#1 running lean

Checked my plugs after a ride and #1 is like white white. This cyl supplies vacuum for the petcock, the line seems to be ok, but I am replacing it tonight. Any other reason it is leaning out? Haven't had the carbs apart but pulled the bowl off one and the jets and emulsion tube looked fine.

 

I just went through this issue - on #4. It was leaking air at the gasket where the intake manifold connects to the head. After reading reams and reams of threads about lean running cylinders, it's usually advisable to clean the carbs - paying attention to the 'clunk' test and making sure the floats are doing what they're supposed to do and making sure the jets aren't clogged. A propane test seems also to be advisable to ensure no leaking is happening anywhere around the throttle seals.

 

Suck on the hose connected to petcock if you draw in air its leaking, it does not matter which cylinder the hose is hooked to so try moving it to a different cylinder and see if lean condition follows it. Clogged jets, low float height, stuck float, stuck needle jet, plugged emulsion tube, hole in diaphragm can all cause lean condition

 

Undo the Supply Hose from the Petcock to the Carbs.
Drain the No.-1 Fuel Bowl and leave-out the Drain Screw.
Get a Rubber Ear Syringe (Figure-1)
Remove the Top of the Carb.
Remove Spring and Diaphragm Assy
Remove Aux Plate if equipped.
Use the Syringe to flush ((Back-flush)) the Pilot System.
Fill the Syringe with some Carb Cleaner and stick the Nozzle of the Ear Syringe right in to the Pilot Air Jet, ... squeeze.

Take-out the Pilot AIR Jet ... Flush
Block open passages with Oiled Q-Tips or fingers.

See if there was something that got loose.
Hook a Hose to the Fuel Bowl Drain Nipple.
Blow a Jet of Compresses Air over the end of the Hose to Vacuum-out the Fuel Bowl ... with the Drain Screw OUT.

Fig. 1 / Syringe:

 

Make sure the brass vacuum nipple itself isn't loose in the intake manifold; I've had it happen.

 

Thanks. I don't have a brass nipple, on the seca 2 the vacuum nipple looks to be cast into the intake runner. I'll try the suck and propane tests before I rip the carbs apart, thanks for the detailed instructions Rick.

 

Did you find the issue with #1...I am havign a similar issue with my XJ750 seca...