Escalating idle speed

Hey all,

Took my ST1100 out of the garage recently for a short trip (1hr each way). Took a while to start her up, no big surprise because of being in the garage for near 8 months, and once on the highway everything was fine. Got to destination 1 and when pulling into the parking lot noticed the idle was a bit high (2-2.5krpm).

Went inside, did my work stuff, hopped back on to come home and the idle seemed ok - not quite at that 2k mark from the start - but when getting off the freeway near my house and coming to a stoplight, the idle RPM was now 3k'ish. By the time I went a few more lights to get home it was 4k.

The only time it would go lower is when the engine was actually engaged. The last light before my house I literally killed the engine at the light so it wouldn't just sit there and race full open with no flowing air over it from movement.

Now for starters, I'm pretty sure the throttle isn't stuck. When it's idling at those crazy high speeds I can touch the grip and it will go even higher - throttle cable engages immediately. It will also return to a rest position immediately and feels taut and ready for another grab.

I was thinking maybe air filter, I haven't changed/cleaned mine in a while. I pulled open the body and removed the air filter to eyeball it. It's a K&N and has an additional about 3/4" foam cover on top of just the usual circular/cylinder air filter. Nothing seemed particularly dirty but I suppose I can wash out that foam cover in case it's gotten clogged up - assuming bad air flow will cause this kind of behavior to start with.

Ideas?

Thermal wax unit.

http://www.st1300.us.com/showthread.php?t=3283

It's designed to adjust the idle up when the engine is cold. You more than likely have blocked passages.

Had the EXACT same issue with my Trophy after it sat too long - I believe the problem was plugged / partially plugged low-speed jetting (or idle jet?) - so it was idling too lean and therefor fast. It resolved itself through frequent long rides with abundant sea-foam and fresh gas. A better solution would have been to remove and thoroughly clean the carbs, almost surely.

Why do I think it was lean? When it had the fast-idle, I checked the exhaust header temps (I have one of those infra-red temp sensor pistol things). The headers (there were 4) of #1 and #4 were the same, and #2 was a bit higher, #3 was a lot higher.

As you stated, it ran fine - but at idle was too fast.

Another possible cause - stuck butterfly (not likely) or sticking (crap - what's the carb part that raises and lowers under the diaphragm...?).

Neil

yep, semi clogged pilot jet/s or possibly sticking choke plunger.

I seriously doubt it is that strange wax gizmo because the ST1100 is carbureted and don't have the strange wax gizmo the fuel injected ST1300 has.

the ST does have a fan so it is capable of cooling while sitting still but with a leaned out idle mix and idling up high the exhaust will get extremely hot and there could be a fire hazard from sitting reved up.

Tiger: Check your throttle cable adjustment, touching the throttle should not cause an increase in engine speed, a little slack is a good thing.
Good luck
Smoky

Leon: You are correct: There is no wax thermal unit on the ST11.
Smoky is also correct, you do need some slack - I believe the book says 3-5mm, but that could be wrong. It's a good measure to use, though.

The ST11 has a manual choke. It could be sticking, but it's unlikely. Clogged jets - with ethanol in play - is more likely, and cracked vacuum hoses.

Have you done the PAIR removal process?

he did say it had sat for 8 months, I am surprised it even started.

it is not going to be easy or fun.

chaissos said:

Leon: You are correct: There is no wax thermal unit on the ST11.
Smoky is also correct, you do need some slack - I believe the book says 3-5mm, but that could be wrong. It's a good measure to use, though.

The ST11 has a manual choke. It could be sticking, but it's unlikely. Clogged jets - with ethanol in play - is more likely, and cracked vacuum hoses.

Have you done the PAIR removal process?

Click to expand...

Crap, sounds like I need to drop her off and let a mechanic go from stem to stern on the engine, just about. I'd forgotten about ehtanol as part of the fuel these days and the effects it can have on the engine (a little water if you're lucky, eroded seals and tubes if you're not). F'ing corn lobbyists.

I'm reluctant to even try to start her up again to get to a shop, plus the one I used regularly closed because of the owner's bad health. I really don't want to go back to Woods Fun Center in Austin, they bend you over a barrel on cost for the tiniest little thing.

Can anybody recommend a good small repair shop in Austin?

Definitely clean your air filter. It could be a problem after eight months, the oil in the filter sets up and plugs the filter. Also, run a can of Seafoam through the system. If there is some residue build up it might just clean it up. I had an old Oldsmobile running ratty and the mechanic pulled me aside and said, "run some engine cleaner through it, that's what we do!" And it worked. The shop is no longer in business.

It's just the carbs. Happens all the time. These aren't all that difficult to do, just tedious, and some STuff in the way. Seafoam might fix it - try that first. It's cheap and easy. Do a couple/three tanks of it and see where it gets you. Running at a high RPM won't hurt it. Heck, I imagine you've run it up to 5-6K or more, anyway. I do regularly.

Here's a good instruction page to assist you if you determine you need to rebuild. Read through it first to make sure you can/want to do it before starting. Even if you have someone else do it, a lot of the beginning steps can bring the price down (plastics removal).