Lean when cruising.... AGAIN!

Instead of reviving an older thread, I'm starting this one and condensing all of the information.

When I am cruising, I did several plug chops between 5,000 - 6,000 RPM and plugs 3 and 4 were WHITE. At idle, they are nice and tan or even darker.

Now, this is what has been done to my bike:
-ALL jets (including air) are correct sizes
-New airbox to carb intake boots
-New gaskets for intake manifold at head (intake boots are fine)
-New ignition pick-up coils and plug caps.
-Carbs have been meticulously cleaned, and once again yesterday. EVERY passage is clean, I blew air through each hole on the carb and felt it come out of it's respective opening.
-New air filter
-New plugs

Now, carbs 1 and 2 are running fine and set at 2 turns out. Carbs 3 and 4 are set at almost 5 turns out. When running them at idle, the plugs turn a slightly darker color than those of 1 and 2, but when chopping the plugs for 3 and 4 are considerably lighter. If I turn the pilot screws back down to 2.5 turns on carbs 3 and 4 and plug chop at 5k RPM, the plugs are WHITE.

My gas mileage is right around 33 MPG (terrible) and I can smell gas fumes from the exhaust when I am parked at a light.

I have fixed all of the electrical issues and the carbs are as clean as can be. My only other concern is that I am leaking air into the system somewhere but I am unable to find where.

What could this be? Carbs 1 and 2 are operating perfectly, while carbs 3 and 4 are off... is there something that would link carbs 3 and 4 and cause an air leak?

 

Thats an awfull lot of turns between the carbs pilot screws mine are all with in about a qaurter to half turn from one another,Did you make sure all of your pilot screws had good o rings and that the little washers were there and not mistakenly doubled up?And or you made sure all of your seals on your throttle linkage shafts were not leaking,I had one that was bad and it took me a day to find it,and then I had to re sinc and swear alot because I missed it.

 

The carbs have been rebuilt with new throttle shaft seals, the pilot mixture screws all have new washers and o-rings. Throttle shaft seals had some silicone grease applied to them, too.

I should also add that with the clutch pulled in, under hard braking using the front brakes the revs will drop well below idle and sometimes it will die altogether.

 

I don't think your Diaphragms Pistons are all rising and falling without interference.

I'd SCRUB the Diaphragm Piston Bores with ScotchBrite Pad (Medium/Gray) and follow the Scrubbing-out with a Polishing of the Bores.

Scrubbing Bores:

Polished Bore Surfaces:


CLICK on LINK in my Signature >> "Clunk Test"

 

Rick,
what do I use to polish the slides themselves? I have used the green scotch pad and 800 emery cloth, but I still get a bit of stick on 2 of 4.
in fact, I just pulled my plugs and #2 was lean. 1, 3, 4 look good.

I bench-synced a few weeks ago when I was having a lot of starting problems, and I used a piece of wire as a feeler gauge. I got them perfect on the bench and the bike is running great now. just doesnt return to idle very quickly.

 

Ricks the man !!

 

You don't need to Polish the Slide.
You just have to make sure there isn't a build-up of any kind from sitting-around.
I have yet been able to remove the "Smile" on a Slide Piston.

I have tried:
Never-Dull
Brasso
Noxon
You name it, ...

Just be sure the Slide Piston moves Up and Down through the Limit of its travel without Binding.
Swap them all around if you have too.

You just have to be absolutely SURE ... They are going to Rise when they should and get pushed-closed by the Spring when there's less flow.

But, ... A nice set of Polished Bores is going to allow those babies to Rise and let the Motion Lotion Happen like Hell when you wrist-it open and want the thing to MOVE OUT!

 

what is a plug chop ??????????????????

 

search

plug chop

 

Rick - my slide's clunked, but I went through and read your article about the "clunk test" and took today to get it almost "Race Prepped" as you put it. I used the scrotchbrite pad to scrub the bores, then used 800, 1000 and 1500 grit sandpaper with the WD40 to polish them up. WOW! It made a HUGE difference in the way the bike runs... however, I am still lean on 3 and 4.

I took the bike out on the highway for about 5 miles, chopped the plugs and both 3 and 4 were equally white. I turned the mixture screws back out to 5 turns and limped it home, keeping the revs as low as possible

I also ran a little test and swapped plugs 2 and 4 and chopped again on my way home to find that the plug I put into cylinder 2 (originally from 4) had acquired only a tiny bit of color, but was still mainly white. The plug in cylinder 4 (originally from 2) had kept the same brown/black color.

What is happening here? This bike is my only mode of transport and it's really disheartening and disappointing that after all this work and money spent it still has kinks to be worked out.

 

I should also add that I swapped the diaphragm from number 3 to number 1 to see if there were any microscopic holes that would cause this issue, but the number 1 plug is still good.

 

mestnii-
it sounds like you are getting extra air in somewhere...
when you synched, did you block off the YICS? it sounds like the air you are getting isnt coming in at idle, but requires a little more vacuum to come in. have checked the vac port plugs on each intake boot?
did it just start happening or had you worked on it when it started?

 

Are all of your plugs the same heat range?

 

iwingameover - all of my plugs are NGK BP8ES, the ones specified for the bike.

helmet - I synched with the YICS blocked off and also open, I noticed no difference. The vacuum plugs are new and I even tried swapping the ones from the "good" cylinders to the "bad" ones with no change. I fixed everything on the bike and then started plug chopping, that's when I noticed the issue.

I have to add that when I pull the clutch in, my revs drop right away. I know that on cars a vacuum leak causing a lean condition will cause the revs to spike. Does this hold true for bikes? Also, after I polished the diaphragm bores, the engine no longer bogs under heavy braking... so at least that problem is solved.

What I don't understand is why my gas mileage is so low if I am running so lean. It's even weirder because a few weeks ago I was doing a lot of 2up riding and averaged 37 mpg and now riding alone I get 33. Keep in mind this is driving conservatively.
It's also weird to me that when I switched the plugs for my ride home, number 2 did not get any more color on it even when the revs were around 3k during the entire ride.

 

have you checked compression?
also, as a last ditch effort, what about breaking the rack and moving carbs around?
I probably wouldnt do it, but with everything you have done, it seems really strange that the problem exists like it does.

 

helmet - compression tested fine on all 4 cylinders, within 4 PSI of each other. As far as breaking the rack and switching them around, wouldn't I only be able to move number 3 where number 2 is? 1 and 4 would have to stay in the same position due to the location of the fuel rail passages.

I am equally as perplexed as you.

 

You are either getting ADDITIONAL Air introduced making the Mixture too Lean, ...
-Or-
Less FUEL is getting delivered.

I'd look for an Air Leak, first.
Loose Carb Neck Clamps
Carb Neck Clamps too tight / Manifold cut through at clamp
Manifolds cracked; leaking upon High Manifold Vacuum
Cracks at where Manifold Rubber meets Manifold Attachment

Intake Manifolds Rubber O-ring Seals breaking-down; leaking under Heavy Manifold Vacuum
(Don't risk removing Manifold if Fastener is Seized -- Seal Perimeter)

Carb Throttle Shaft Seals.

Pilot FUEL Jets partially / clogged
Pilot FUEL~AIR Passage clogged
Pilot AIR Jet + Main AIR Jet reversed

Wrong Pilot FUEL Jets
Sync Tube Dunce-Caps loose

TEST:
Silicone Caulk around Mating Surfaces of the two Lean Manifolds.

 

Rick - I've checked all of my jets against the sizes in the manual, they are all correct and in the correct place. All carbs have been cleaned in the exact same way, ensuring clean passages.

I will caulk around the mating surfaces of the lean manifolds and take it out for a spin and let you know what is happening.

 

Rick - I put a small bead of silicone caulk around the manifold where it meets the head. Took it for a short drive right away and there is a pinhole where some air has been sucked through. This is startling news to me as I have replaced the manifold gaskets just two weeks ago.

My intake manifold bolts came right out, so I plan to take them off again and use gasket maker for a better seal. Is PERMATEX® ULTRA COPPER® Hi-Temp RTV Silicone Gasket Maker safe to use? (http://www.caswellplating.com/permatex/ ... akers.html)

 

For the Manifold Gaskets in the Case of the Fasteners not being seized, ...
this is what I'd do.

Remove the O-rings from the locating channel on the backside of the Intake Manifold.
Replace them with the appropriate Metric-sized O-ring, ...
(Does NOT Need to be a Yamaha Part.

Make 8 Gaskets
Get Dowels that fit Head Threaded Holes
Get "Indian Head Gasket Shellac"
Cut-off the Applicator Brush on the Cap.
Get some "Cheapo" disposable "Real-small" Brushes >> 3 or 4

Using Brush-on method:
Place Tin Foil to catch drips.
Coat Head
Insert locating Dowels
Coat Gasket
Place first Gasket over Dowels and seat it to Head
Coat Gasket just seated to head
Place second Gasket on Dowels
Seat second Gasket into Sealant
Coat second Gasket
Coat Manifold backside
Pull lower Dowel
Coat BRAND NEW Hardened or Stainless Fastener with AntiSeize
Place Manifold over Upper Dowel
Start Lower Fastener to Finger Tight
Coat second NEW Fastener with Antiseize
Pull top Dowel and Start Fastener
Tighten Finger Tight.
Smoosh**
Tighten to Specs.

 

Is it really necessary to use two gaskets AND the O-ring Rick? Just asking cause my intakes have the O-rings and RVT and that's it.

 

I suppose the RTV alone would seal it.
I went for Over-Kill because I didn't have new O-rings.

I sealed it up tight and could see the results during a hookup to Carb Sticks.

I just didn't want to have to pull the Carbs, again, on a job that I already had a good deal of time into and was getting tired of chasing the Manifold leaks.
I gooped-'em-up tight and made sure that they weren't going to leak ever again.

This came at the end of a trying time trying to isolate the "Hidden Leak"

 

Ahhh ok i got ya Good tip if you don't want to have to worry about it.

 

Rick - I sealed up all 4 carbs with RTV and it helped big time on cylinder 4's lean issue. I took it for a few short rides and the plug is a nice brown color now.

Cylinder 3 is another story, as it is still WHITE. Where else could an air leak be coming from?

I will take a highway ride and pull the plugs to let you know if the issue with cylinder 4 is completely resolved.

 

Also, I used a part's list from Chacal to verify that the XJ700N only uses a GASKET, no O-ring, when mounting the intake manifolds to the head.

 

Have you considered the possibility of some sort of air leak through the petcock or a cracked vacuum line? It might be worth a shot to swap the cap and line of #2 cylinder and #3.

Maybe it is possible that petcocks can fail in such a way that they leak air and not fuel.

 

fore4runner - I have vacuum caps on all 4 intake manifolds and a new on-off fuel valve

So... I took the bike out for a ride on the highway and plug chopped at 5.5k and both 3 and 4 are showing completely white insulators.

At idle with 2.5 turns out, number 4 now turns a nice brownish color, but 3 is still white until I get it to 5 turns out.

What other ideas does anyone have?

 

I know this is going to sound kinda strange and Rick you may have some insight to this as well.But speaking from experience I've had the same symptoms once before and what was happening to me was Not knowing I had a weak charging system that worked when it felt like it and my battery wasnt the best because of it.But the battery being fairly new I never gave it a second thought that it might be electrical but after biting my tounge and delivering my machine to a dealer they discovered the problem after a week or so.The tech explained all about having the correct voltage to energize the charging system,and then the charging system quitting on my speraticly without my knowledge the bike would be running on the battery alone and the weaker it got the weaker the ignition voltage from the coils is/was.Your charging system could be like my bad one and start to fail when it gets warmed up and causing you some trouble or not, But it might be worth a look both cold and hot to see if it might be suspect.

 

You need the Battery and Charging System to be right or you'll be pushing the Bike home.

Inspect the Alternator Brushes for being in Specs. = 10mm. Min.

Connect a Volt Meter to the Battery and check Specs.

+12V at rest ... 11.4 Cranking ... Increasing upon Start back to +12V
increasing as RPM's increase ... to: + 14.2 V -at- 1,875 RPM's >> +14.5 V -at- 2,000 RPM's ... sustaining +14.5 V as RPM's increase beyond 2K. 14.5 V Being optimum -- Never exceeding 14.8 Limit.

In numerous cases before present day, I have found the Spark Plug Wires to be at fault for a week Spark.
The Plug Caps are twisted into the end of the Plug Wire where sharp, self-tapping screw points engage the Copper Strands of the Spark Plugs Wires Center Core.

Over time, the Plug Cap loosened, ... Pulled-off, ... and was re-inserted into the Spark Plug Wire >>> where the Center Core Strands became damaged by the Screw threads in the Plug Cap.

Eventually, the Center Core Wires disintegrated to such extent that performance was compromised.
"Cutting-Back" the Plug Wire End rectified the fault until the Spark Plug Wires became too short to "Nibble".

This, combined with + 20 years of time for the Plug Wire to "Break-Down" and allow the Coil to discharge to Ground along the length of the Plug Wires (in advanced state of deterioration) is a common cause for the Engine to misfire.

The solution is NOT as simple as it is for servicing an Automobile where the Ignition Parts were designed for relative ease in exchanging.
We cannot install a New Distributor Cap and Wires.

We either have to become Surgeons and exchange the Spark Plug Wires protruding from being solidly mounted within our Coils, ... or,
buy new Coils and Wires that require a measure of fabrication to get them mounted where they need to be.

Oh, yea ... the Coil People see us coming; so their Motorcycle Coils don't come cheap.

(in many cases I have stripped some Ignition Wire ... twisted the Copper Strands as tight as possible ... and --> "Stuffed" what I twisted-up as far up into a Plug Wire as it would go before trimming-off the end and doing that Mod to extend the life of a Plug Wire.)

Test:
Use Caution -- Don't run the Bike for long within a confined space.
Start the Bike and L@@K at the Spark Plug Wires in pitch dark.
If there's nothing to see ... you're OK
If it looks like a Lightning Show ... you got troubles brewing.

 

The battery is new as of this year and I ran the whole gamut of electrical tests on it. It is right around 11.4 at cranking, 12.3 - 12.5 at rest, rises to 14.2 at around 1800-1900 RPM and maintains 14.3 - 14.5 above 2000 rpm. I referenced these numbers and it seems that 14.2 is the minimum voltage for a battery at above 2000 RPM.

As for the plug wires, wouldn't a weak spark cause a RICH condition?

None the less, I will pull my alternator out and double check the brushes as well as try inserting some twisted ignition wires into the plug wires tomorrow.

I am getting desperate to fix this bike in time for my move and will try just about anything to get it running right.

 

this thread has me thinking i should hook up my volt meter and go for a ride.

 

after you patched the holes, did you check the sync again? having a small air leak would give a false sync reading. since everything is set to 3, it would seem par for the course that the others are off from 3

 

Ok, so I went through my bike again.

I check the brushes, the were well within spec. Resealed the intake manifolds, covered the actual boots with liquid rubber in case there was an air leak and synced the bike.

Took it out for a highway ride, pulled the plugs and both 3 and 4 re still lean while 1 and 2 are now covered in black soot.

What bothered me was that plug 4 had a small, silver/gray patch on it, while plug 3's insulator was almost entirely covered in a light, shiny film of silver/gray. It is most like the "too hot" picture here http://www.aa1car.com/library/reading_spark_plugs.jpg

I also took the carb hats off the bike as soon as I parked it and pulled the diaphragm and needle assembly. Carb 1s bore had a thin coating of gasoline on it while carbs 4s bore was completely dry. Now I'm thinking I'm not getting enough gas? If that's the case, why am I having such poor gas mileage?

Ideas?

 

One problem easily overlooked is a Pinhole Leak in the Petcock DiaPhragm.

The Leak allows Fuel to be drawn-up the vacuum Hose by still works the Petcock.

Make a Vacuum Bottle that will Separate Fluid from Air and try applying some vacuum to the Pilot Mixture Hole without the Screw and washers in there.
See if you are drawing Fuel through the Pilot Passages.

 

Rick - I have an on-off fuel valve on the bike, does this test still apply?

If so, let me know if I understand this correctly. The bottle has 2 hoses, one goes snugly into the open pilot screw hole, the other to the vacuum port. I then turn the engine on and leave it running watching for fuel to be drawn in to the bottle?

 

No.
Not Running.
A Pilot AIR~FUEL Passage Test.
Removal of the Pilot Screw, Spring, Washer and O-ring ... necessary.

Vacuum Bottle Test:
The Bottle has two Hoses.
One > In through the TOP and all the way down to the Bottom of the Jar.
Two > In through the Top and only 1-1/2 Inch long.

The "Long One" gets used to apply Vacuum to a Port where Fluid will be extracted.

The "Short One" gets hooked-up to the Vacuum Cleaner Hose and Sealed-off with Duct Tape.

When the Vacuum Cleaner is turned-on:
Vacuum is applied to the Short Hose, ...
(which)
Creates a Vacuum in the Bottle
(which)
Applies Vacuum to the Long Hose
(which)
Draws a Vacuum on the Port being Tested, ...
If Fluid is present in the Vacuum Tube ... It exits the Long Hose and collects in the Jar, ... rather than being drawn into the Vacuum Cleaner.

WARNING <> WARNING
At once you determine that the Pilot Fuel Passage is NOT clogged because Fuel gets drawn-up by the Vacuum >>
SHUT OFF THE VACUUM
Empty and Clean the Jar
Purge the Vacuum with Fresh Air

Too much test make vacuum cleaner go Boom!
Use ugly Vacuum Cleaner
Not wife's new Dyson!!!

"What was that noise?"
"Sorry, honey!"

 

Thanks for the explanation Rick!
I'm still working on getting a vacuum cleaner, not something a recent college grad has in the home.

I've been doing some more testing with it and messing around. I put a .03" washer under needles in 3 and 4, sync and went for a run. Fouled the plugs COMPLETELY within the first 3 miles.

Got home, took out the shims, sync and then colortuned. Now I was able to adjust the mixture from orange to blue on all carbs EXCEPT number 1. Went for a ride, 3 and 4 are now a tan-ish gray color, 2 is black and 1 is completely white...

Hmmmm... now what?

Is it possible timing is off? Is it possible the needles NEED a small shim .01" maybe?

 

Clean the YICS Passage.
You need an Old Athletic Sock or some Terry-Cloth
A Ram-Rod (Fiberglass Driveway Marker or Wooden Dowel)
A Hammer (Combo Plastic/Rubber Ideal - Rubber Mallet OK - Regular Hammer OK)
<> Phase One <>
Remove BOTH YICS Chamber Ports
Cut a "Patch" of Cloth
Saturate with Carb Cleaner
Insert into YICS Chamber
Use Ram-Rod to drive Patch through Chamber and out opposite end.
Keep sending CLEAN Patches through until the Patch you load exits as Clean as it was when inserted.
<> End of Phase One <>

<> Phase Two <>
Replace Right Side Plug
Cover Left Side of Passage with Thumb
Run Bike
Moderate Vacuum should be present upon Thumb
Slip Carb Cleaner Red Tube under Thumb >> Preventing Tube from being sucked into Chamber >>
Push Thumb re-establishing vacuum
Release Carb Cleaner into YICS Chamber in >> short burst.
<> End Phase Two <>

Replace and Secure Both End Caps.

No. The timing can't be off.

Investigate No.-1 Manifold for Air Leak
It's getting too much AIR or Not enough FUEL.

(I'm betting AIR at the mating surface of the Intake Manifold to the Head)

 

if you hook the sync sticks to one and 2, what do they show now?
is the bike fully warmed up when you sync?

 

Rick - I was doing a partial tear down and a voice inside my head told me to take a look at the carb 1 diaphragm. I opened the up the hats and found the diaphragm/needle valve stuck closed due to some particle. Cleaned it up, put it back on, and now the number 1 cylinder is DEAD ON PERFECT!

Cleaned the YICS passage and checked the carb bores/diaphragms on the other 3 carbs. Cruised around for a bit, plug chopped at 5.5k RPM and have the following results:
1 - Perfect
2 - slightly rich
3 & 4 - slightly lean (deep gray color)

I read another post that midrange leanness/richness is caused by the needles, not jets, so I swapped in a .02" shim for both 3 and 4 and will see how they perform.

In the mean time, how do I cure number 2 being rich? Also, what other ideas do you have about carbs 3 and 4?

helmet - the bike is fully warm when I sync. I did another sync and colortune after I found the number 1 diaphragm stuck and I was able to get all 4 carbs extremely lean/rich and then adjust for a nice blue flame. Using the 2 bottle set-up, the difference between carb 1 and 2 was very minimal in terms of vacuum pressure. It required about a 1/4 turn of the sync screw.

 

The ColorTune puts you in the BallPark.
Plug Chops and Tweaking the Mixture pits you right on Home Plate.

For the ones that are a bit lean ... add a couple of degrees of Richness.
If you have a Rich one, ... Lean it out a smidge.

Sounds like your closing-in on it anyway.
You might have to get rid of the shims when you get to making Final Tweaks.

 

mestnii-

glad to see you are getting it nailed down.

I have a week on the new plugs and oil, so I am going to check my idle settings and do some plug chops tomorrow before I pull it apart to prep for paint.
all my tuning was done on old plugs.... they were worn to say the least.

 

Once you actually get the Bike, ... "Right in the groove" ... where it is performing at it's maximum capability ... getting away from a Red Light with no delay, smooth idling and rapid throttle response in the Power Band, ... you get to the point where there's nothing more you can do.

You dialed it in.

It's a good feeling to be able to turn-on the Key and have your Bike start-up instantly and get you from point A to point B with a big grin on your face.

 

Rick - I colortuned to get in the ballpark and am now making the tweaks to get me to home plate. Cruised around and plug chopped. 3 and 4, with the shim in place, are now perfect, as is 1. 2 is still running rich and I will keep tweaking it.

Thank you all for the wonderful help!