I have a hypothesis that I need confirmed.

Bike starts OK with the choke open, but won't stay running if I close it. The fellow I bought it from already cleaned an synchronized the carbs (you've probably seen that one a million times, but I trust him) and I was already having issues with the petcock. Could it be as simple as a faulty petcock, or would the bike not run at all if that were the case? My other thought is that the idle maybe got super out of whack somehow. Check the simplest things first, right?

Probably unrelated, but I think the clutch cable is slack, as I am still feeling engine grab when I pull it in. I will check that tomorrow when there is daylight.

 

Need to clean the carbs again. Slow speed circuits(pilot jets) are most likely clogged. They are the hardest to clean because they are the smallest orifices. K&L makes a cheap carb jet cleaner. Of course, check the idle speed 1st, but I'm fairly sure you're gonna need to pull the carbs again.

 

Crap. I am so damn sick of dicking around with carburetors I could spit. I shouldn't have gotten ANOTHER carburetted vehicle.

 

I've been into my ST1100 carbs three times so far, and I still haven't got it right. Apparently 4 times is the lucky charm so that is good news...

There are three paths for fuel to get into the engine.

The enrichener circuit (aka choke)
The low speed circuit (aka pilot or idle)
The high speed circuit (main jet/emulsion tube/needle)

Idle and low speed running is controlled by the pilot circuit, so through the pilot jet (which as Jev says is really tiny), this feeds through the needle valve (or pilot screw) and feeds to some really, amazingly tiny holes in the floor of the carb right under the butterfly, and a larger one just downstream of that. You need to be able to push carb cleaner through all of these to ensure a steady idle.

Certainly check the idle adjuster first, you should be able to raise and lower the idle speed when warm if all the circuits are clean.

Regarding the petcock, I would have thought this would either work or not.

You have a hydraulic clutch so best option would be to flush fresh fluid through the line and bleed any air from the slave cylinder.

 

**UPDATE**

It ended up being a combination of two factors; the mixture set screws on the carbs and the idle adjustment. I set the idle screws back to factory (they were a little too far out, but equally so on each carb) and fiddled with the idle until it was idling at roughly 1400 rippems.

Next question: the bike is idling OK without the choke, but the idle won't stay steady. It periodically goes up to almost 2500 rpm and then settles back down at 1400. What could be causing this? I also noticed a distinct smell of unburned fuel coming out of the left tailpipe. What the hell does THAT mean? Are the two related?

As for the clutch, I topped off the reservoir (which was pretty low) and tomorrow I'll see if that was the issue. If not I'll bleed the clutch and try again.

As always, you guys have provided some great info. Between you all and the Clymer manual I feel like I could tackle just about anything!

 

One thing that gives uneven idle speed is the carb balance, basically the adjustment of the throttle butterflies so they are all passing an eve amount of air, as measured by the inlet tract vacuum. If that doesn't settle the idle down then you are back to the pilot screws.

 

An oil change seems to have fixed the issue, oddly enough. Now the bike is idling at a cool 12-1400 rpm.

 

I'd chalk that up to a coincidence. Maybe you still had a slight blockage that cleared itself out. But whatever happened, if it's running good then I'm happy for you.

Also, do a search on here for the PDF file of the Honda factory service manual. It's leaps and bounds above the climer manual.