1979 A1 Carb Refurb - Idle Jet Adjustment - not working

2025-01-31 Install Rebuilt Carbs

Before installing, checked that all screws were tight, but the bench synchronization was correct.
Installed the vacuum extensions before plugging the carbs into the boots. Easier that way.


Manometers hung. I even checked that the restrictions in the tubing were the same for all six. 


Pulled the spark plugs they all look good.
 

 

Installed. And clamped down.
 

I sure hope this works.
 

I would like to ride the bike while the weather is still cold..
 

2025-02-03 No Fuel Air

AdjustmentsToday was the big day. Going to fire the old girl and see if all my carburetor work works.
 

As you can tell by the title, the answer is no. I still have work to do.
 

An initial fire up was running very poorly. Pulled the spark plugs and one and six were very wet, indicating no spark.
Check all the connections, latest sport plugs across the head and spin the motor and they all are sparking. WTFO?
 

 I noticed that one and six has a slightly weaker spark than the others. But for now, she is hitting on all six so let's adjust the fuel air mixture.
I made a tool to access the jet for the inner cylinders.

Unfortunately, the only carburetor that has response to the fuel idle Jeff being adjusted his number three.Carburetors one and two the jet can be fully inserted or fully out and no change in engine response.
Carburetor three, running it in the engine, stumbles. Turning it out it RPM raises.

Three turns out seems to be the sweet spot. This is for both adjustments on carburetor number three.
 



thought perhaps because I had not done a running securization perhaps the fuel air idle circuit was not yet in play.
So I performed a rough running synchronization. Here are the results.

At this point, the bike is idling very well, and is very responsive to throttle. I am kind of debating whether to mess with it or just let it be. 


I pulled the sparkling plugs. Here is the result. One through six left to right.

I don't know why, but the picture makes the plugs. Look better than what they are.
Number one looks a bit oily, to a bit sooty, three is wet, four is sooty, five and six look great.

Is it a coincidence that five and six had the carburetor that adjust correctly?
 

2025-02-04 Consulted Herb of C&H Cycle

Decided to talk to Herb Varin at C&H Cycle. He's an old skool tech very familiar with vintage bikes...

He was very nice, spent about an hour with me discussing what it might be. Herb suggested that I start first by lowering the fuel level in the float bowl by 2 mm. When I set the level, per service manual, it was using brass floats, not OEM. Not sure if this matters or not, probably not.

Herb's theory is that a little bit of fuel is dribbling into the Venturi and into the combustion chamber. Even though it's just a little bit, it is much more than the idle circuit provides,  rendering the circuit in operative.I think this is worth a try.

Additionally, I am going to replace the emulsifiers that wiredgeorge provided, the ones that had to be turned down to fit.


My theory is that fuel might be passing from the float bowl and over saturating the pilot jet circuit.

My plan of action is to perform the following steps.

1. Remove carbs
2. Lower fuel level 2 mm
3. Replace wiredgeorge brass with either Damien Ding or Keyster.. I have both available.
4. Drop the needles one clip as this bike has always run rich. Without the airbox, these plug should be running lean, and they are not.
5. Replace fuel inlet valves.
6. Hope for the best.

Fortunately, we have a storm coming in and this is work. I can do indoors.Persevere to persevere!

Thoughts and Ideas Welcomed!

The first time I disassembled and cleaned Christine's carburetors I noticed that one was allowing excess gasoline to pass through.
I thought it was due to a leak in the float valve, but in the end it turned out that the diaphragm had not been properly adjusted in place and had a fold that prevented the needle from fully lowering.

I'm not saying that's your problem, but don't rule out checking the position of the diaphragms of the carburetors that are failing you again¡¡¡

I few things in no particular order – just what pops into my head.Firstly:  It’s not necessary to have a “gauge” on each port for sync’ing.  1 Carb – 1 gauge.  Reduce the clutter!  Reduce the additional distractions.Although you discovered a Diaphragm that wasn’t positioned correctly; this would have no affect on the idle issues or cause excess fuel.  Regardless of Main-Needle height that the Diaphragm may have affected; no fuel can be delivered by the Emulsion-tube/Main needle until the throttle is opened considerably…enough to have the air velocity “Siphon” the fuel from the top of the E.-tube.   Fuel acquisition is completely different for the Idle and High speed.  Engine vacuum (“ Hg.) on the engine side of the throttle-plates is significant and quite different from the “Siphoning” affect (“ W.C.) on the air-filter side. It's the air velocity over the top of the emulsion-tube that draws "high-Speed" fuel. Focus on the inches Hg for your issues.Not sure what is meant by excess fuel “dribbling”.  All jets and porting are above the fuel-bowl level.  It’s the “inches HG” that draws fuel up an into the idle circuit.  Not gravity. No Vacuum – No fuel.The answer to a previous question regarding a “seal” for the emulsion-tube is: No.Are you using OEM or similar springs on your pilot-needles?  If the spring is too long/wrong gauge/too many coils it will feel like the idle needle is closing full stop when in fact the spring is stopping it from doing so.
In this case,  your “3.5 Turns” is going to have too much idle fuel being provided!   In this case the pilot needle will already be partially open, so adding 3.5 turns………you get the idea!    Lowering the fuel level 2mm?  I see the simple logic but very much doubt this will make any difference.  A tuned, idling engine, will suck the bowls dry and not give any indication of the lowering fuel level until the engine stumbles and quits, when the fuel runs out.Not a real concern at this time but something to consider next time you have the carbs off the engine:  www.kz1300.com/forum/bike-projects/3861-backfiring#29978 (or Search: intake leaks by scotch)A video cannot convey the subtle nuances of an idle but based on what I heard of your idle and transition – sounds good.
That’s all I got.  Back to my project.