Adjusting air/fuel ratio

Hello everyone,
I need some advice regarding how to set the air/fuel ratio at idle. Everything on my XJ550 is stock so I don't see the need to rejet or do anything else. So far I have heard of
1. Tuning by ear - with detractors claiming that it can never be accurate enough. Besides this is my first 4 cylinder bike and I dont know what I should be hearing.
2. Buy a Color tune. These cost 50 bucks and I am not sure that it doesnt suffer from the same problem as above. How blue should blue be? Also it costs 60$. Ok lets see.
3. Gas analyzer with a Dyno ... yeah. whatever.

Here is my idea. You can get a O2 sensor for a car for cheap off ebay. Stick this in the tail pipe and hook it up to a volmeter (connect the heater wires to the battery) and turn the air screws till you get the correct reading. I know it wont be 100% accurate since two cylinders share an exhaust but I am thinking its better than tuning by ear? Anybody done this?

 

pull the plugs, clean & adjust, or get new set.
run the bike for 20 miles at all speeds.
pull the plugs & post a clear close up picture with the plugs on white paper & the plugs numbered, we will tell you what you need to do with your mixtures.
see you later. Wiz.

 

plug chopping is cheap, easy, accurate enough to make the bike run beautifully and efficiently.

blue paper will work also.

 

Colortune is a great tool to get you a close starting point. I have one and it is great. But as Wiz and Zookie said plug chops are the way to fine tune.

 

We're assuming you have already "bench sync'ed" them? Next step is vacuum balancing with YICS blocked; then colortune. Then plug reading.

 

Look at my gallery at the bottle synch contraption I rigged up.
Its way cheaper than meters and can detect the slightest imbalance in your carb synch screws.

Once you know your valves are in spec you should balance the carb vacuums.

My bike would die when I twisted the throttle. A minutes with the magic bottles and it was a totally different bike. It will now throw me off the back if I am not hanging on to the grips.

 

Should there be two of these contraptions to do the four carbs at once or do you suggest to do a pair at a time?

 

The procedure is two at a time.

Do 3-4
Do 1-2
Do 2-3

The left and right adjustment screws balance PAIRS and not individual carbs.

The center adjustment screw adjust the 1-2 pair to the 3-4 pair.

Clarification: The rightmost screw adjusts #4. #3 is not adjustable.

The leftmost screw balances 1 to 2.

The center screw balances the two pairs.

 

I like that, Half Century, very concise.

 

Thanks for the kind words Mr. Wizard.

 

I bench syncd them "visually". I have always read valves need to be adjusted with some even insisting that the tuning is worthless without the valve adjustment. Is that true? why is it necessary? Also how can the plug chops be more accurate than the color tune or oxygen meter? it seems so subjective AND time consuming. There are some folks that claim your good settings are a few degrees of each other. My plugs look the nice chocolate brown like it shows in the pictures and i haven't done any tuning - just set everything at 3 turns out. BUT, I will post the pictures and tell me what you think. Also I saw some guy on this forum who hooked up 4 tubes with a cross joint and I don't see why 2 at a time is better. we need to make 4 quantities the same, we can follow the same procedure that half century suggested while watching the level on all 4 carbs. But i am glad to know i can sync before setting fuel mixture. I will do that. I will set the valves another time I think.

 

you can hook up 4 meters / jars, but the 2 at a time method is all you need, I do mine with 1 gauge, (see RickCoMatic, old school method)
Plug chopping is soooo easy & it shows you what is going on in each pot, but you have to be in the ball park to start with, so that is, bench sync' & vac' sync' then chop & yes very small degrees of turn produce major results. Get a protractor & see how much 2 deg of rotation actualy is.

 

The tubes only contraption can easily allow the liquid to get sucked INTO the vacuum intakes.

The bottle thingy can be set up to never allow the display liquid to enter an intake.

I have one of the meters and you would be lucky to get the meter to be 5% repeatable. The bottles tell when the intakes are EXACTLY matched. With the bottles you can rev the engine and see the balance at ANY RPM level.

 

Yes, it's true. It's necessary because the valve clearances affect valve timing as well as how long each valve is actually open for. Tuning your carbs is a matter of trying to match each cylinder to the other. You can't DO THAT if the cylinders are operating with different valve timing and duration. These four cylinder bikes (especially the 550s) have some pretty small diameter cylinders and they need to be as evenly matched as possible in their ability to move air in and out before trying to adjust the mixture of the fuel in that air. The other reason it's important is that most of us have taken over bikes with some miles on them, and in all likelyhood a valve adjustment has never been done. Trying to synch freshly cleaned carbs on a motor with 10K or 20K or 30K miles on it and no valve adjustment is just a recipe for frustration. It can't be got right.

 

well the valves should be adjusted but to not sync the carbs just because you didn't set the valves just don't make sence
it's far from useless, you might have to sync after carb work just to get a reliable idle, that said, after you adjust the valves your going to sync again, no big deal
sync and mixture is a back and forth thing the mixture will change the sync
that YICS tool is a whole nother story

 

valves that are tight and being held open could throw off carb sinc.

 

so could a lot of things but does that mean it's not worth doing ?
the man says he has a descent running bike now and wants to tweek the carbs
i see nothing wrong with sync'ing them without setting the valves first
as long as he knows he should check the valves
if he can't get them dialed in or has other tight valve symptoms then check the lash

 

From my experience I know that some of my valves were tight.
I synched the carbs and the bike ran incredibly better. Before synching the bike would die when throttle was applied. After synching it accerates like a scalded dog when you twist the throttle all the way.

Yes, go ahead and synch your carbs until you can check the valves.

Its better than having unchecked valves and unsynched carbs.

 

Yes, what Pollock and others say is true, you CAN synch and Colortune without first checking/setting your valves, but if your synch-and-tune results in a much better running bike (likely) AND IF THAT MAKES YOU LESS MOTIVATED TO CHECK/ADJUST THE VALVES-----well, that's where your troubles really begin (won the battle, lost the war type of thing.....).

The key to understanding this whole issue begins with understanding that you DON'T "synch carbs".........this poor use of words leads to a mountain of mis-understanding of what it is that you're actually trying to accomplish.

The word "synchronization" means "getting things equalized" between various component pieces. Are you setting each individual carb to the exact same specs?----the same idle mixture screw setting, the same throttle valve (butterfly) opening during this procedure?

NO, YOU'RE NOT. You will have different settings on all four carbs when you're done with the procedure.

WHY?

Because YOU'RE NOT "SYNCHING" THE CARBS!

You're "synching" the engine, or, to be more precise, you're synching the POWER OUTPUT OF EACH CYLINDER TO EACH OTHER.

So that each cylinder provides the SAME (not the maximum) POWER OUTPUT.

You measure the "sameness" of power output via how much vacuum pull each cylinder develops. This is why the synch procedure measures cylinder vacuum rather than a carb-specific issue (such as rate of fuel flow, air flow through the carb, etc. Notice how the vacuum draw is measured DOWNSTREAM of the carbs...........).

You can ADJUST how much power each cylinder outputs (and thus how much vacuum each cylinder draws) via a number of methods, here's a few that come to mind:

- you can bore out a single cylinder, giving it a bigger displacement, thus more power output.

- you could re-ring an individual cylinder to give it a better seal and thus more compression.

- you could ADJUST THE VALVE OPENINGS (or timing, and the two are related, as Fitz points out above) on an individual cylinder to be more or less than on others, thus affecting how much air/fuel is drawn into that cylinder, and how much compression that cylinder builds.

- YOU CAN FIDDLE WTH THE CARB MIXTURE SETTINGS AND BUTTERFLY OPENINGS TO "CHOKE DOWN" THE STRONGEST CYLINDERS.

Note the very important issue in the last statement above: you can adjust the carb settings to "starve" the best cylinders down to the performance of the lowest-performing cylinder......and thus can "equalize" (synch) the output of each cylinder DOWN TO THAT LOWEST-COMMON-DENOMINATOR cylinder.

You know, you COULD actually set all the carbs to be exactly equal in their mixture screw settings and throttle blade openings, and then mess around with the individual intake and exhuast valve opening settings (re-shimming) until all cylinders matched each other in power output (vacuum draw), too......

That would be silly, not to mention quite time consuming.

THAT'S why the factory (or any engine builder/tuner) says to get all the valve clearances set to spec, first, and then do the "fine-tuning" adjustments via the carb adjustments.

The whole issue/question of adjusting the carbs before or rather than adjusting valves really comes about because of the mis-use of the phrase "CARB synch" since, in reality, there ain't no such procedure!! But people hear those words and naturally think to themselves that the adjustment of the CARBS is the be-all and end-all of the SYNCH process, when in reality, IT IS THE FINAL STEP IN THE ENGINE-SYNCH PROCESS!!!!

Also, on these engines, over time, as wear occurs in the valvetrain, the valves LOSE clearance, and thus become "tighter" and spend more time in contact with the actual cam lobe.

On the intake side, a tighter (less clearance) cam-to-shim clearance gives you more lift, and more valve "open time" duration.

On the exhaust side, it results in exactly the same things.

AND SINCE THE EXHAUST VALVE DEPENDS ON A PROPER AMOUNT OF "ON-THE-VALVE-SEAT TIME" FOR COOLING, having a "too tight" exhaust valve means the exhaust valve doesn't get enough seat (fully closed) time on the valve seat in the cylinder head, and thus runs much hotter than designed.

And that slowly burns the exhaust valve.

And that results in a much more expensive fix in the future, or, if it's just a wee bit burned, much less performance from that/those cylinders, which means then next time you "synch", you're going to be bringing all the other cylinders DOWN in performance to the one with the slightly burned exhaust valve.......

Yamaha motors are pretty bullet-proof little devices. Best to keep them that way through following proper maintenance procedures.

Just my 2-cents. Like the old Fram oil filter commercials said:

"You can pay me now, or you can pay me (a lot more) later....."

 

I built the YICS tool . I also built a simplified manometer as shown here.
http://img99.imageshack.us/img99/9916/manometer6ot.jpg

The manometer doesn't have to be 5 miles long to avoid risk of sucking fluid into the engine. The tube that connects above the engine oil level desensitizes the manometer. Yes it still works. And as you get close to equalizing the pressure between the two intakes, we can pinch this to get more sensitivity.


With the YICS though i couldn't get the nylon reinforced kind. Just a rubber vacuum tube. How hot does it really get there. am i at risk of having molten rubber in there?

 

chacal,

thanks for that detail breakdown. I was hoping for someone to explain like that. I will look into doing that next. This is my first bike and I have ridden it 5 times each time around my block. I have spent about 200$ in parts and countless hours in labor . All of this started with a quest to make it start easier. so far, put new m2c boots. cleaned carbs, drilled out one air screw. unfreezed the drain plugs. built yics and manometer. I fixed the turn signals, by replacing the cap and removing the auto off module. Put a new fuse box. I still have a starting problem. I think i have a fuel supply problem. bike is only running on prime. So from where i began, i have one less electrical problem and one more fuel supply problem. Oh yes I also have a season problem - I have to wait till April to ride. So I would like to fix the real problems first. Sorry if i sound whiny. I think i enjoy this. I enjoy fixing problems. Oh btw, do you have drain screws and starter brushes?

 

Answers:

a) Really hot!

b) Yes, you can melt the rubber seals on the YICS tool if you leave it in there for any extended length of time! Remove it frequently, a synch procedure (without any in-between colortuning) shouldn't take over 3-5 minutes.

 

Hananiel, send me a PM and I'll get you some prices.....and please remind me again what year and model bike you have!

 

So I can use my rubber hose as long as i don't run the engine for more than 3 minutes at a time or is this with a nylon reinforced hose or is there no difference between the nylon reinforced and my rubber hose?
thanks,
hananiel

 

I'm not sure that I understand the question..........the YICS tool has small rubber seals that expand when the took is operated, thus sealing off the YICS chamber within the cylinder head before adjusting the carb synch screws. I'm not sure what you are referring to when you talk about "the difference between the nylon reinforced and my rubber hose?"

What you have pictured in your imageshack image is the mamometer. not a YICS tool....???? For that device, regular rubber tubing is just fine.

 

Hi hananiel, looking at your pic of your manometer, if you intend to connect the clear plastic to the vac' ports on the carb' boots, it won't work, it gets too hot for plastic tube, you need at least the first 6 inches to be vac' line.

 

Wizard,
That wasnt mine. I was pointing to another forum somewhere and that is someone else's work. I was trying to post some pictures but I couldnt figure out how to. I attached a file but i dont know what became of it. Also the carb holder itself is rubber right?

Chacal,
My question was, I built my own. The plans ask for a nylon reinforced gas line, but I couldnt get that so I just put a vacuum line that I could find that was rubber only - not nylon reinforced. Some one (I think Ricomatic) actually suggested putting a dowel rod of the right diameter and that the point was to block this hole that is the YICS gallery. I don't know why the plans have such exacting specs. I do see the point of flexible heat resistant material forming a better seal. I understand it, but given the gas line of the correct OD/ID is so hard to find, there must be some other way or an alternative.
-Hananiel

 

Yeh, the carb boots are rubber, not poly pipe.

 

Now, when I go to sync the carbs, where do I connect my tool to?? Thats the only things I cant seem to figure out