Pilot Fuel Circuit - Unmasked

I pose a question that many of us are talking about. The answer to this question could be the revelation we've been waiting for as to why our mixture screw adjustments don't seem do a darn thing, even after we've thoroughly checked for air leaks, cleaned our carbs and adjusted our float levels.

THE QUESTION: "WHERE does the PILOT CIRCUIT draw its FUEL from?"

I know that the "pilot air jet", found under the diaphram - and most of the time located under a brass cover, is connected in name and function because when compressed air is forced into the pilot screw hole it comes out of that topside pilot air jet and the "tiny" hole found in the carb throat.

BUT, HOW IS THE PILOT CIRCUIT CONNECTED TO A FUEL SOURCE? If I knew, I could unclog it and get my baby back on the road. Instead she sits in the garage with LEAN carbs and WHITE PLUGS, and a pilot circuit that is unresponsive to any amount of turns from those pilot screws.

I'm telling you I can't get ANY bit of color on these plugs and the Float Bowl levels are correct. I'm actually considering up-ing them to see if that makes any difference. Right now all four levels are right to the top of the float bowl washers.

First one to answer correctly gets 20% off their next order from Chacal!

Just kidding Len!
Calm down Len, it was just a joke. No Len...put that axe down! NOOOOOoooooo!

 

does the 'pilot fuel jet' ring a bell ?

 

hehe, it cant be said any more straight forward than that can it

 

Thank you Polock! Sometimes the obvious eludes me. Immediatley after posting I was looking more closely at the carb diagram and noticed the dotted lines connecting the pilot circuit to the pilot fuel jet and said "Duh" to myself. However others are asking the same question so I don't feel so silly. It had to be asked because i honestly couldn't tell by testing. I tried blasting air into the passage and it doesn't come out of the pilot jet location. Does this mean it's clogged or will the air not come out there? I don't know how else to clean it because I boiled them in lemon juice for an hour and sprayed a whole bottle of carb cleaner in there.

 

hah. Wow, really? I am just as slow! haha.

 

Sounds clogged to me..... start cleaning

 

Actually, I don't think he'd mind at all, as long as you're the one paying the difference.

 

Ok, I tried this test on the pilot circuit.

TEST: With a broken Q-tip stuffed into the pilot air jet and my compressor nozzle placed securely into the pilot mixture screw passage (screw, spring, washer and o-ring taken out of course) I seemed to get a healthy blast of air out of the pilot fuel jet. Obviously the circuit is not clogged.

AFTER THOUGHT: My pilot fuel jet is the stock #40, but the PO installed a massive #118 Main Fuel Jet. Could this be leading to a lack of richness when the pilot mixture screw is opened up. Is the #40 too small for the job now considering the extra fuel being drawn by the main fuel jet?

 

Have you checked for proper placement of your idle mixture screw Orings and washers?

Should be O ring in the hole first, then washer, then spring, them screw.

I think that might be my issue if it isn't clogged passages, so I am checking that tomorrow.

 

Clean your pilot fuel circuit, starting from the jet on upwards, until carb cleaner sprayed into that passage emerges from port up on the top side of the carb. And then reverse things, spray the cleaner through the top port, and it should come out the bottom (will also come out of the pilot air jet port, too). Tiny wires are the answer (like in our HCP951 cleaning wires set); boiling in lemon juice cleans the aluminum surfaces, but does very little to get 25+ years of hardened fuel gunk loose and removed.....that takes mechanical action.

But I bet those carbs smell zestfully clean..........

 

P.S. you may soon qualify for a T-shirt...........


http://www.xjbikes.com/Forums/viewtopic ... tml#154359

 

Haha! Thanks for the cleaning advice Len. I also can't wait for that T-shirt! And boiled lemon juice doesn't smell as nice as one would think. It's actually pretty nasty smelling to be quite honest!

Dpawl- Thanks for looking out for my Mixture screw ordering. Yes, they are in the right order, however, last night I found an extra washer clinging to the bottom of a mixture screw between the spring and screw. It was pressed on there good because it blended in with the screw. Was either done by the PO or me during my first carb reassembly! But here's one for you. On Carbs 1-4 the mixture screws bottom out with the flat head slots in this orientation: Horizontal - Horizontal - Horizontal - Vertical. Whats up with #4?

 

The best way to assure the Pilot Fuel and Air Passages are clean is to FLUSH them.

You need a Syringe.
One like this. (Although, having the Large and Small one is GREAT)



Shoot some clean Carb Cleaner into a cleaned, glass container.
Squeeze the Syringe and draw-up a couple of ounces of Carb Cleaner.
Place the "Nozzle" into the Pilot FUEL Jet Port --> Jet REMOVED!
Squeeze Bulb and force Cleaner through Passages.

Flushing Pilot FUEL Jet orifice up through Carb Body should have Cleaner exiting the Pilot AIR Jet and the Pilot Mixture Port.

Flushing the Pilot AIR Jet orifice through the Carb Body should have Cleaner exiting Pilot FUEL Jet Port and Pilot Mixture Screw Hole.

Main AIR Passage Flush:

Flushing Main AIR Jet Port through Carb Body should get Clean Carb Fluid exiting Main AIR Port near bottom of Center Main Fuel Supply Bore. --> Brass Emulsion Tube Removed.

Flushing Fuel Bowl >> Warning: Eye Hazard <<>>!!!

Flush the "Well" under slight pressure with the Nozzle inserted into the Top of the Well opening.

Flush Siphon Tube --> (After "Probing" with Tool or Correct Gauge Wire or Guitar String)

Slip Nozzle OVER Siphon Tube. "Seat" Nozzle-end against Carb Body and Squeeze Cleaner through Passage with Enrichment Valve OPEN or Removed.

 

Palmer, one of my screws sits further in than the other 3, don't know why, probably just a different threading depth?

The screw were all exact same size.

Rick, I KNEW there was another way instead of the ghetto cleaner straw.
Gonna have to look for a good set of bulbs now

 

I think you can get such bulbs at a pharmacy - used for sucking the gubbins from baby's nose! :lol: :lol:

 

That, and ear wax out after it gets flushed with, say, hydrogen peroxide

 

Let me get this straight... FOUR holes all together, right?

Fuel IN pilot jet inside bowl.
Fuel OUT inside throat.
Air IN via pilot air jet under hat.
Air OUT via hole inside throat.

Mixture screw adjusts airflow, increasing fuel flow.

Yes/No?

One would assume the air passages aren't my problem - more than likely the fuel side of things.
Anyone know how many 'bends' they make inside the casting?

 

Perhaps fuel and air flow, perhaps? Maybe?


How many twists and turns? At least three.

 

Well I heard someone on here, they adjust AIRFLOW, and the resulting AIRFLOW increases the fuel flow?

Is that wrong/right?

 

You might have missed out on the other, follow-up thread...........

 

Ugh, typical Len, make me work for it...



So going by that... air AND fuel, in the SAME passage... ONE air in, ONE fuel in, ONE main outlet, yet the BYPASS holes allow it to flow when the throttle plate opens.

SO!

With the plate nearly closed. Bypass holes are shut off mainly.

Running of straight mixture screw outlet.

Open the throttle a bit - and the additional 'bypass' holes allow more fuel out of the pilot circuit. As well as air...?

Anyway, So if you start off with a bench sync that has the throttle plates TOO FAR OPEN, then the colortune will be seeing fuel out of the bypass holes too...

Under the assumption the only fuel getting in the motor at IDLE is from the output of the screw itself, and the bypass holes assist in getting off idle to transition to higher RPMs and the MAIN.

So, if my bike idles like piss when I start it up cold... it's not getting enough fuel from my screw output itself. But if I crack the throttle, just a tad, it starts to react, but not well. Thus, I am coming to the conclusing my circuit between my screw and my bypass is nearly completely clogged, and between the jets and the bypass is partially clogged.

Wow. Damn you Len. Make me think.

Did I mention I love you?

Er, damn you! lol.

 

Make a Fluid-Separating Vacuum-Bottle.
Hook-up the Bottle Vacuum Line to your Shop-Vac with some Duct Tape.
Hole the Probe Vacuum Line to the Pilot Mixture Orifices and see if you draw Fuel from the Fuel Bowls into the Vacuum Bottle.

Peanut Butter Jar.
Vinyl Hose.
Epoxy.

 

Top hoses: one to atmosphere, one to shop vac.

Side hose - to pilot screw hole? without a screw?

Seems like a lot of work but I can see how it could help.

Or is it two hoses on top to air jet and pilot screw hole?

<--confuzzled.

 

Doug, please! What's love got to do with it?


Although, following your "stream of conciousness" thoughts, you're okay up to the point where you talk about going from bench synch to colortuning, because..........it shouldn't be done that way.

Bench synch is just an initial way of setting the carbs up so they all have pretty much equal throttle shaft opening, and, BARE MINIMUM openings at that.

That method gives you the BEST CHANCE for allowing the engine to be started and running, even if poorly.

The VERY NEXT STEP IN THE PROCESS is to SYNCH THE ENGINE----not the "carbs", but the ENGINE----via the proper procedures.

ONCE THE ENGINE IS SYNCHED, only then do you start fiddling with the colortune, mixture screws, etc......which, as you fiddle and adjust, you should re-synch the engine after each adjustment. It's what the call a "nested Do-Loop" in computer coding, or an "iteration" in technical terms, or "do this, then that, then this again, then THAT again, wash-rinse-repeat" on the streets of Salem......


In fact, one of the confusing aspects is referring to the setting of the throttle blades equally on the bench as a "bench SYNCH".....technically, it is the proper terminology (because we are setting the throttle blades equally, i.e. "in synch with each other"), but when we get to the RUNNING SYNCH, then by design and action we're turning the synch screws, which just so happen to be on the carbs, and setting different butterfly valves to DIFFERENT OPENINGS........only in this way can we get THE ENGINE "IN SYNCH", which means getting an equal vacuum draw from all of the cylinders.

The "synch" part always means "in equality, or in harmony" with each other, but while on the bench, it's the equall-ness of the throttle blade openings and mixture screw settings that is at issue, while on the engine, it is the equall-ness of the vacuum signal from each cylinder, and getting the vacuum signals equalized means we're going to be getting different mixture screw settings and different throttle blade openings on each carb (likely), as we attempt to compensate for ALL other factors which can influence cylinder vacuum pull (cylinder and ring conditions, valve seat conditions, valve clearance conditions, etc.).

Words get in the way, sometimes. So does lack of knowledge of what the real world, mechanically speaking, is all about. So does hubris, that whole "I know better than anyone else" mentality.

Wisdom sounds foolish to fools..........

 

Wasn't trying to say go straight from bench sync to colortune.

Merely stating if you had a bench sync with the bypass holes exposed, a colortune would show rich, always, due to the bypass holes. Even if the pilot screw was shut completely.

That's all!

I use the colortune to determine whether I am even FIRING in that cylinder.

As you know - my pilot circuit is clogged to _____.

So when I dropped the colortune in, with a fresh sync - every cylinder @ 2.5 turns out was barely firing at all, and missing a LOT.

Hence, the 6 turns out before it fires evenly every time.

You know where I am going...

Cleaning those suckers tomorrow, re-bench sync, with business card instead of paper clip this time. Once I am sure of the bench sync and cleanliness of my passages, I will reinstall and try a real sync, then colortune and see where I am at. If I pass 4 turns out... umma be pissed!

 

You have a way of twisting words, Len.
My manual doesn't mention 'engine synchronization', but it does have a section headed 'carburettor synchronization'

 

Nice try Wiz. But tell me you can do better than that.

Please!

Tell me you can do better than that.


http://dictionary.reference.com/browse/synchronization

I suppose we need to revisit Synchronization 101 again? That didn't go over so well last time?

Perhaps the same fellow who wrote that passage in the manual about using the YICS Port Blanking Tool when performing a synchronization used the word "carburetor synchronization"?

Maybe he got both wrong. Maybe he's batting 50%? You didn't believe him then, why now?


So please tell me----and everyone else----which of the many definitions of "synchronization" from the reference above describes what the process called "synchronization" in Yamaha-speak deals with.

Does it apply to the 4 carburators themselves, their settings as with the bench synch, or does it refer to something else?


* Are all the butterflies set to "coincide, indicate the same, move, operate, work, etc. at the same rate and exactly together; to occur at the same time, be simultaneous; to operate in unison" during this "synchronization" process?

* Are all the pilot mixture screws set to "coincide, indicate the same, move, operate, work, etc. at the same rate and exactly together; to occur at the same time, be simultaneous; to operate in unison" during this "synchronization" process?

* Or, are all the carbs adjusted differently from each other so that the EACH CYLINDER PRODUCES THE SAME VACUUM DRAW? Is that anything like "indicate the same; work at the same rate and exactly together; to operate in unison"?

I have taken liberty to italicize, underline, and/or bold the pertinent issues for your reflection and review.

So go ahead, take your time, don't rush. So much depends on your answer.

 

Is it haemorrhoids Len?

 

You make adjustments to the Throttle Plates at the Carburetors to Synchronize the Engine Performance.
What it is that you are doing is Balancing the Manifold Vacuums of 4 Carbs to ALL be the same.

Since the Condition of each Cylinder will determine it's Vacuum efficiency; the Manifold vacuums present while the Engine is running might vary.
In fact they do.
We correct for that with the Running Vacuum Sync.

The strength of Manifold Vacuum will depend on:
Valve Timing and Condition.
Piston Rings Condition
Any AIR Leakage at the Manifold
Throttle Plate Position

 

Thanks Rick! I recall you mentioning a baby syringe in another post- so when we were at the hospital with our newborn I swiped a couple from our post-pardom room. The nurses encouraged us to take anything that isn't bolted down...so I did! Right now the pilot screws have to be at least 5-6 turns out to change engine idle. Still don't have much color on plugs but it idles much smoother.

I will give the bulb-cleaning a go and let you know how she runs afterwards!

 

careful with those baby syringes. I got one at CVS and the carb cleaner ate a hole right through before I could finish using it.

 

I used the ear-wax removal bulb, soft rubber. Ate right through it.

I think a hard plastic syringe, like a real syringe, would hold up.

Plus, I'd probably use gas to force the stuff through, then flush with carb cleaner next time.

I have a funny feeling that my bypass holes are still a problem.
The one thing I did not try was to plug the fuel jet, air jet (with syringe) close the pilot screw, and pressurize. That's the next try... ugh.

Wednesday for me : Pull carbs again.
Pressurize pilot circuit with ONLY bypass holes open. Then flush whole circuit. Bench sync / running sync, see where I am @ with colortune.

Wiz, if you want to slap a sarcastic reply out in a thread because you just got corrected on the fact that you sync an engine, not the carbs... maybe try spelling hemorrhoids right next time?

 

Soak the carbs in Pinesol over night and all of the crap will blow out easily.I have done this many times and have had great results.The best pat is that it will not hurt any rubber/plastic parts or gaskets if you miss one.

 

I've done the overnight Pinesol soak and then boiled them in lemon juice; they are still not fully cleared out however. The Pinesol was great at removing dirt/grime but didn't strip off the old gas and varnish buildup. Danno is correct though, it doesn't harm rubber parts!

 

Dpawl, your spelling is an American alternative.
There is however, a more serious issue here, which is that you will post enough nonsense to achieve the rank of XJ wizard, without being able to fix your own POS bike, let alone assist other members.

 

Looks who's talking...........Mr. Helpful himself.

 

Guitar strings, (G and D) Work pretty well for unclogging small passages in your carbs btw!!
I've always got some handy
Just snip off the tiny part you're supposed to thread through the eyes.
-SLkid

 

Other than daring to suggest that in some cases the YICS tool might not make a great deal of difference to the sync', where else do you think I am unhelpful?

 

Dpawl... you have unfortunately been caught in Wizard and Chacal's ongoing YICS Synchronization Battle. "Two Men Enter- One Man Wins. Two Men Enter- One Man Wins!"

 

hmmm...... 8O :? :roll:

 

+1 on guitar strings

 

E works great too... even smaller.

Wiz. Just about every thing you post is nonsense.

Must be 'lay terms'. haha.

Palmer - Trust Chacal with your life.

Trust Wiz with... who am I kidding. Nothing.

POS bike eh?

You don't even care to list yours in your sig.

Do you even HAVEEE a bike? Or is it a big wheel?

 

Apparently it isn't about YICS, but marketing & I don't have anything to sell.

 

Once again- you boggle my mind.

What am I trying to sell? Really now.

I think you are just ornery because you are a Honda fan

 

Is everything under control?

 

LOL... we're good Rick!

Wiz just likes to talk smack about Len, and I am not a fan of that.

Anyway, how's the knee doing? I can't wait to show you the bike...

 

Palmer650,

I'm having what appears to be the same issue you are right now. Have you gotten any closer to a resolution? I'm getting a bit frustrated with mine... I just can't get my colortune to show any yellow, even with the mixture screws almost all the way out. Checked for air leaks by spraying Gumout around carb joints etc. and can't find any. (That's how I initially found that my throttle plate shaft seals were leaking - replaced 'em). Carbs have been thoroughly cleaned, & rebuilt. I'm obviously doing something wrong here - but what?! Too much air / not enough fuel.

'82 XJ650J

 

Xjamien...I can't say for sure yet, but I'm thinking it's 2 different factors adding to the problem. 1st... my fuel jets are not correct #118 and #40. I bet if I beefed up my pilot fuel jet to a 42 i would see some color since that main jet is so stinkin big. 2nd... I have to flush the pilot fuel circuit out with a bulb of carb cleaner, boiling lemon juice, brake cleaner, etc. It's not completely clogged but is definitely not 100%. I'm going to give the flushing procedure a go this weekend and see if it helps.

I added more fuel to the #1 bowl by adjusting my float level and it immediately colored up the spark plug. However... the float levels have to be flooding or close to flooding the carbs out before this actually works so it's not a fix to say the least. But a higher fuel level does make it run richer. Hehe!

 

How do know 100% that the entire circut is 100% clean??? I have sprayed cleaner through mine and if i put my finger over the jet hole it sprays out the tiny hole by the butterfly!!!
I am ordering my new main jets, pilot jets and colortune today. I think one more clean-up and needle and seat polish and a bunch of tuning and i will be safe to ride!!!
I'm just wondering about the pilot??? i have mine 3.5-4 out now????

 

I wouldn't think your main fuel jet would have anything to do with the idle mixture. Anyway, if your jet is 118 instead of 110, it would be letting through MORE fuel - which wouldn't make you run lean.

Yeah, I did the lemon juice thing, followed by a hot water wash and a jet spray Gumout carb cleaner.

It's gotta be either too much air, or too little fuel. I don't know, I guess if I don't have an air leak, I must have a partial clog in the pilot fuel circuit somewhere. Guess I'll have to check 'em AGAIN! Pullin' 'em off tonight...