Auto choke

[deej]

A couple of months ago my bike started running a little rough at start up. It feels like the choke is not working or the initial start circuit or whatever these bikes have. What usually happens is I start it and it barely idles and usually dies because its idling so low. This morning I decided not to let it warm up and started it and took off on my 75 mile ride to work. It ran a bit rough but seemed fine at highway speed and then at the first stop light when I pulled in the clutch it died. It usually runs at normal idle once its warmed up, but it didn't this morning. 65 of my 75 mile commute is a two lane with no stops so I didn't get a chance to see what the idle was doing, but when I got to work it was idling perfect at about 1100. Has anyone ran into this before? I was looking at the service manual on changing out the fuel filter, seems its located inside the tank. Its also been a couple of years, and if I'm honest its probably been 5 years since I looked at the air filter. would this be a good place to start? Can a shop put an analyzer on it and see what might be causing this? This is the first real issue I have had in the over 10 years I've owned the bike, so I guess that's not too bad. I got the bike with 19,000 miles and now I have 50,000 Any help would be very much appreciated. I've included a couple of pictures just because its been a while and I wanted to see if I still remembered how to upload one.

 

[Igofar]

Standing by the white courtesy phone.

 

[Jethro]

When it is warm,does it”bog down” at acceleration.?.Check air filter first—easiest.then phone igofar for further pondering.

 

[aniwack]

You had me at "choke is not working". The ST1300 is fuel injected and has no choke. Easy fix before you bug Igofar. You need to lift the tank, clean all the junk out of the airbox, and remove the airbox to access the throttle body. Igofar will brief you on how to use Marvel Mystery Oil to clean out the buildup and do the throttle body sync. Make sure you have a fan to blow the exhaust out of your garage.

 

[deej]

When it is warm,does it”bog down” at acceleration.?.Check air filter first—easiest.then phone igofar for further pondering.

No bogging, runs perfect

 

[deej]

You had me at "choke is not working". The ST1300 is fuel injected and has no choke. Easy fix before you bug Igofar. You need to lift the tank, clean all the junk out of the airbox, and remove the airbox to access the throttle body. Igofar will brief you on how to use Marvel Mystery Oil to clean out the buildup and do the throttle body sync. Make sure you have a fan to blow the exhaust out of your garage.

Well if it doesn't have a choke then why does it idle high for a few minutes and then come down to a normal idle, or at least it did this for 10 years. Maybe calling it a choke was the wrong term but its is like an auto choke.

 

[wjbertrand]

It has a wax motor (with a coolant passage) that opens what are called starter jets when the engine is cold. The ECM delivers a richer mixture based on engine temperature, and the starter valves admit a little extra air to go with. Once the engine has been running a minute or so the wax motor extends a linkage that releases the starter valves, allowing them to close. they are spring loaded. What you are describing sounds like a pugged up vacuum line or the 5-way vacuum "T" under the air cleaner. First step would be to blast out all 5 lines and the T to make sure they're all open.

 

[deej]

It has a wax motor (with a coolant passage) that opens what are called starter jets when the engine is cold. The ECM delivers a richer mixture based on engine temperature, and the starter valves admit a little extra air to go with. Once the engine has been running a minute or so the wax motor extends a linkage that releases the starter valves, allowing them to close. they are spring loaded. What you are describing sounds like a pugged up vacuum line or the 5-way vacuum "T" under the air cleaner. First step would be to blast out all 5 lines and the T to make sure they're all open.

ok I'll check that out. Thanks!

 

[Igofar]

Both your explanations and descriptions are wrong….what do have have for them Bob?
Thanks for playing though.
Standing by the white courtesy phone…

 

[ddemair]

It would be helpful if you posted WHY "Bob" is wrong.

I'm pretty sure not all of us know who Bob is or what he said and since this is a forum intended to share information, please share your thoughts as to what might be the issue here. Many of us could benefit.

 

[Igofar]

Bob was a game show person….you may not be old enough to know that, sorry.
I will try and post pictures of the unit in a bit.
Busy helping other members at the moment.

 

[deej]

Okay, so my bike sat all day at work and I mean like 14 hours, and I went to start it and it started right up and idled high just like normal and within 2 minutes or less engine came down to a perfect idle Now I'm sure it didn't fix itself and I'm almost positive that it'll do it again, So when I head home tomorrow after work I'll see what happens I'll let you know.

 

[Sadlsor]

Bob Barker - The Price Is Right?
Bob was the host, and IIRC he had an assistant, whom he would ask, "What do we have for him, ---?"
I don't recall the name of the assistant, but it matters not.
Sorry for the hijack, but that's what I do, and I am who I am.
But I have learned to listen to @Igofar because he has about the best diagnosis success rate of anyone around.
Think Sherlock Holmes.
Maybe Larry read a lot as a kid.
I know he's read all the Honda service manuals.

 

[aniwack]

Okay, so my bike sat all day at work and I mean like 14 hours, and I went to start it and it started right up and idled high just like normal and within 2 minutes or less engine came down to a perfect idle

That's the normal startup sequence.

 

[jfheilman]

Just for the record, I had a similar event (not exactly the same but similar) last year (documented here. https://www.st-owners.com/forums/threads/fi-light-diagnosis.174265/#post-2260800).

I actually never did clean the five way and the bike has worked ok since then. It does not get the same work out that it use to when I use to ride 30 miles to work one way. But.... I do try and ride it two or three times a month for 30 to 50 miles.

It might have been possible that the five way was clogged and then unclogged as I rode it home.

Anyway, just wanted to provide some additional context.

 

[Igofar]

Attn: Mellow
Please don't Delete all of this thread, as the pictures and explanation may help members to understand how this unit works, and how to correct roaming idle issues.
Now both of you go to your corners, and face the wall for a time out, until you learn how to play nice with each other.
If we start name calling, we'll be no better than ADVRIDER.

 

[Igofar]

Play nice children….while I can’t say I have seen the insides of one, I have seen too many to recall.
Maybe these pictures will clear things up a bit.
Also, an observation that most of the senior techs and master mechanics have not figured out yet, is if/when the black plastic bushing becomes dirty or dry, the threads on the rod can snag and catch on the edge of the hole, or dirt, causing the idle to roam because it prevents the wax valve assembly from working correctly.
Anybody see a diaphragm in this unit?

 

[Sadlsor]

Where does the actual wax live?
For the longest, I thought y'all were actually making this up.
Wax assembly.
Kinda like blinker fluid?

 

[mjc506]

Inside the brass/copper covered cylinder thing. Only a couple grams, if that.

 

[wjbertrand]

Yup, all looks very familiar. Never had any issues with the thread of the pull rod catching on the (that I think is Delrin) bushing. You can see in the second photo how the pull rod of the wax motor opens the starter valves when it cools and contracts. I had an issue where cold idle speed became too low, leading to occasionally stalling. Adjusting that nut on the pull rod (also in photo 2) raises the cold idle speed slightly by opening the starter valves more, admitting more air. The starter valves are quite noisy (you can hear them hissing as they suck in air) when the engine is started from cold with the air box assembly removed. As the engine warms you can watch the wax motor extend the rod allowing the starter valves to close and the hissing noises disappear. Normally this takes only minute, perhaps a bit more.

In researching my cold idle problem I took apart and cleaned out the whole system, adjusted the pull rod and then synched the starter valves. The bike cold started and ran like a dream for 100,000+ miles after that with no further attention to the system.

No disrespect Igofar, but my previous description was not incorrect. Thanks for all your expertise on this list as well.