Vulcan Drifter Riders

DISCUSSIONS => Drifter 1500 only => Topic started by: Fab on April 14, 2025, 02:02:47 AM

Title: Question about the (fake) choke/fast idle knob on the 1500
Post by: Fab on April 14, 2025, 02:02:47 AM
Reading old posts on this forum, I realized that the choke knob on the 1500 is actually a fast idle control.

From the user manual:
QuotePull the choke knob all the way out if the engine is hard to start in cold weather or at high altitudes, and then return the chock knob all the way back when the engine is warmed up enough to idle without using the choke.

Does this mean that the fast idle control only works in cold weather or at high altitude, or should it raise the idle regardless of temperature and altitude? I ask because it is no longer cold here, and pulling the choke knob does not seem to change the idle at all on my 1500, either when the bike is cold or when it is warm.

Thank you.
Title: Re: Question about the (fake) choke/fast idle knob on the 1500
Post by: drifter-paul on April 14, 2025, 02:35:59 AM
I use the choke in winter (in Australia) .
Whenever I use it , it makes for a fast idle , unmistakably ! I push it in after a minute warm up - earlier can cause a stall or stutter .
Title: Re: Question about the (fake) choke/fast idle knob on the 1500
Post by: Fab on April 14, 2025, 03:04:27 AM
Thanks Paul,

QuoteI use the choke in winter (in Australia) .
Whenever I use it , it makes for a fast idle , unmistakably !

It's spring here in Italy, so I can't test it in cold whether at the moment.
If I understand correctly, fast idling by pulling the choke should happen regardless of the outside temperature, right?

If so, I'll have to have it checked by a mechanic sooner or later.
Title: Re: Question about the (fake) choke/fast idle knob on the 1500
Post by: Troll on April 14, 2025, 07:15:18 AM
The "choke" cable pulls a cam on the throttle body that raises the idle slightly. If used in conjunction with a working set of idle solenoids, it will raise the idle enough to prevent an over rich cold mixture, and the abrupt drop in idle speed that occurs when the idle solenoids stop.
Title: Re: Question about the (fake) choke/fast idle knob on the 1500
Post by: Fab on June 30, 2025, 14:20:21 PM
Quote from: Troll on April 14, 2025, 07:15:18 AMThe "choke" cable pulls a cam on the throttle body that raises the idle slightly. If used in conjunction with a working set of idle solenoids, it will raise the idle enough to prevent an over rich cold mixture, and the abrupt drop in idle speed that occurs when the idle solenoids stop.

I just realized that I forgot to post an update on this.

The cam pulled by the choke cable was hitting the end side of a small screw.
Apparently the screw is used to adjust the idle rise by pulling the choke cable all the way out.

The tighter the screw, the more its end sticks out and reduces the cam clearance.
In my case, it was screwed all the way in and thus completely prevented the cam from raising the idle at all.

The screw is mounted horizontally with the head facing the left side of the bike. In addition, there is a small spring between the screw head and the metal plate, probably to hold the screw in place.

I had to lift the tank, use a thin screwdriver from the left side, and loosen the screw a quarter turn at a time until the choke cable started working as intended.

This is a view from the right side of the bike:

choke.jpg

And this is a view from under the tank on the left side:

choke2.jpg

choke3.jpg
Title: Re: Question about the (fake) choke/fast idle knob on the 1500
Post by: Fab on July 02, 2025, 12:33:27 PM
I just found some infor about the "choke lever stop screw" in the service manual, which is listed among the things that should never be touched.... Apparently one of the previous owners (or a service center) didn't get the memo and tightened this screw all the way in, stopping the cam before it could affect idle speed.

choke lever stop screw.jpg
Title: Re: Question about the (fake) choke/fast idle knob on the 1500
Post by: Bucko on July 02, 2025, 16:54:18 PM
Quote from: Fab on June 30, 2025, 14:20:21 PMI just realized that I forgot to post an update on this.

choke.jpg



Good to know.  Thanks for posting.