Noticed difference in engine sound...

Quick list..
Valves in spec
carbs completely tore down, cleaned and rebuilt.
good on vacuum sync and colortune.

Bike idling @1100 rpms..

been this way for 2 months, about 4 tanks of ethanol free gas.

The other day the engine sounded different on acceleration.
Bike seem to drag below 1100 rpms coming to a stop.
From a standing start, bike seemed to hesitate on acceleration.
Exhaust temp on # 1 is 50 degrees below the other 3.
Fuel drains from #1 bowl through bowl drain when opened.
Spark plug tip and insulator are black.

Any ideas on which direction to go?

 

Sooty black, or oily black?

Recheck #1 with your colortune and see if the idle screw may have moved.

 

Hard to tell, definitely isn't a hot dry, but not visibly "wet". I guess that would be sooty...lol...friggin deductive reasoning....lol

I planned on rechecking with colortune and vacuum sync this weekend when I have time.

 

Check the FUEL LEVEL in carb #1.

 

Aww..means removal of carbs...

Figured as much that it would come to this...

If float levels are good, any other ideas before reinstalling carbs?

 

You don't remove carbs to check fuel level - do it on the bike. #1 is one of the easy ones to get to too.

 

I understood to check the float level that the carbs had to be level.

I'm not sure how to check the fuel levels with the carbs on the bike.

Is there a different procedure?

 

Connect a length of clear tubing to the fuel drain, and use it like a spirit level. With the drain screw open you will see what the fuel level in the carb is.

This pic is of a Virago, but it illustrates the idea.

 

Well, you have to prop the front of the bike up so that the carbs sit level, and make sure it's level side-to-side, and then yes, you can check them on the bike.

Yamaha goes into great detail in the factory book explaining a way-too complicated procedure for checking the side-to-side level. Use of a couple of small carpenters' torpedo levels makes it very easy.

 

Bruce,

After checking the carb levels, you may want to look into an ignition misfire on that cylinder. An occasional weak, or no spark, will leave the plug black and sooty. Exhaust temps will also be lower on the one misfiring as it will not burn the fuel/air and create heat.

Start with the basics. Replace the plug, and twist on a new plug cap (after trimming the wire back a 1/4" or so). If that doesn't do the trick, check the coil resistance and condition of the plug wire.

Tony

 

Even more basic than that: ensure the resistor core inside the spark plug cap hasn't simply worked loose.

 

dang it to have to work all day..

I would be surprised if it has anything to do with the carbs. I spent 2 months on this set getting them as new as possible, but ya all know Murphy's law.....

I did remove the spark plug for inspection and reattached the spark plug wire to the plug and you could hear and feel it attach securely to the plug. That didn't make a difference to the #1 cylinder.

I am going to pick up another set of plugs on the way home.

Think I will check the spark with a colortune first, then fuel levels, then new plugs and see what happens.

If that doesn't work, then the question would be ignition? I can only assume since the other 3 cylinders are firing that it would be the spark plug wire or the cap?

 

okie dokie...

fuel level checks,

got new plugs and started the bike and measured the exhaust temps as the engine warmed up.

#2 & 3 warmed up to 117 degrees while 1 & 4 measured at 91 degrees.

Is my thinking correct that it may be coil related?

And I have a cheap multi meter but really don't know how to use it if someone could walk me through the procedure of checking the coils...

Thanks...

 

Popping the plug cap off and on wasn't what I was referring to. INSIDE the plug cap, the resistor core screws in. It may be snapping on and off the plug nicely and still be loose.

Look inside the plug cap. There are screwdriver slots on either side of the hole the tip of the plug goes into. Ensure the core is not loose within the cap.

 

I looked inside all the caps and none have screws. Must not be oem, but they are not new by any means.

 

The Inside of a 1982 XJ750J Maxim #2 & #3 ignition cap:

The Cap, metal slotted contactor, the resistor, round metal contact, & the spring.....

#1 & # 4 caps are not slotted for disassembly......not sure why....

 

I just went out and double checked, .# 1 and #2 do not have slots in them. So am I back to checking the coils?

 

All the OEM plug caps have slotted screws the hold the resistors in place. Not all aftermarket resistor plug caps are rebuildable, and not all plug caps are resitor caps. Use a meter to check the resistance.

From Chacal's catalog:

Sparks Plug Caps:

pc2) Original TD (Tokia-Denso) and aftermarket NGK SPARK PLUG CAPS are available in a variety of styles and configurations. All plug caps include their weatherproof upper and lower rubber end boots.

Okay, before we get going, let's quickly review a little bit about the original Yamaha COILS, PLUG WIRES, PLUG CAPS, and the SPARK PLUGS used on these bikes:

Factory ignition systems are designed to operate properly with a total system resistance on the secondary side (the "going-to-the-spark-plugs" side) of the coils of around 20-30K ohms (ohms being a measure of electrical resistance). Electrical resistance depends on a number of factors: wire size, type of material, length of material, age of material, ambient temperature, etc. etc. In any case, most factory XJ coils and wires combined---BUT WITHOUT THE CAPS OR PLUGS ATTACHED---are specified to have a resistance of around 11K ohms, +/- 20%, at 68-degrees Fahrenheit. Please see the complete list of specifications in the "COILS" section above.

Plug WIRES on factory coils are non-replaceable, at least not without a bit of surgery. Suffice it to say that if your coils measure out of specs for resistance (as described above), they're junk and should be replaced, either with another factory coil or a pair of the HCP245 Dyna aftermarket coils.

We do offer an NGK plug wire in-line splicer (HCP2789) that will allow you to cut off and remove a bad factory wire and replace it with a length of our aftermarket plug wire.

The original spark plug wire resistive CAPS---mistakenly called "boots" by some people---are the hard plastic insulators that fit onto the spark plug threaded stud, and accept the plug wire from the coil on their other end via a simple "twist-on" method------yes, the plug wire end of the cap has a metal screw that bites into and "screws" onto the end of the plug wire, penetrating the plug wire inner copper core and making a mechanical connection.

Plug caps use a small internal ceramic resistor, and the resistance of each cap should be checked with an ohmmeter on a periodic basis. Caps that are +/- 20% resistance from specified levels are considered bad, and should be replaced.


A variety of different size and shape plug caps are listed below, in both their original Tokai Denso brand and replacement NGK brand. The replacement NGK caps come in a variety of original configurations and can be safely used to replace broken, missing, damaged, or out-of-spec original caps. And all original and replacement caps will accept up to 8mm spark plug wires easily.

NOTE: all original and replacement spark plug caps are designed to be used on spark plugs that have their screw-on threaded stud topper removed. And while all of the NGK replacement plug caps are specific to either the 12mm plugs (all XJ550, XJ700-X, and XJ750-X models) or the 14mm plugs (all XJ650, XJ700 non-X, all XJ750 non-X, XJ900RK, and XJ1100 models), the original Tokia-Denso plug caps can be fitted to either 12mm or 14mm plugs, so that XJ550 caps can be physically fit upon XJ650 (etc.) engines, and vice-versa.


It is important to remember that you should strive to keep the ignition coil secondary circuit (plug wire, plug cap, and spark plug) total resistance as close as possible to original specifications, which are:

- 15K ohms per cylinder on all 1986 XJ700-X, XJ750-X, and XJ900 S/SH models.
- 10K ohms per cylinder on all XJ550, 1985 XJ700-X models, 1986 XJ700 non-X, XJ750RL, and XJ900 N/FN and F models.
- 5K ohms per cylinder on all XJ650, 1985 XJ700 non-X, all 1981-83 XJ750 models, XJ750-D, XJ900RK and RL models, and XJ1100 models. Although some manuals may call for a different resistor rating on inner vs. outer caps, we've never seen such a combination on an actual bike.


For people who wish to rebuild their otherwise usable original Tokia Denso plug caps, we offer replacement resistors in either the 5K or 10K versions, or non-resistive (0 ohms) replacement rod. Owners who wish to use non-stock spark plugs (such as the popular NGK Iridium plugs or any other replacement plugs) will need to make the appropriate reduction in the secondary circuit total resistive load, which is most easily achieved by reducing the resistance of the plug caps by 5K ohms from their stock specifications.

Just remember to add up the resistance of your plug wires (original wires and all of our replacement wires are 0K ohms, non-resistance wire), the spark plugs (0K for non-resistive plugs, 5K for resistive plugs), and of your plug caps (which can be varied as outlined above) to arrive at the correct total resistance value for each plug!

EXAMPLE: 1982 XJ650 Maxim models originally used the HCP1292 non-resistive (zero ohms) BP7ES spark plugs, along with 5,000 (5K) ohm plug caps on each plug. If you substitute a resistive plug (such as the HCP1293 Iridium plugs, or any other resistive plug) for the original non-resistive plug, then your spark plug + plug cap total resistance will increase from the original 5,000 (5K) ohms to 10,000 (10K) ohms. Therefore, you should reduce the resistance in the plug cap to zero ohms to keep the system at the same total resistance levels as original.


The key to remember is that you simply want to maintain the TOTAL system resistance at whatever the factory rating is. You can't do much about what the coils themselves are rated at, so outside of the coils, you have three choices of where the resistance can be added:

a) the plug wires
b) the plug caps
c) the plugs

For example, the XJ550's require 10K (10,000) ohms of resistance in each wire/cap/plug circuit (outside of the coils themselves). You can achieve this 10K of resistance thru any combination of component pieces; however, it may be simpler to use zero-resistance wires, and then use either:

1) 10K plug caps and 0-ohm (non-resistor) plugs (this is the method that was originally used). This is achieved by using new factory plug caps (which are 10K ohms) or rebuilding the stock plug caps (if you have the originals) with new 10K ohm resistors.

2) 5K aftermarket NGK plug caps and 5K aftermarket resistor plugs.


And finally, always check, with an ohmmeter, the coil primary and secondary resistance, your plug cap resistance, and your spark plug resistance and condition before you start "throwing money" at engine performance problems that seem to be electrically-related!

 

K-Moe,

My caps are original and #1 & #4 are not slotted....is that odd ????

 

Not necessarily. Having done production work at a factory, I can say that sometimes you put a product together with the parts the are on hand. That may have hapened to your bike.

Since you've had it from new, was it ever in a shop for any reason?

The important part is that the caps be resistor caps and of the correct value. Measure the resistances with a meter. Resistors can change value over time.

 

Replacement Resistors for Original Tokia Denso Spark Plug Caps:

If you would like to keep your (otherwise) good condition original plug caps, you can rebuild the ones which are marked TD-131, TD-135, and TD-140 (the TD-133 caps can be rebuilt, but we do not have the correct 5K ohm resistor to fit it, and the TD-134 caps cannot be rebuilt) by replacing the internal RESISTOR CORE, the thin resistor SPRING SEAT DISC, and cleaning the TENSION SPRING and the screw-in brass cap PLUG.

Always remember, that if you replace an original resistor with a core of lesser-value resistance, you should "make-up" the difference in electrical resistance via the use of resistor plugs.


And here's the OEM plug cap scorecard:

T135 (or TD135) XJ550 outers and 900 all positions
T131 (or TD131) XJ550 inners

TD140 XJ700X and XJ750X all positions

T134 (or TD134) XJ650/XJ700/XJ750 air-cooled/XJ1100 outers CANNOT BE REBUILT
T133 (or TD133) XJ650/XJ700/XJ750 air-cooled/XJ1100 inners

 

In what order does the rebuild go: I don't remember.......Took both T-133 apart & can't remember the order....a senior moment...

Do you drop the resistor core in first, followed by the tension spring, followed by the spring seat disc, and finally the brass cap plug ?

On my 1982 XJ750J Maxim

Outers #1 & #4 are TD T-134 Non Rebuildable

Inners #2 & #3 are TD T-133 Rebuildable

 

Solved:

Followed the Ignition troubleshooting write up http://xjbikes.com/Forums/viewtopic/t=21932/.html

Found nothing wrong and all readings are within spec.

Removed carbs....

Removed #1 enrichment circuit plunger. Had some type of buildup on the end of the plunger. Polished with a dremel, cleaned the carb seat. Did this to the other 3 carbs since it was on the bench, although the other 3 looked good. Reassembled and took the bike out for a 20 mile ride.

All cylinders firing like they should, and now it sounds like it should and better yet, runs like it should.

Thanks everyone for your help.

We just keep increasing the knowledge base every day!!