ST 1300 Runaway Idle

[RVtraveler48]

I have a 2009 ST1300A with 86,000 miles on it. A few days ago the idle speed began to run away - just under 4,000 rpm. Prior it idled at about 1,000 rpm. It's intermittent - I ran one errand with it racing, then came out it started and idled properly. The coolant is right, operates at normal (3 bars) temperature. I bought a Japanese Phillips screwdriver to fiddle with the idle - exercise it - had no effect. I don't think it's the wax gizmo since all that does is return the cold idle (1600 rpm) to 1000 once warmed up - that has been consistently fine. And I don't think that would cause it to race. I just came up from the garage and it ran away again - wondering if it will be find in the morning when I'm supposed to ride with some friends. I don't mind digging into the intake manifold level if I had some idea what I'm looking for - broken spring? I'd guess rodent but it's garaged LOL. Help!! Peter

Update: in digging down to the airbox I found raw gasoline on TOP of the Left Front Cylinder butterfly valve. I can't imagine how gas got there, but I can see how it might cause the idle to race. Hoping this will clue another member in as to what is going on. Thanks!

 

[oude geit]

If not the wax valve, which should start a cold idle about 2000 then go down, would guess vacuum tubing, tee, or flow of coolant through the wax valve.

 

[OldMcClelland]

probably low on coolant. check the actual system cold (not the overflow bottle). Mine did this and simply topping it off fixed everything.

rob

 

[Cortina]

I have the same issue , have convinced myself it's the wax valve , and I am about a day away from removing it to check (other jobs getting done on route) .... it's well burried in there. (When I say check it - the valve itself + the water pipework in both directions ... I suspect a blockage ?)

 

[Andrew Shadow]

Its the SE thermal valve, i.e. wax valve. It may not be the thermal valve itself, it may be the linkages connected to it that are binding and need a good cleaning and lubricating. It could also be that the coolant to it is being restricted due to a blockage, which is preventing a rapid warm up of the wax. The reason it is normal after you have run it and then restart it again is because the hot soak time allowed the ambient heat from the engine to warm the thermal valve enough to overcome any linkage binding or lack of coolant flow.

 

[Terminator2]

My cold choke was nearing 3k. Just found one of the 5 way-T hoses at number #1 cylinder vacuum port fell off March 2024. Re-installed hose. Now cold choke idle @2k rpm. I've ordered correct oem vacuum hose 4.5mm I.D. x 1000mm (39 inches long) from Honda (#95005-45001-50m). That's what I get for installing U.S. size vacuum hose. Note: Clean inside hoses and ports (exterior) with alcohol-no slippage.

 

[Fawlty]

Check your radiator isn't blocked up, just in case.