1&1/2 turns out & still fouling

Float heights and fuel level perfect. all passages squeaky clean. perfectly bench synched with a guaged steel wire. All valves in spec and sealing well.

started at 2.5 turns out... started great then fouled plugs with soot
2.0 turns out... started great then fouled plugs with soot
1.5 turns out... started great, seemed to run a little better but then fouled plugs with soot again...

All 4 plugs look identical... black, dry, sooty

Sitting at idle for any amount of time seems to be when the fouling takes place.

Do I just keep turning or what?

I have a 195 pilot air jet installed instead of the 205... is that why I need to turn the pilot mixture screws in so much further?

Any help... as always... would be very much appreciated.

 

Are your enrichment circuit plungers closing all the way?

 

+1 on the enrichment plungers. Check and make sure the end of the choke cable sheathing is fully seated in its little socket at the lever end. When I use my "choke" lever and close it too fast, it pushes the end of the cable sheathing out of the socket it normally rests in. This lengthens the sheathing which shortens the cable and pulls up on the plunger levers letting enrichment fuel in and sooting the plugs. I double check and make sure the plunger levers are loose each time I use the choke.

 

TURN your screws out you are too rich you need to lean the fuel/air mixture. Start at 2 and 1/2 if black and sotty turn OUT and not in. You are making the bike run too rich.

 

Yes, I think this is how they work. turning counter clockwise (CCW) lessens the amount of vacume causing more air to flow and less fuel. Because, the fuel is Being Sucked out of the bowls, by vacume. So the larger the opening, the lower the vacume pressure. So CCW is more air and less fuel. Arguments are welcome, I'm not a genius

 

the following are for US models for an xj650 from haynes manual
Main jet - 110
jet needle y-11
pilot jet-40
starter jet-40
main air jet -50
pilot air jet -195
pilot air jet - xj650j, xj650-11n (UK) - 205

if enrichment plungers are seated all the way your sure air passages are clear.

if you cleaned the float bowl jets, did you accidentally enlarge the hole by using two big of a wire or drill bit.

fuel mixture screws enrich fuel. To lean the idle mixture turn them in clockwise. Using a color-tune plug you will see the change in mixture. turning screws counter-clockwise will cause a yellow flame which is rich, turing screws in causes bluish white flame causing optimum mixture, to lean will turn flame white.

Have you checked to make sure the air filter is clean and allowing enough air flow? Have you checked the airbox to make sure something isnt blocking air flow?

I'm in your area if you need help. just pm me.

 

spec calls for 3 turns out. roughly.

1 - 1/2 is too rich.

 

If you have a SMALLER AIR Jet than prescribed ...
You BEGIN with LESS Air

If you allow LESS AIR to be drawn in with the Pilot Mixture ...
The Air~Fuel Ratio is going to be INITIALLY Rich.
Less AIR ... More FUEL

If the process is too RICH at 1.5 Turns OUT ...
You need to:
INCREASE Pilot - AIR
REDUCE Pilot Fuel

You can't expect the WRONG Jets to ever produce the CORRECT Mixture.

With the "Choked" Air Jet ... (Smaller AIR Jet)
When you bring-out the Screw from the Bottom-out ...
LESS Air CAN be drawn-in.
MORE Fuel will be pulled-up to satisfy the Vacuum.
The more you Turn-out the Pilot Screw ... the RICHER the Mixture will be.

To LEAN the Pilot Mixture you need:
A Larger AIR Jet.
Stock or Smaller FUEL Jet.

 

Enrichment plungers are bottomed out with slack between the forks and the plungers.

I am going ahead on the premise that you turn the screws IN to LEAN out the mixture.

If all else fails I will pull of the carbs (yet once again) and replace the 195's with 205's and start over. Since the bike was always kept stock I thought maybe the Seca's had a different set-up from the factory for some reason. Oh well.

Thanks for all the help.

 

yeah I'm stupid, I know its In for lean for sure from using the Colortune. Ride On

 

No fellows, ... That ain't the way they work.

You turn the Mixture Screw OUT to ENRICH the MIXTURE.

The Pilot Mixture Screw is a VALVE that REGULATES the amount of FLOW into the Combustion Chamber.
The FLOW is: AIR ... Accompanied by Fuel.
Closing the Valve ... reduces the FLOW.
Opening the Valve INCREASES the FLOW.

The AIR --> BRINGS --> FUEL
The AIR Jet Regulates how much AIR gets to FLOW.

As you turn the Mixture Screw OUT from the Bottom ...
AIR is introduced to the Intake Vacuum
The MORE you OPEN the Screw ... The AIR begins to SIPHON Gas from the Pilot FUEL Jet Supply.

The MORE the Valve is Opened ... The AIR allowed to satisfy the Vacuum is REGULATED by the Pilot AIR Jet and the Vacuum is satisfied by MORE Fuel being Siphoned by the the Air Flow.

A New Member confused by someone's misinformation of this Operating Principle could easily make an ill-advised Mixture Adjustment that might very well cost him his engine.

That is NOT our Mission.

 

For the XJ650RJ Seca, the #195 pilot air jet is the correct size.

Also, these model carbs may have used the "coarse" thread pitch on the pilot mixture screws; if so, then about 1-3/4 up to 2 full turns off of the fully bottomed position is the proper "starting point" setting. Other carbs, which use a very fine pitch pilot mixture screws, use the 2.5/2.75 turns "out" from fully bottomed "starting point" setting.


Enrichment plungers: make sure they are fully seated, and, inspect the rounded/tapered area where they "seat" against matching tapered seat area in the carb body. We, too, have experienced carbs that always keep fouling plugs, and have discovered that scarring on the brass plunger "seat" and/or the seat area in the carb bore (which can be polished out by various means) solved the problem.

By the way, we discovered this because one carb in the rack wasn't fouling the plugs, and after we had exhausted every other avenue of approach/adjustment/possibility, that's when we stumbled across the scarred (grooved, scratched) enrichment plungers, and polishing them and their bore seats eliminated the fouling problem.

It doesn't take much of a flaw in the plunger or the seat area to allow the enrichment system to be passing some fuel, even if the choke plunger is "fully closed".....as the flaw in the plunger seat area, in effect, keeps the enrichment (choke) system "on" all the time!


Air jets: by the way, going up to a #205 pilot air jet was a change that was done when the 650cc engines got the YICS system; it's a change that has only a small effect on the overall lean or richness of the air/fuel mixture, and should be considered as a "fine-tuning" effect rather than a change that will grossly vary the overall mixture (such as a change in the size of the pilot fuel jet will).

The effect of air jet size on mixture is less dramatic than the effect of the fuel jets, which makes perfect sense when you think about it in this manner: a jet (be it an air jet or a fuel jet) meters the flow of a fluid through it by volume (and not by the weight of the fluid).

But air/fuel ratios of, let's say, 14.7:1 are actually expressed as the ratio of the two fluids by weight-----and since we are consuming approximately 860 times more air than fuel by volume (the exact conversion varies by the molecular weight of the specific gasoline blend being used in the engine, and the molecular weight of the actual air being drawn into the engine, i.e at higher altitudes a given quantity/volume of air weighs less), to have the same effect on performance as changing one fuel jet size, the increment of the area between air jets would have to be about 860 times the increment between fuel jets.

To put it another way: theoretically, the fuel jet diameters would have to be sized in increments of 0.00365mm to have the same effect on overall mixture ratio as a 1mm change in air jet diameter.

This is why air jet size changes are for ultra-fine-tuning purposes.......

 

you really shouldnt be fouling plugs with air idle ajustment screws. will change a bit by ajusting them but you would have to do a lot of time at idle or below 2k or so. is it blowing black smoke when you rev it? just for the heck of it check your float levels again. i have done some hitachi carbs before where the needle moves a little on the tang and changes levels. are you sure you have a good hot spark weak ignition will soot foul plugs in a heartbeat. your air screws are not bent or anything from bottoming out in the seats are the orings good under the washer on them ive seen them squished etc i never really seen to much difference after replacing but they are there for a reason. if you do have to pull the float bowls again look at your floats really close make sure they arent distorted or 1 float is higher then the other. also make sure where the pin goes thru the float isnt sloppy that will change your level after setting. just little things that can drive you nuts.
also check your battery if it isnt putting enough charge at idle it will start to discharge and your spark will get weaker and weaker especially if your battery isnt in perfect order

 

My experience with this sad story of Plug Fouling after a Carb Cleaning usually boils down to a few things:

1) Incorrect Jetting: The Carbs are perfectly Cleaned. Perfectly! But, some mistake was made with the placement of the Jets.

You need to look and see that you have not mixed-up the placement of any of the Jets.
BOTH >> FUEL and AIR *
* (The AIR Jet mix-up being a common mistake due to a misprint in the Data Section of Haynes.)

Proper AIR Jet Placement:


2) Improperly re-assembled Enrichment Plunger Assy's
and Damaged Enrichment Plungers.

The Mechanical Hook-up on the Enrichment Valves is too tight and the Valves are lifted off from their seats. Pushing down on the Valves to check is negated by the tight Cable.

The "TOP-Hats" on the Enrichment Plungers are BENT.
The angry use of the Choke Lever on a Bike that doesn't start causes the Fragile Top Hat of the Enrichment Plungers to become Bent. The Bent Top Hat cannot allow the Plunger to seat.
( If the Top Hats are Bent, ... remove them to straighten them.
They are easily Broken off. Heat the end and gently reposition it with narrow Needle Nosed Pliers of Roll it on a sheet of Glass while still hot. Wear gloves.)

3) Pilot Mixture Screw Parts -- "Flip-flopped"

While replacing the Pilot Mixture Screw Parts ... all the Parts are assembles on the Screw an placed in the hole. The O-Ring and Flat Washer fall-off and tumble-down to the bottom. As they do, the O-ring loses the race. The Parts are REVERSED and the O-ring is in the wrong place, ... so the Pilot Mixture Screw does not fine-tune. As it is brought out its effective wide open.

 

OK... Update...

I did a "plug chop" finally (benefits of getting the bike out of the city)

Insulators were BRIGHT white and outer electrode on the plug was blistered and yellow.... Way way way too lean

Turned the mixture screws out a turn and a half and did another plug chop and the insulators are now ivory colored so we are getting closer to a good mixture.

The bike still fouls plugs at idle. only takes 30 seconds to start cutting out and missing

The bike blows black smoke when you rev the throttle

I replaced the battery

I checked the spark plug end of the coils and they check out

Other than checking the other side of the coils and maybe replacing the spark plug boots with new ones (closer to 5K ohms) what am I missing?

 

Float levels. That's what you're missing-- float levels. Get one too high and it will foul plugs no matter how much you tweak the screws.

Dry setting doesn't cut it. Use the clear tube method with gas.

 

also make sure your seats arent leaking by you say takes about 30 sec or so to start fouling take a pair of vice scrips pinch off the fuel line start it up let it run for 20 sec or so let it idle release the vice scrips for a few sec and reclamp see if it takes longer to foul. if it fouling that quick it has to be level or bad needles and seats

 

I would double check to see if the AIR Jets are where they really belong.

 

Compression check? Stock Exhaust? Air filter type?

 

I'm going a different route for a possibility seeing everybody just about covered everything else. Did you check the primary side resistance of the coils. If I'm reading your post right you only checked the secondary resistance or the spark plug side.

The reason I say this is I had massive plug fouling on 1&4, bike ran fine at high speed but at idle slight skipping and it stunk. The primary resistance on the coil read around 3.5 or 3.6 instead of 2.5 ohms. Secondary side checked out fine.

I replaced both coils with dyna coils and when removing old coils there were severe cracks in the case of 1&4 on the underside also which I wouldn't have seen if I hadn't removed them.

I'm not saying this is your problem but it is easily checked with an ohm meter and if the readings are fine, its one less thing on the potential list of culprits.

 

Float levels are all within spec... I checked them wet not dry. All of the jets are properly located. All of the needle seats are properly working as you can leave the petcock on prime and not flood the carbs.

primary side resistance is at 2.7 for both sides... seems to be within the 10% plus or minus for "within spec" Spark plug side is at about 11k ohms, also within spec.

I measured the resistance on all 4 spark plug caps and came up with some off numbers. The inside caps were definately higher at 8.7 and 9.1 Kohms. While the outers were at 3.9 and 4.7 Kohms. Would these numbers possibly cause this problem? Do the inner plug caps need to be the 10 Kohm mentioned above and the outers 5 Kohm or all four at 5 Kohm... I can't find spark plug cap resistance specs for the bike anywhere and the manual only lists one resistance spec for ignition coils regardless of which one it is.

 

They should be between 4 and 6 k ohms... if not, they are too high and will have too much resistance. I am currently working with my issues as such with fouling, but also came across the fact that I was sold type R plugs for replacement.. which means I am getting too much resistance through my plugs and probably not getting a good spark for burn. Replace those caps!!!

 

So I replaced the spark plug boots with brand new 5k ohm NGK's

Didn't fix it the problem.

The plugs still foul under stretches of light load/idle

I'm officially grasping at straws.

I'm going to check the compression. I had eliminated this as a problem because of how well the bike runs when it has clean plugs and the fact that it ALWAYS starts right up.

I'm going to pull the carbs off (again... arrrgh!) and go through the enrichment plungers (again... arrgh!) to make sure there is no leakage. The bike always starts easy when it's cold and without any choke, which I've heard is not the norm, so maybe that's the problem. I'm sceptical though, because it seems to run lean under heavy load. Ran the bike at 80 mph/5500-6000 rpm for a couple of miles and did a plug chop and the insulators were bright white. There's plenty of free play in the enrichment linkage so that's fine, but maybe the plunger seats? Does anyone have any suggestions on how to best make sure they will seal perfectly? Is it possible to seat them with a mild abrasive like you would with a valve?

I found a couple threads that seem to have the same problems I'm having but none of them end in a solution... very frustrating... has anyone ever fixed this problem before?

Oh well, wish me luck, I've about had it.

 

On any carb I ever messed with, mixture screws control idle mix ONLY.

That whole circuit is bypassed as soon as the throttle opens.

Either I got some learning to do, or someone's going on an incorrect assumption about how it works...

 

Did you ever CHECK the Value Stamped on the Pilot Jets?

If you are only at a Turn-'n-a-half out. You shouldn't be able to Fire that baby up COLD like you just you just stopped to run-in and pick-up a Lottery Ticket.

Do the Compression Test.
You should have Started with the Compression Test.
Since the Bike would rather run than not ... I'd say those Comp Numbers should be good.

You are Pulling more Fuel than Normal with the Bike cold.
Stuck Enrichments
Wrong Pilot Jets
Misplaced AIR Jets
Diaphragms not returning to the Bottom of travel.

 

@ Rick

The plugs foul cold or hot, temp makes no difference

I have a 195 pilot air jet installed on all 4 carbs. That is spec for the bike (per Len)

The carbs pass the "clunk" test

I'll certainly double check the jet placement when I tear into the carbs, I'm pretty sure they're right unless the manual is wrong.

I'm with you on the runs too well to have lousy compression.

What's got me scratching my head is that all 4 plugs are sooting up. I find it hard to believe that all four carbs/cylinders/plugs/coils could have exactly the same problem... That's why I changed out the battery, it seemed to be the only thing that had low RPM difference and all four cylinders in common... anything else come to mind that would fit that?

I hope the plungers are the answer because I'm out of ideas

 

Funny you should mention it.
The Manual (Haynes) IS wrong.

Here is a photo of how the AIR Jets are supposed to be positioned in the Vacuum Chamber.

Notice how the ORIFICE of AIR Jets are OPPOSITE from Fuel Jets and how you'd think they'd get placed.

Main AIR = o
Main Fuel = O
Pilot AIR = O
Pilot Fuel =o