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Discussion Starter #1
Hi guys-

I installed FCR39s on my SS a few months ago, and while I love them, I've had a few issues and am looking for some direction.

As seems common with these, the idle hangs around 2-2.5k after the bike is warmed up. Checked for leaks with propane, refitted the carbs and cinched them down again, and still it persists. Fuel screws are at 3.5 turns right now, motor is stock except for FBF pipes and a k&n. Bike runs well through the rest of the range, no bogging or backfiring at all. Starts easy and idles smoothly.

Also when warm, the bike will occasionally die at a stop light. Today it happened twice in a row at the same light. Starts easy enough again, but still.

Fuel tank is full, gas is fresh, weather is warm, vent line off to remove that from the equation. Any suggestions?
 

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once warned up, what RPM does your idle settle down to?
 

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Richen it up with the fuel screws one full turn . If the hang goes away, dial it back 1/4 turn at a time until you get it right. Those are mixture adjustment screws, key word, “ adjustment”.
I’ve read that FCR’s are sensitive to cable routing. Flex your cables around while idling , turn the bars etc. See if that has any effect.
 

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1200 rpm is too high for a carby with fcr's.
step 1 turn up idle until bike is warm.
turn down idle to about 1100 rpm
As bike fully warms up from use idle will rise higher and idle will hang, simply turn it down until it no longer hangs up. you will end up somewhere around 1000-1100rpm when fully up to temp.

honestly just lower it as if hangs, a little at a time until it idles but no longer hangs.
 

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Discussion Starter #7
1200 rpm is too high for a carby with fcr's.
step 1 turn up idle until bike is warm.
turn down idle to about 1100 rpm
As bike fully warms up from use idle will rise higher and idle will hang, simply turn it down until it no longer hangs up. you will end up somewhere around 1000-1100rpm when fully up to temp.

honestly just lower it as if hangs, a little at a time until it idles but no longer hangs.
Cool i'll give that a shot. Thanks for the tip!
 

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Discussion Starter #8
Just an update for anyone that stumbles across this in the future. I can't stand coming across threads with no resolution.

So it turns out that the vertical cylinder was WAY too rich. I bought a Gunson colortune, and the vertical cylinder fuel screw was nearly two full turns rich. Horizontal was pretty spot on, so got the colors matched between the two and no more idle hang! Still starts easy, revs easily to redline, and drops back quickly to a nice smooth idle at 1100. It never bogged with the rich setting, but throttle feels much crisper now. So happy to have this one solved.
 
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