2008 Honda St1300 Dies on Idle , runs Fine

DonutDonut

Joined
Oct 4, 2021
Messages
8
Age
33
Location
South Africa
Hi all,

I have a 2008 Honda St1300. The bike started to die in town at stop lights and struggled with power.

I replaced plugs, air filter , fuel pump.

Tonight I drove it for about 15km and it was all good until I stopped at home and it died again. If I start it, it starts up, idles a bit and then dies.

What may be the issue for this ?
 
First thing I would check would be your battery, is it a factory battery in good condition, or a smaller internet purchase?
Does your voltage drop when you turn the key on, hit the starter, and put a load on it?
If the battery is strong, and the ground wires are clean and connected correctly, the next thing I would check would be the 5 way tee from the map sensor switch to the TB housings, and see if its clogged up.
I really hate to throw my 3rd suggestion into the mix, but are your brakes dragging?
Inspect your SMC (function test) search the forum, and see if your rear brake is locking up and dragging.
Does the bike seem to die when you pull the clutch in? (like stalling because the brake is holding things back?)
Some other things to check....when was the last time you changed the coolant and/or t-stat?
Your t-stat could be frozen open, causing the ECU to run a an over rich mixture (think running with your choke on)
When you check your idle, be sure to use a driver to adjust it, and not turn the knob by hand etc.
let us know what you find, and we'll see if we can help.
Good luck.
:WCP1:
 
Igofar said:
First thing I would check would be your battery, is it a factory battery in good condition, or a smaller internet purchase?
Does your voltage drop when you turn the key on, hit the starter, and put a load on it?
If the battery is strong, and the ground wires are clean and connected correctly, the next thing I would check would be the 5 way tee from the map sensor switch to the TB housings, and see if its clogged up.
I really hate to throw my 3rd suggestion into the mix, but are your brakes dragging?
Inspect your SMC (function test) search the forum, and see if your rear brake is locking up and dragging.
Does the bike seem to die when you pull the clutch in? (like stalling because the brake is holding things back?)
Some other things to check....when was the last time you changed the coolant and/or t-stat?
Your t-stat could be frozen open, causing the ECU to run a an over rich mixture (think running with your choke on)
When you check your idle, be sure to use a driver to adjust it, and not turn the knob by hand etc.
let us know what you find, and we'll see if we can help.
Good luck.
:WCP1:
Click to expand...
Dam, this is why this site is so great, you guys know tons of stuff. I just bought a Victory and I am on a site like this for those bikes, but they do not get into the technical aspects like you guys.
 
Possibly a vacuum leak? Often caused by aging lines fittings and components of vacuum operated cruise control. Especially suspect if cruise does not hold speed or will only hold a limited speed. ( i.e. will hold steady at 65 mph but not 80 mph) Happened on my bike, it would start right up but would not idle. Ran fine at 3000 and above rpm. About drove me crazy! Was a cracked vacuum hose. Removed the vacuum source for the cruise control and bike was instantly back to normal!

Welcome from South East Georgia U.S.A. Edit: I also replaced fuel pump & filter, spark plugs, coil wires and spark plug caps. And No Joy from any of those.
 
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OkieRider said:
I didn't know that. Does the knob not directly turn the same thing?
Click to expand...

The knob does do the same thing, but you cant reach it with the fairings on. ( I cant anyways) I think the knob is mainly for grabbing it and pushing in or out. You push in before you turn the knob or screw, then pull out so it locks in place.
 
Great, thanks for that - I didn't know it had to be pushed or pulled, either. I haven't messed with it yet, but I think I need a smidge higher idle.
 
Interesting. I have no idea what kind of path it runs. Is it fairly straight from the knob to the idle adjust screw?
 
No very sharp turns, but it goes over, under and across a lot of stuff.
The illustration in the shop manual isn't that good. Maybe Michael (@CYYJ) has a good picture for you.
 
OkieRider said:
So, to adjust it, you have to jostle a lot of stuff?
Click to expand...
you don't have to remove the side cowling, to access the idle adjuster. Suggest using the JIS screwdriver,,, from your bikes tool kit. Instead of twisting the knob,, just use the JIS screw,,, that is in the center of the knob. Taking the pressure off the idle stop is necessary,, by just advancing the throttle a bit. This is usually a fine adjustment,,,, cheers,, CAt'
 
Andrew Shadow said:
No very sharp turns, but it goes over, under and across a lot of stuff.
The illustration in the shop manual isn't that good. Maybe Michael (@CYYJ) has a good picture for you.
Click to expand...
That whole idle adjustment mechanism on the ST 1300 is not what I would call the finest example of Honda engineering.

Unlike the idle adjuster on the ST 1100, which is a Bowden Cable (a cable that rotates within a stationery outer sheath, like your throttle cables), the idle adjuster on the ST 1300 is a single monolithic part - the entire thing, knob, external sheath, and whatever might be inside it - rotates as one piece. I posted a lengthy description about this at this post: Idle speed, for that reason I won't repeat it here, go read that post.

The ST 1300 cable is subject to fouling (external interference) in numerous areas. There is a small white collar on the external (knob) end of the cable that holds the cable in place in a U-shaped bracket on the side of the bike. The cable should rotate freely within that white collar, but after 10+ years of riding it's not unreasonable to expect that the cable won't rotate freely within that collar. So, step 1 is to lift the cable out of the U-shaped bracket before you attempt to adjust idle speed. You can put it back into the bracket once you are done.

Rotate the throttle grip slightly before attempting to turn the cable. This will relieve pressure from the inside end of the cable and make it much easier to turn the cable.

The biggest problem, though, is that on its way from the knob end to the other end that touches the throttle body assembly, the cable has to pass through an absolute jungle of coolant hoses, vacuum hoses, electrical cable bundles, the rubber heat mat, throttle cables, and then navigate its way through the forward portion of the throttle body assembly. If the cable is squeezed or pinched against any of those items, it will be fouled and thus not able to rotate freely. If it was a Bowden cable, it wouldn't have this problem... the outer sheath of a Bowden cable remains stationary at all times, protecting the inner cable which is the part that rotates.

If you don't want to have to take the bike apart (lift the upper fuel tank, and remove both sections of the airbox), your best chance of freeing a stuck cable is to remove it from the U-shaped holder at the knob end of things. This will give the cable a bit of slack, and might enable it to move free of anything it is binding against down in the V of the engine.

If you don't have any luck doing that, you will need to remove the upper fuel tank & the entire airbox, then visually inspect the cable to see where it is binding. Try to move the object it is binding against out of the way, and lubricate the outside of the cable where it was binding with silicone lubricant.

Below are a few photos that might help you understand the routing path & the source of the problems.

Michael

Idle Adjustment Knob (as built from the factory)
Idle Adjustment Knob.jpg

Idle Adjustment Knob removed from U-shaped bracket for easier adjustment
Just pry the white collar straight up to release it from the U-shaped bracket.
Idle Adjustment 2.jpg
The mess of hoses, tubes, wires, mechanisms that the cable can bind on
line shows approximate path cable takes UNDER all this crap
Idle Cable Path.jpg
 
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Igofar said:
Use the driver to Push it inward to unlock it, adjust it, then Pull the knob back outwards to lock it back into place so your idle won't wander
Click to expand...
CYYJ said:
the idle adjuster on the ST 1300 is a single monolithic part - the entire thing, knob, external sheath, and whatever might be inside it - rotates as one piece.
Click to expand...
These two statements don't seem to square with one another.
If the idle speed adjustment cable is all one solid piece that rotates as one solid mass, i.e., there is no part of it that is capable of moving independently relative to any other part of it, what moves in and out against what, and what is it unlocking and locking?
 
Gus1300 said:
Just one question. Whose bike is THAT, and how does it stay so CLEAN!?
Click to expand...
It's mine, it has 70,000 miles on it. I don't know how it stays clean... it doesn't seem to get dirty. Probably because I don't like riding in the rain.

Michael
 
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