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looking for a Carb diagnosis confirmation

Started by Motofun, July 20, 2020, 01:13:16 PM

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Motofun

I finally got the '85 FJ out of hibernation.  It has Pods, a stage 1 kit and a Vance and Hines pipe.  Anyways it runs strong but won't idle for sh*t.  I tried adjusting the idle stop but it doesn't make any impact.  I was trying to do a carb sincro (sp?) but failed when I couldn't get it to run at idle.  Last year I put it to bed with pure gas and stabil, if that matters.  I figure either the idle (pilot) jets and/or the idle air jet are FUBAR.  I've got 5 projects in various stages of (dis)repair and was hoping to avoid a sixth......I'm pretty sure I need to go through the carbs again (it's been years) but thought I'd go fishing here for a miracle. :flag_of_truce:
'69 Honda Trail 90
'75 Honda CB400F
'85 Yamaha RZ350
'85 Yamaha FJ1100
'89 Yamaha FJ1200
'09 Yamaha 125 Zuma
'09 Kawasaki KZ110 (grand kids)
'13 Suzuki GSXR 750 (track)
'14 Yamaha FZ-09
'18 Suzuki GSXR 1000R (track)
'23 Yamaha Tenere 7
SOLD: CBX,RZ500,Ninja 650,CB400F,V45 Sabre,CB700SC,R1

Motofun

Quote from: Motofun on July 20, 2020, 01:13:16 PM
I finally got the '85 FJ out of hibernation.  It has Pods, a stage 1 kit and a Vance and Hines pipe.  Anyways it runs strong but won't idle for sh*t.  I tried adjusting the idle stop but it doesn't make any impact.  I was trying to do a carb sincro (sp?) but failed when I couldn't get it to run at idle.  Last year I put it to bed with pure gas and stabil, if that matters.  I figure either the idle (pilot) jets and/or the idle air jet are FUBAR.  I've got 5 projects in various stages of (dis)repair and was hoping to avoid a sixth......I'm pretty sure I need to go through the carbs again (it's been years) but thought I'd go fishing here for a miracle. :flag_of_truce:
I'll add that I rode about 100 miles yesterday and added sea foam to the gas but that didn't seem to make a difference.
'69 Honda Trail 90
'75 Honda CB400F
'85 Yamaha RZ350
'85 Yamaha FJ1100
'89 Yamaha FJ1200
'09 Yamaha 125 Zuma
'09 Kawasaki KZ110 (grand kids)
'13 Suzuki GSXR 750 (track)
'14 Yamaha FZ-09
'18 Suzuki GSXR 1000R (track)
'23 Yamaha Tenere 7
SOLD: CBX,RZ500,Ninja 650,CB400F,V45 Sabre,CB700SC,R1

Waiex191

Sounds very familiar.  I'd check to see which pipes are cold.  That helped me track down the issue.  It is unlikely to be a carb synch problem.  The pilot jets are easy to get to when the carbs are out. 

Generally fishing for miracles doesn't work - carbs don't self-heal!  Though I confess I was hoping for a miracle as well.

With no stock airbox to reattach, your task is about half of one of us stock bike guys.
Bryan
1989 FJ1200
1981 Suzuki GN400
Poplar Grove, IL
 

Motofun

Victory,,,sort of.  The pilot jets were in fact plugged.  It's been a while since I did the carbs so I naturally forgot to drain them (I thought I had run them dry).  Funny how there's still enough gas in them to soak a pants leg when you turn them upside down....Anyways, it runs and idles and is synch'd...20cm of mercury at 1100 rpm which seems about right.
'69 Honda Trail 90
'75 Honda CB400F
'85 Yamaha RZ350
'85 Yamaha FJ1100
'89 Yamaha FJ1200
'09 Yamaha 125 Zuma
'09 Kawasaki KZ110 (grand kids)
'13 Suzuki GSXR 750 (track)
'14 Yamaha FZ-09
'18 Suzuki GSXR 1000R (track)
'23 Yamaha Tenere 7
SOLD: CBX,RZ500,Ninja 650,CB400F,V45 Sabre,CB700SC,R1

fj1289

Good deal!  Also, you got to add another project to the list and scratch it off the list - Progress!

FJ_Hooligan

I kind of hesitate posting this tip because it's a lazyman's technique that doesn't always work, but it can delay the inevitable cleaning if you want to get a ride in.

Pull the idle mixture screw out and make sure you get the screw, spring, washer and o-ring out,
Shoot a squirt or 2 of carb cleaner into the mixture port,
Then hit it with compressed air.

Most of the cleaner and air will immediately go out the idle mixture outlet port or the progression ports.  But, occasionally I've managed to use this to clear a partially obstructed idle circuit without removing the carbs.

No guarantees, but worth a shot, as long as you weigh the possibility of losing one of the idle mixture components.

DavidR.