SOS - ST1300 stalling after idle adjustment

JingleJ

Joined
Feb 7, 2025
Messages
11
Age
37
Location
Singapore
Bike
ST1300A
Hi All,

Seeking additional big brains for troubleshooting. Been riding my 2010 ST1300 for about a year, aside from some engine gasket leak there was not much major issues. Recently the automatic fast idle stopped working in the mornings which prompted me to try adjusting the idle speed. The original idling speed was around 900 to 1k but after trying to adjust the idle speed higher, the bike stalls gradually and the idle does not increase despite the adjustment screw turned clockwise around half a turn. Current condition is that the bike can't even keep idling no matter how I try to adjust the idle settings.

Things that I have tried:

- removed 5 way Tee for inspection, its not choked, cleaned it out and replaced all the vacuum tubes with original Honda hose that I have ordered.
- replaced a new MAP sensor.

Thanks for the assistance in advanced!
 
Do you have a cruise control? they often have vacuum leaks. If no cruise control disregard this reply! good luck this will be easy to fix but possibly hard to find.
 
diferg said:
Do you have a cruise control? they often have vacuum leaks. If no cruise control disregard this reply! good luck this will be easy to fix but possibly hard to find.
Click to expand...
No cruise control installed, stock to the teeth.
 
JingleJ said:
Hmmm I’m not sure what actuator you are referring to. Valves n linkage seems ok.
Click to expand...

Good info in this post and related thread.

"Wax" Idle control unit. | ST1300 Related

Andrew put some really good comments out there. Your not going to find anything wrong with the idle wax assembly, other than the damage you caused by changing the adjustment on the factory preset nut, that the service manual clearly indicates NEVER to change the settings. Many of the folks who...
www.st-owners.com www.st-owners.com
 
MidLife said:
Good info in this post and related thread.

"Wax" Idle control unit. | ST1300 Related

Andrew put some really good comments out there. Your not going to find anything wrong with the idle wax assembly, other than the damage you caused by changing the adjustment on the factory preset nut, that the service manual clearly indicates NEVER to change the settings. Many of the folks who...
www.st-owners.com www.st-owners.com
Click to expand...
I see, you meant the wax valve, yes, checked it. But don’t think this is a cause that will make the engine stall since it just holds the starter valves open more than they need to be for the high idle rate. Just wondering out loud, will un-synchronised starter valves cause engine to stall? Or will the starter valves choke causing engine to stall?

Things that I’m suspicious of are mostly sensors or electrical. Worst case is ECU.
 
JingleJ said:
Weak and low idle rpm in the range of 500++.
Occasionally stalls at traffic light stops.
Click to expand...

OK. Makes more sense. Your original post sounded like you were adjusting the idle only because of a startup issue.

Still running fine once you get rolling?
 
MidLife said:
OK. Makes more sense. Your original post sounded like you were adjusting the idle only because of a startup issue.

Still running fine once you get rolling?
Click to expand...
Yes, it runs fine when on the highway and regular rpm of 3-4K. Only when it is start/stop traffic that the problem surfaces.
 
Managed to find the root cause of unable to idle. It seems my usual mechanic removed the middle cable of the MAP connector. Connected back that cable and bike could idle again, however, during morning warmup, the fast idle still doesn’t kick in and there are surges during low gear and RPM riding during mornings.

Any idea what could cause these problems?
 

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Igofar said:
Your guy needs to remove the airbox base, pull the map sensor switch and hoses that connect it to the 5 way tee, and clean the tee out with a pipe cleaner and solvent.
Easy fix, but you may have to re-do your starter valve sync afterwards.
Click to expand...

JingleJ said:
Things that I have tried:

- removed 5 way Tee for inspection, its not choked, cleaned it out and replaced all the vacuum tubes with original Honda hose that I have ordered.
Click to expand...
 
Sorry, juggling several things at the moment, didn’t go back and re-read post.
Sounds like maybe his guy plugged stuff back In wrong maybe?
Would not be the first time.
I would be very surprised if the map sensor switch was bad, as I have a drawer of them and NEVER had to replace one before.
Wonder if his guy cleaned the brass nipples, or the connection where the hose connects with the map sensor.
Or used hose that was the wrong size.
Both of these bits of hoses are labeled and said to be the same dia./ size, however, one falls off.
His guy may have also fouled the linkage
In that area while working.
 

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Have cleaned the tee and changed new tubes.
Quite sure the tubes are correct models as it was genuine Honda parts.

Only thing I have not done is starter valve synchronising.
What are the symptoms if the starter valves are unsync?
 
Had the chance to ride the bike to/fro work today, after riding for a period of time and after revving the engine above 4K RPM, observed lost of power and intermittent power surges again.

Gotten to the extend of stalling when moving off after getting off the high way.

Any idea what might cause such symptoms? Could it be an old sensor that couldn’t take the heat of the engine but not completely failing yet?

Appreciate any and all input!
 
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