Cleaning Idle Circuit Without Removing Carbs

[FJ_Hooligan]

I've wondered about the feasibility of this in the past and due to my neglect have finally gotten the opportunity to try it out.

Curses on the Demon Alcohol Ethanol.  I let the weeks get away from me and didn't flush fresh fuel into the FJ for too long and came down with a case of a partially clogged idle circuit(s).  It wasn't terribly bad.  The idle was a little rough but I could accelerate through a slight stuttering and ride comfortably on the needle.  However, just off idle I could feel that one or more cylinders wasn't quite right.  A squirt bottle confirmed that at least 2 cylinders were burning cooler than the other.

So, not wanting to pull the whole carb set I decided to try a different approach.  I removed the tank, unscrewed the Idle Mixture Screws and shot carb cleaner and compressed air into the mixture screw port.  I could see a fine mist coming out of the airbox so I knew I was getting pressure at least through to the air pilot jet.  The question was, could I get enough pressure/flow to blow out the idle jet itself (assuming that's where the slight obstruction was). 

I just got back from a test ride and it appears to have worked.  The FJ accelerates smoothly and cruises with slightly cracked throttle right in the heart of the idle domain.

This method is not without some risk and is NOT guaranteed to work for every clogged idle situation.

The risk is shooting air into the float bowl and driving a float bowl amount of fuel up the main jet and into the intake.  Several things should prevent this from happening.  If the fuel level is low enough to be below the idle jet, the air will escape into the bowl and simply flow out the float bowl vent.  Or, if the fuel level is high enough to cover the jet, the air should bubble through the idle jet and escape out the vent without pressurizing the fuel.

When pulling the needle out, the spring can stick to the needle and then fall back into the mixture screw port.  I had this happen twice.  Both times I fished the spring out and sure enough, the spring had picked up the small washer and o-ring and flipped them over.  I had to dig the washer/o-ring out and reinstall it correctly.  So if you attempt this go ahead and pull the spring and verify the washer and o-ring are still in the correct orientation.

If the idle jet/circuit is really badly clogged, chances are the air/cleaner will just blow out the air pilot jet and not clean out the jet obstruction.

I'm pretty happy with the results and not having to pull the carb assembly.  Hopefully this will also work on my son's FZ1.  But those mixture screws are on the bottom of the carb and really awkward to get at.

Good luck to anyone who tries this.  Report success or failure.

[FJ_Hooligan]

For those of you with pod filters, you can block the air pilot jet and the pressure should blow through the idle jet. 

Same warnings as before apply.