Who's Tweaking & What Are You Doing? Dialed-IN Check!

I did the Adirondack Northway, the New York State Thruway and the Mass Pike ... all of it!

Yanked the plugs and eyeballed 'em after and all-afternoon jaunt at highway speed.

Although I had thought the Colortune had me just about Purr-fect ... I found my #-3 Plug "Juaaa-est" a little too clean for it own good.

I had Summer-in-the-sun -- Tan on 1, 2 and 4

So, I added about 2-thousandths Out on the 1, 2, and 4 Carb ... and, a little more than that on 3.

The effect was I got took the "Crispness" out of WOT and Mellowed-out the ride to Cruiser. (I took the Sportbike out of her.)

Now, I have strong pull in all the gears. A little less "Growl" at the high end of the tach and appreciably less "Engine Braking" ...

She likes to Coast and Cruise now. I'm happy with that! But, I really dig being able to get out of the hole FAST. Now, it's not as quick ... but, she really likes being up around 75 ~ 80 mph and running there like an Atomic Clock!

 

I'm not even close to being dialed in!!!

I've put about 5000 miles on my XJ since June, having only changed the oil and final drive fluid, bled brakes, cut out exhaust baffles, remove luggage, and clean the paint off of her.
I have no tach so I cant tell you when she gets up and goes (other than Mid-to-low growl through very angry high pitched whine)!

I love her all the same!!!

 

just reinstalled freshly cleaned carbs. solved most of my problems but still running pretty lean (too much.) checked float levels, and they are about a half inch from the top of the float bowl. this is low, so hopefully fixing this this weekend will solve some of my woes. have all the mixture screws at 3 turns out. idle isn't hanging high anymore, but still have popping in the pipes, and its still getting warm.

also ordered new airbox boot to replace the one that is hanging on by a thread...if its even hanging on any more.

so i guess i'm almost to fine tuning.

 

I would say almost dialed in,,,,,,,bike started this spring out with #7nkg's running dark. these are hotter than stock an should be whiter,,,,,the bike was hard to shift rpm's fell hard an she pulled hard when you open the throttle back up. the sweet spot for me is cruising at speed with the vibs as low as possible at a speed as high as possible without vibs don't mistake this for high speed passes.60-70-80 all have there state of tune,,,, this is not for the faint of heart,,,,an this is a quest for knowledge as much as a bike that will carry me all day without torturing me with vibs,,,,I'm looking into getting back on the road again,,,,I've had the HD lead sled in the past,,,,a bmw is to much $ for me right now,,,,I had my doubt's I really wanted to go this route the best rides I remember where country roads going west at a pace that really wasn't that fast,,,,sport-touring

I did not do the air screws over last winter 1st mistake,,,,,an the tuner in me went back in...I still could not get her leaned up so back in again to lower the float levels,,,,,,she responded

I played with some old mercury gauges at first,,,,,I have to remove the lower fairing to get the yics tool in so an also wanted to tune for the highway more than anything long story short I mounted 2 vacuum gauges on the fairing an started testing,,,,,I got the carbs balanced at speed fairly well an the bike got smooth out on the road,,,,,,an gave me something to shoot for,,,,,but it was terrible in the low speed stuff,,,,,,different approach I got up to 70mph closed the throttle an balanced for equal vacuum,,,,bike got smooth at the bottom an good under light load but a trend appeared #4 dropped vacuum fast under load an the vibs picked backup,,,,at this point I'm hooked I gatta chase this,,,,then I found #1 also dropped quicker,,,,,shims on top of the diaphragm springs helped a lot,,,,,bike is smooth,,,,,,#3 is the lazy dog an when I go back in I will be looking hard at it...

vibration is very dependent on the balance of vacuum I already new this but now I have an even greater understanding...
now I need to know what is the best way to tune this,,,, when you back off the gas an open it back up it just feels so much smoother when they are balanced this way,,,,,I'm in deep an will be looking at more things this winter,,,,,,bike has 67k an I need to keep this in perspective,,,,I love to tune an I'm bringing my knowledge up,,,,this bike is telling me it's got better days ahead,,
I was very careful with my testing now running #8's lean an able to pull 70-80mph for a few hours,,,,in my opinion she's rich at low load leans out as you ask for more than rich-ens backup as she gets on the main jet harder....she's very smooth cruises down the road with very little throttle an I might add that I was also looking for more speed with more vacuum pushing harder an harder for the sweet spot
an I'm not sure how long she will hold this high state of tune,,,,an I am now at a compromise with the balance at closed throttle an under load because I have no way of adjusting all this easily,,,,,,an this took a lot of testing,,,but the results are very rewarding for me,,,,,a motor in a high state of tune ready to be tweaked,,,,,for some it's the 1/4 mile they could care less about what I'm doing but I have seen that if you get it right she will howl better,,,,,
this is road my tuning went down where do I want to stop when is good enough I don't know ,,,,would I teach this approach,,,,I don't think it can be,,,I think it's been said by another xj member I do it for a change of pace when I want an walk away from it from time to time it is what it is,,,I don't have a clear path mapped out for how to get it any better I'm looking for it thou
well maybe she's a little more than almost dialed in,,,sorry you ask now aren't you

 

I think those Big Mikuni's your running on that 900 need a Diaphragm Piston Bore Cleaning and re-finishing.

My 900 was not giving me any engine braking and the revs were coming down too slowly below 4,000 rpm and Idle.

Once she got to Idle ... it was fine. Acceleration was always good. But, that slow to react -- coming down, bothered me.

After a visit with the Racing Boys and watching them refinish the Diaphragm Piston Bores ... I did mine the same way and got ALL the performance back.

You need to lightly sand of ScotchBrite the Aluma-oxidation off the Bore.
Then, polish the Bore to a mirror shine with a Dremel and #-5 and #-6 Jewelers Rouge.

When you get the Bores shined ... they don't allow the Piston to bind causing acceleration and deceleration issues.

 

yes I wish I would have done that now in hind site,,,,,this is very hard to explain other than I'm having fun with vacuum gauges an trying to learn all that they can tell you,,,,just another tool,,,,my bike runs good rick real good she's a keeper,,,give me a year or 2 we'll have her almost perfect,,,,,,,
being able to put your finger on it an have it respond the way it should with predicable results is the heart of it all,,,,thanks for your help your one of few I believe do this for the love of it,,,,I know I why I do it,,,I've got buddies that think I'm a little bent but they trust me in the turns an with there carbs we will have those bores mirror smooth soon
an I have got a lot farther in this because of this forum lots of great people here,,,,,

 

That was a mouthful.

You're sure right about all the good people.

 

update on the vacuum gauge tuning,,compromise is out I had sacrificed my idle trying to understand this,,,getting a finger on the vacuum at speed under load was my goal,,,this was never intended to replace the yics tool,,getting a sync at idle is easy,,,goal has been met.
the word perfect can not really be used yet
I have the vacuum pulling equal at closed throttle and at speed an all shims removed within reason it will take some more tweaking to get it perfect or find some other blip
,,,,,,, I can change the vacuum she pulls under load with the air screws,,,I can change the vacuum she pulls closed throttle with the sync screws. should be a matter of plug checks to move it richer or leaner,,,some day I'll take the lowers off an check it with the yics tool in...schools still out on this 1
so take it for what ever it's worth. that's the short an sweet of it,,,so far I have only searched for what the air screws affect....
bike runs good,,,better idle,,, it has better throttle response,,,it pulls better an easier,,, I have some vibs to try an work out in the upper 60's range um,,,um...I'm not done,,,
my tuning takes place in between other problems showing up.I would like to get to the wiring for the pickup coils as a new problem seems to be poping up,,,,something like mhhpartner problem with the pick coils,,,,seems like clockwork she goes off about 10mi out,,,I thought it was a float hanging but it's to consitant,,,,picks back up after a long minute,,,,,we'll get her sorted out....

 

Just try cleaning the Pickup Coils with Alcohol and Q-Tips. Sometimes there's just enough grime on them to make them not react the way they ought too when the motors running.

That, and trace the wire out from the bracket out around the case. There's a small protector plate forward of the case that the wire run under. If those wires are twisted or pinched in there ... the signal can get interrupted.

 

Here's a tweak I need to do, or find out how to do....
I get severe engine braking in 1st and 2nd, not bad in 3rd....4th is sweet...

What can I tweak to make the lower gear more friendly on decel...

 

You can do a Plug Read and see how you're burning right now.

If you find the Plugs are NOT a Medium to Deep Brown ... you can ADD some RICHNESS to the Mixture.

You have to do it a little bit at a time. Tweak INDIVIDUAL Cylinders as the Plugs dictate.

Bring OUT the Mixture about the width of a Nickel on those you find to be a little bit Lean.
Don't do anything if they are "The Good Color"

Don't Tweak what don't need Tweaking!

Darker Brown will give you LESS Engine Braking and Smoother application of Power.

The LIGHTER Colors will give you MORE Acceleration and Braking.

There's a fine line. The "Window" is about the width of Nickel (or just a Degree or two more,)

 

Thanks Rick....
Now I need a good day to do a highway run and test.....
We're looking at 3 days of rain.....work riding only..no fun stuff......

Thinking it may be a bit lean as I have tons of acceleration and lots of braking....
With my riding habits, smoothness and less braking would be great....

 

Don't Tweak them across the board.
Do INDIVIDUAL Cylinders ... now, as needed.

The process totally depends on the Plug Read.
The window is:

Light Brown (sometimes Yellow*) for Acceleration and Engine Braking
Med. Brown for Sport Riding ... Quick off-line -- Less Braking
Dk. Brown for Crusing Smoothness. Coasting instead of Harsh Braking.

You have to judge each hole on its own after closely examining the Plugs.
You may need to do them all.
You may need to do one or two.

Begin a record of what you are doing so you can always RETURN to a spot that has given you ... what you like ... as Ideal Performance.

The one Caution!
The Lean condition is addictive.
The bike runs like a F/1 Open-wheeled Race Car.
But, its too lean to be good for the engine. You risk damage running too Lean.
Major Problems can result.
Having a bike equipped with an Oil Cooler does help the situation ... but, will do NOTHING if the burn gets so hot it will damage a Piston.

If you do a Plug read and the Ceramic surrounding the Plugs center electrode is worn or shows hairline fractures ... THAT'S TOO LEAN!!!

Beginning to "Use Oil" is another dangerous sign.

DON'T let "Fast" infect you. The only thing that's fast ... is how quick you'll do some harm to the engine running critically Lean!

 

may it help to discuss the bypass hole, 4-2 of the 1983 yamaha xj900rk service manual has a pic showing a bypass hole, over the winter I noticed this an thought opening the air screw should give more air, but as soon as the butterfly opens past it,,,it's no longer a bypass hole but full on the primary circuit,,,sort of a power valve of sorts leaning the mix at closed throttle..
don't know how many have this, seems like a simple power valve setup to me. there is a need to lean the mix under engine braking or high vacuum,,,

 

The Carbs on the 900 are different from all the XJ-Family. The 900's Carbs are as Close to a Full Race Set-up as you could want to have on a bike. That, plus they are the Largest Mikuni's used on any of the XJ-Family.

My 900's are still Factory Fresh. I don't know how they tune them at the Factory prior to being installed ... but, the Pilot's are still Plugged and I'm not inclined to mess with them because Plug Reads have always been excellent.

Even after an afternoon of Harley Hunting ... the Plugs are within a range showing me that the Mixture is ideal and with that ... all I've had to do is a routine cleaning every now and again.

Even when she's sat for a bit ... weeks ... she fires-up and responds like a thoroughbred!

 

since getting the handle on this,,I've gone back to the rich side,,,,opened it up brought the strong ones back,,,,then micro tweeks,,,,I'm in shock as to how good this is,,,
the difference between lean an rich is there an I'm doing micro tweeks to get it,,,,I'm in heaven,,,

 

DBurnetteSr:

From what I can tell from the small picture - your 900 is GORGEOUS!

Regarding your new issue...

My little Seca originally just developed a consistent "flat spot" between 3000-5000 rpm at the end of my commute. Later, it would occasionally fall on its face while blasting down the interstate (just like it had run out of gas), but would pick up again after a minute and run fine.

In the last few days before I found the problem, approximately 15 minutes into my trip it would suddenly lose power, and would not go over 45mph until it sat and cooled off.

My service manual said the pickup coils should show resistance of 160 ohms (+-10%) at some certain temperature. My faulty pickups showed resistance (cold) of 60 ohms and 113 ohms. The replacements out of the donor bike both were in the 130-135 range.

This was lower than the specs and concerned me somewhat, but perhaps it was due to the hot temperatures we were having. (I'm not enough of an electrician to know how strongly temperature affects resistance.)

At any rate, my bike is singing a happy tune with the pickup coils from the cadaver bike, and I'm enjoying riding again.

Good luck-
Herb

 

thanks mhhpartner I'm getting an appreciation for how rare this fairing setup is,,,an would recommend people to howler if they find 1...
your description of the problem is very familiar when it happens I switch to prime because it feels just like running out of gas,,,but I don't think that's it,,,last time it did it,,it was worse an felt like 2 cylinders dropped out,,,I've got my winter projects lined up I think, I have to take the lowers off to get in there, not that hard I don't think just never done it,,, an it's a new problem,,,,,,I'll do the cleaning an check resistance when I'm in there,,,,new 1's are pricey I may look for a backup,,,or wonder if they can be rewound,,,I need to research this more for sure,,,I've got another project that got pushed back again when I got all excited about this tuning stuff,,,this bike is very addicting,,,again thanks

 

DB:

You "should" be able to check the resistance where the pickup wires plug into your TCI unit (under the left side cover on my bike).

I say "should" because I never was able to make adequate contact with my probes in the connector, but I didn't try very hard because I was swapping the pickup unit out regardless.

On my bike the pickup connector is the smaller of the two that plug into the TCI box. Your service manual should tell you what color wires to check for resistance.

Used pickup units for other XJs are commonly available on e-By for $25-$40, but I know the 900s are more rare. If you find out that you need one, you may want to try riderparts.com. I've had good luck finding obscure parts from their network of salvage yards.

Regards,
Herb

 

I'd look into the Diaphragm Pistons sticking -- and / or -- Fouling of the Emulsion Tubes not causing the stream of Main Jet Fuel to be fully atomized when the Throttles are opened.

The "Sticking" problem is prevalent with these Brass Piston Diaphragm Pistons.

The Brass tarnishes and the Aluminum Bore oxidizes causing the Travel of the Piston Up and Down to drag, stop or hesitate.

Eliminate the possibility by re-finishing and polishing the Diaphragm Piston Bores. The Bike will run like new again!

 

I've put the bike in the garage an refuse to get a wrench on it till I get some other stuff done,,,,,,we'll shine the bores soon rick,,,Brass Piston Diaphragm Pistons,,, I don't rememder them being brass I'll pay more attention next time in,,,,,
Emulsion Tubes I'm big on also every hole,,,I've got those super tiny drill bits that go in the .001's an checked every hole the plugs we're black I was looking for all the air I could get,,,next time the bores get shined,,I'm sure I did not leave the bores real bad as I'm aware of the piston's need to move,, just did not get the buffer out..
I'm able to go lean so I should be a shine an a few tweeks from any where I want to be,,,,the only spot I see open to more tweeks are the main jets,,,the low end if you can call it that goes till about 75-80 can be dialed in anywhere rich or lean,,,,, need more long runs an the weather is not looking real good but I did see some sun trying....I just hope it's not rich,,,,I pulled the plugs I'm still showing lean but that was a short highway jump,,,,need to do some city driving see if it soots up a little,,,I really like this feeling,,,,sort of reminds me of eletric motor type power with a very good controler,,,only decription that jumps to my mind not a ring dingy power,,,

 

You'll feel the difference and hear it too!
Lean has a "Growl" to it and the Throttle Power is very responsive.

Rich has a muffled sound and can be so smooth its almost velvety feeling.

You definitely know in the engine braking arena.
Lean will slow the bike right down when you close them Butterflys
Rich has a sustaining "Coast" happening along with it.

 

OK, got some tweaking in yesterday, was running lean, so I tried a half turn on each carb, barely a difference, so I went a full turn, now a nicer growl, less engine braking and smoother response from the throttle.....

Also tweaked the clutch cable a bit, less of a clunk going into 1st...

On the downside, starting cold this morning took a bit more effort.....
and I seem to have a dead spot if I set the choke about halfway...
More cleaning? Any good tweaks for the enrichment side of things?

 

The Enrichment Circuit is wholly dependent on the Fuel allowed to be drawn topside by the four small brass Siphon Tubes and the supply of fuel to the wells they are extended into when the bowl is fitted to the Carb.

If the Bowl Bottom jets allowing the well to fill are clogged the entire start circuit is rendered inoperable or has poor performance.

The Siphon Tube has some of the smallest openings there are. You might need to flush them out; too.

 

That's what I was afraid of..... I thought I had them clear, guess not fully....
Works fine on full, but there's a rough spot when it seems to try and kill as I start to close, either side of that point is fine.....revs will drop below no enrichment at all at that mid point....

I cleared the bowl bottom jets when I fixed the jetting issue, BUT I didn't check the brass tubes.... that could be the ticket.....

You would think the issue would be more pronounced with a lean mixture though....after riching it up, I should need less enrichment to go.....

Will fight with it this week, damn, is that more carb cleaner I smell

 

Get a Rubber Syringe and do a flush. Best tool for doing Air & Fuel Passages I know of.

 

I need to grab one of those for the kit...thinking plastic ones will get eaten by the cleaner hehe

Otherwise, it seemed better today..... gotta add a brake line bleed and flush to the todo list, as well.