooters would start without the choke ?

I'd leave everything as is, if it's running ok.

[Hat]

Depends how often I’m running mine. Anything up to 48 hours after my last ride i find it will start without choke. Anything longer needs it. Maybe there’s residual vapour in the carb or barrel that slowly leaches out?

[ROClarke]

Depends how often I’m running mine. Anything up to 48 hours after my last ride i find it will start without choke. Anything longer needs it. Maybe there’s residual vapour in the carb or barrel that slowly leaches out?

We just like to fiddle with them don't we.
Don't forget you are not running the original carb and running parts the scoot was designed for as well.