How did Yamaha set pilot screws from new?

I've read lots of posts about setting mixture screws and using colourtunes, but wonder what Yamaha actually did when the bikes were new?

Has anyone any ideas?

 

I believe I read somewhere about exhaust gas sensors.

 

I am sure they tuned the bikes for emissions and economy, not performance.

Funny thing is, Rosie is tuned for performance and SWMBO is getting 48MPG, and she likes the throttle!

Rosie is colortuned just below the yellow, into the light purple.

 

Take a close look at the bottom of your exhaust head pipes. If they're stock pipes, you will find a little 10mm bolt head on the bottom of each. That is the EGA port plug.

Yamaha tuned to specific EGA readings at (high- 1500rpm) idle and 5000 rpm.
I have a copy of the Yamaha EGA manual, it's pretty interesting reading.

We've replaced the EGA with the ColorTune. Nowhere near as precise, I'm sure, but a lot more cost efficient.

 

I just drilled the plugs out of mine and wondered the same thing. What Fitz just said must be the reason that #1-3 were about 2 turns out and#4 was 1.25 turns out. I set them at 2.75 turns out.

 

Really? On the assembly line, motor in frame, they oiled up and ran the engine inside the factory, then after fiddling with the sync and 4 pilots, with the frame in the way, they installed the brass caps?

Or did they do this in an engine department, matching carb racks to engines- - I don't know, just asking- - I'd also like to know how they loaded the motor into the frame ( 2 Sumo wrestlers and 4 Ninjas)

 

You bet they fire them up in the factory.

Hard to imagine a tech connecting the ega to the pipes and straddling the bike on the line. Much more likely the carbs and engine are set up before they go to the line or even the carbs alone done in a test fixture before meeting the engine.

It's a really big issue if you find you have a defective carburetor after the motorcycle is assembled. Not so bad if you find out before the carb ever meets the engine.

 

That's exactly why. Factory settings on my "virgin" rack of 550 carbs had the #1 and #4 about 1/2 turn further out than #2 and #3.

 

after pulling my caps i found the pilots set between 1 1/2 turn to 4 turns out.
of course that was just after buying the bike and finding this site.

what a diff after i reset to 2.5 and a synq. i'll bet thats the real reason
the po sold it...no power.

i bet he would cry now!

 

Some carburetor kits come with replacement plugs.

Just because the screws are plugged doesn't mean they're at the factory setting.

 

I re-synced the carbs with the "yics stick" and turned the screws out to 3 turns. Much better as far as holding idle when warmed up. Also better cold starting results ,no stalling.
Thanks to all for sharing all the info!

 

The Plugs in a New Bike were most likely put there at the Dealership.
There was a Regulation about that which varied State to State.

Even Bikes that were set-up at the Factory had the Plugs removed and the Mixtures re-set a bit more Rich than they were when shipped due to so many complaints from new owners about the way the Bike ran after being set-up to the EPA Specs.

When the EGA Machines were transferred over to become the responsibility of the Dealerships rather than the Factory; most Dealerships quit using the Machine set-up and the "Turn-Out from Bottom-Out" method became the rule.

The EPA Set-up done on the Machine caused the Bikes to begin regular visits to the Shop because the EPA Requirement reduced the Supplemental Pilot Mixture Ratio to where the Machine stumbled and didn't "Get-going" very well.

Having abandoned the Machine, the Dealerships adopted a Universal Preset that appears as a Spec in Manuals which released the Information.
2-1/2 Turns Out from Bottom was universally adopted as "The Sweet Spot" for finding where the Bike would Idle and keep the Machine compliant with Regulations for ALL the States except California.

California Bikes often had additional "Plumbing" added to recirculate exhaust gases or add fresh air to the exhaust gases by employing a "Coasting Circuit".

Without the aid of the popular ColorTune Plug; it became commonplace to adjust the Pilot Mixtures "By Ear".
Adjusting the Mixture to achieve a steady and slightly elevated Idle Speed and Tuning to achieve a Mixture that wouldn't Backfire or Wait for Main Jet Supplied Fuel became the Benchmark for Post EGA Machine Set-up's ... "Shooting for >> "On the Rich Side" rather than Lean, to protect the Bike, Tech and Dealership from any consequences that might occur from a Mixture that was set-up too Lean.

The ColorTune Plug the relaxed enforcement of emissions ... is most States ... allows the Tuner to "Find" the Sweet Spot and make an Educated Guess where the "Best NON-critically Lean Mixture" has been achieved.

THAT setting found by the ColorTune Plug will vary a good deal from Bike to Bike ... depending on the Condition of the Engine's Mechanical State, the Cleaniness of the Carbs, and the level of Intake Air being introduced to the Cylinder and is regulated by the sizes of both the Pilot AIR Jet and Pilot FUEL Jet found on the Machine being tuned.

Until the Pilot FUEL Jet and AIR Jets sizes are verified to be correct; using a Ball Park Pre-Set value ... such as: "Two and a half turns out from the bottom" ... will place you in the Ball Park.

But the Ball Park you are in isn't the one the ballgame is being played at.

 

that helps explain things a little.

how does one tune by ear though? ( yes i know-by hearing)

i've been using plug color as my indicator of lean/rich conditions but if i
do it by hearing too then it could be that much more accurate.

 

Search this site for it. Rick has an excellent write-up

 

Tuning by ear is something learned from years of experience and NOT a "more accurate" method by any stretch.

I've yet to see a "tuned by ear" 4-cylinder that runs anywhere nearly as well as one tuned using even our less-accurate-than-original instrumentation.

Frankly, I can get my Norton just as close using either method, but on it you unplug one cylinder and just set one at a time. I'm sure if you could do that with an XJ it might be possible; but speaking as someone with 40+ years experience "tuning by ear" it ain't gonna happen on a busy 4-cylinder.

 

I can assure you that almost all Xj's delivered in the early to mid 80's had the carbs worked on at the dealership prior to delivery. Having worked at a dealership at that time I remember the grin on the owners face because of all the warranty work that Yamaha paid for to clean the carbs. It seems that Yamaha used some type of fire retardant in the fuel system before shipping that absolutely gummed the carbs up terribly. They all had to be pulled and cleaned.

 

It wasn't just fire retardant, they had a heck of a time with dried fuel deposits as well as good old fashioned RUST.

There were a number of "overlapping" tech bulletins pertaining to the problem, as they struggled to find a quick, easy answer. (On-bike flushing, etc.) There wasn't one...