Low Idle Speed After High Speed Ride

Just cleaned and rebuilt carbs on 1980 xs650sg. All standard size jets. Man this thing runs so much better!
I synced and adjusted pilots. They ended up about 1 turn out for best idle. About 1200-1300rpm ish.
Took it out for a ride. Perfect around town. Got out on the freeway for a few miles at about 70-75 mph.
At the end of the off ramp, at the red light, the idle speed was down to maybe 750-800rpm ish. Reved the throttle a bit and idle came back up a bit, but not up to normal. After some more slow riding, stoplights idle was fine.
I'm kinda thinking maybe I'm a little lean on the idle circuit? Maybe richenup the pilot a half a turn?
Whaddya think?
Thx!

When you say you adjusted the pilots, do you mean the mixture screws? One turn out is quite lean for your carb set. Normally, it likes something in the 3 to 3.5 turns out range. The BS34s were very lean from the factory, borderline too lean in my opinion. Even a totally stock bike will be happier if you increase the mains one size (132.5 stock to 135), and to richen up the idle circuit a little, go down one or two sizes on the air jets (135 stock to 132.5 or 130).

5twins said:

When you say you adjusted the pilots, do you mean the mixture screws? One turn out is quite lean for your carb set. Normally, it likes something in the 3 to 3.5 turns out range. The BS34s were very lean from the factory, borderline too lean in my opinion. Even a totally stock bike will be happier if you increase the mains one size (132.5 stock to 135), and to richen up the idle circuit a little, go down one or two sizes on the air jets (135 stock to 132.5 or 130).

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Yes I was referring to the mixture screws. I did set the mixture screws at 3 turns out initially, but the idle didn't change much in speed or smoothness until I got them set at 1 turn out. I am riding at a little above 3000ft in elevation.
Do you think the behavior I describe is too lean an idle circuit?

It does sound like a lean condition, but it may not be the idle circuit. Are your floats set correctly? If they're off (set too low), that can cause lean running. But you could try richening the mix screw setting to see if it helps. You can't really set the mix screws by ear on the BS34's like you can on the BS38's. Adjusting them has very little effect until you get them really far open or almost closed. I set them using small throttle blips. I watch for a hanging idle speed or popping. This indicates I'm getting too lean on the screw setting so I'll open it back up until the popping goes away.

Notmyrealname said:

Just cleaned and rebuilt carbs on 1980 xs650sg. All standard size jets.
I synced and adjusted pilots. They ended up about 1 turn out for best idle. About 1200-1300rpm ish.

Click to expand...

Technically your right. Each Pilot screw will have slightly different settings. On my 83 bike, one screw is just over an 1/8th difference in setting. A visual of the Carb workings.

Floats were set with a clear tube, they are pretty much spot on. Thanks for the tips. I'll play around with it some more, and I have some Mikuni jets on order. See if fattening it up a bit will help. Good to kinda confirm my suspicions of a lean condition. Thx!