Starting the engine gives a normal high engine idle as expected. Then idle speed falls ( as engine temp rises) all correct but then seems to go too low,i.e. 600rpm even to the point of stalling out!! Once the bike is ridden and at full temp idle speed is correct at approx 1000rpm! Any ideas what's causing this?
Idle speed - ST 1300 2009
- Thread starter Wurlitzer
- Start date
ToddC
Site Supporter
Plugged up five way T, or the wax thingy for the idle mixture. Check the tech section.
Thanks Todd, I'll investigate what those are!!
Terminator2
Site Supporter
Install T-Adapter at lower fuel tank for Idle and 5k rpm fuel pressure testing. It's on the way before checking 5 way-T....
Try adjusting the idle speed!
The cold idle speed is controlled by the wax unit opening the starter valves. When cold, the SVs are held open for a fast idle, and as the coolant heats up, the wax unit progressively closes the SVs until when fully warm, the SV position is determined only by the idle screw. The behaviour of your idle suggest the wax unit is doing its thing correctly; a common failure is for the small water hoses to the wax unit clogging, and that causes the wax unit to remain cold and keep the SVs open even when the engine is properly warm; a high hot idle is the result, and the idle screw can't change that.
It sounds to me as if the SVs are not quite open enough when the engine is not fully warm. By all means check the 5-way T is clear and consider balancing the SVs, but if that does not fix the issue you might need to slightly change the wax unit "non-adjustable" nut to open the SVs a little more to bring the cold idle speed up a little.
My bike starts at about 1800 rpm, and then sinks slowly; it does hit a low of about 900 until it is properly warmed up, and then sits steady at 1000rpm.
It sounds to me as if the SVs are not quite open enough when the engine is not fully warm. By all means check the 5-way T is clear and consider balancing the SVs, but if that does not fix the issue you might need to slightly change the wax unit "non-adjustable" nut to open the SVs a little more to bring the cold idle speed up a little.
My bike starts at about 1800 rpm, and then sinks slowly; it does hit a low of about 900 until it is properly warmed up, and then sits steady at 1000rpm.