Complete XJ650 Rebuild

Cases are together and moving on to assembling the rest of the engine.

Got another question for you all and a little update on progress.

Update.
I was putting together the Oil Pump / Filter and the gear that turns the chain was not turning smoothly. So I disassembled it and found out between the screen and the cap of the filter was completely packed with debris and metal shards (from the old engine). Unfortunately I did not get a picture of it but I highlighted the area that was packed with crap. Got that cleaned out and all put back together, everything turning smoothly.


Question.
I was now onto putting the clutch housing into the case and everything goes in very smoothly but this jumped out at me.
The teeth on the housing rub up against case but since it sits around the transmission shaft, I have no room to move it or anything.


Now I looked at the old case where this hosing came from and it looks like it rubbed up against it too.


So I am just curious is that how it is supposed to be or is that something that can be "shaved" down?
Because when I do spin the housing with my hand, it does catch that lip every now and then.

 

It's a tight fit but the basket shouldn't rub the case at all.

Gary H.

 

Been working on a lot of things lately but good news, the engine is complete and everything worked out when checking the timing!

I will update with pictures but I am moving onto electrical and this could be a head ache:/

First thing that jumps at me is the diagram shows a ground wire coming from the Starter Motor.

But I don't see how that is possible. The only Stud coming from the Starter Motor is for the wire coming from the Stater Switch, so where would the ground attach? I do have a large gauge wire that is bolted to the middle-back side of the engine that I have not found where to attach that to yet either.

Outside of that, just mounting and placing all my new things like Turn Signals, Tail Lights, Gauges.

 

There is no ground wire for the starter, it's grounded by bolting to the engine. The electrical schematic just shows that it is grounded.

There are two wires bolted to the back of that motor. One goes to the battery negative terminal and the other goes to the frame.

 

Thanks, That is what I was thinking was going on, but I wanted to make sure incase I was understanding it wrong.

 

I am looking at replacing my Rectifier. Are all of them universal or am I crazy. I have been search a bunch of different sites and when I enter my make and model of bike, nothing comes up but a lot of them list other types of bikes. So I was curious if there are specific ones for different types of bikes or uses?

 

Start a conversation with Chacal. He has the correct regulator in stock. They are not a universal part, even though they all do the same job.

 

Electrical update. I don't have the link but I got a diagram from these forms of "Simple Wiring for Xjs" and I have that complete.
I have my tail light turn on and when I flip the switch to run and click the start button, my starter circuit cut off relay clicks but that is it.

I was expecting to hear something from the stater motor.
Should I here something and if so any idea what is wrong?
I am still in assembly so I don't have any fluids, gas, or carbs on yet:/
I know that sounds stupid but I was thinking I am just trying to get the starter motor to make sound

 

Jump the two post on the solenoid. The starter should spin.

Gary H.

 

I am not an electian but what do you mean jump?:/
I think I know but want to make sure and if so what does that mean for my solenoid?

 

Temporarily connect the two big posts with a conductor, such as a screwdriver, wrench, or quarter.

It's not directly indicative of a solenoid problem but does eliminate or confirm a problem with the starter motor.

If the starter does not spin then you have a starter problem.
If the starter does spin then you need to check for voltage aat the small solenoid terminals when the starter button is pressed.

 

What he ^ said.

Gary H.

 

Alright, so when I jump the solenoid terminals, the Starter Motor does make a sound. But not I am at a stand still:/
If I am understand this correctly, When I hit the switch, the Cut off relay makes a click but the current is not going thru the Solenoid right?

Not sure where to go from here, everything in the diagram is connected except the brake switch.
Could I have my starter wired backwards or something (It is after market and the colors don't match)

 

It's possible but the oe starter only has one thick (+) power source from the solenoid. Ground (-) is through the case/engine. Make sure the (+) power bolt is insulated through the case. Post a pic of the aftermarket starter.

Gary H.

 

Hav you opened the starter?
It is possible to clock the brushes incorrectly and spin the starter the wrong way.

 

That ^ would be my next guess but he said...

What wires?

Gary H.

 

I have to assume that he means the starter solenoid since the starter only has one wire going to it.

 

I apologize guys. When I said starter, I meant switch:/
My RUN/Kill - Start switch is after market and I was questioning if I had that wired incorrectly.

Again, when I jumped the Solenoid, the Starter made a sound and I can see the Crankshaft spin (Pickup Coil spins), so I am hoping that is alright.
I have everything wired like I do in that SIMPLE diagram above. I just don't see a Relay in it, so I am wondering if that is messing me up.
Kinda running off two diagrams The Simple one and the FULL COLOR diagram attached.

So this was a thought that I had, let me know if I am off base.
Since I have the Red/White running through the Relay but NO Clutch Switch (Since that also goes into the relay), could that be messing up my signal to the Solenoid?

Sorry I am doing this without pictures and occasionally using the wrong wording, I know it is making it confusing. Just trying to get a step further each day and this is my only source for answers.

How do I know if I have a Relay wired correctly? I have no diagrams for these little gold boxes.

Tonight I will follow up with some pictures and see if my idea worked.

I really do appreciate all the help, the amount of knowledge I have gained from here is amazing!

 

I think figured out what was wrong with all my starting system and I am embarrassed to say I believe it was due to my battery not having a full charge.

I left the charger on over night and everything seemed to work properly the next morning. I do believe I fried my Starter Cut-Off relay because that does not click anymore. So I by-passed that and I can get the Starer to spin.
So I moved onto my Headlight circuit and hit a road block.

Everything seems to work all the way up to the actual headlight. The terminal that comes from the light (Yellow/ Green/Black) when I plug that in and turn the key, my headlight fuse blows. When it is unplugged I have power running through the whole circuit problem free and I can read 12v at the green and yellow wire prior to plugging it into the actual headlight.

I also checked the headlight manually to make sure it wasn't broken or anything and it works.

I have no exposed wires, I triple checked that. Used two different controls for the LH (old and new) and the same thing happens:/

Any ideas?

 

Update and hoping for some help.

Everything above about my Starter, Solenoid, and Switch. All good
I think It was just me being stupid and not having a fully charged battery, needing to by pass some relays, etc.

Currently when I hit the starter switch, the Starter Motor Turns and I can hear/see the engine turning. I can hear air being pushed through the cylinders, so I imagine compression is doing alright. I was messing around all day with trying to get it started but no luck.

I connected the tank to my carbs and the only time I can get gas to flow is on Prime, nothing when ON is ... well on.
Also I am not sure where this second "out" is connected t0o? The small one on top of the Petcock.


A buddy of mine stopped over and tried to help me out. We figured out my "Left" Ignition coil was a lot hotter then my right one.
Spark plugs from 1 and 4 spark, but 2 and 3 DO NOT. (Which the wires for those are coming from the Left Ignition Coil).

I am just at a cross roads where I have no idea what or where to go. I opened the screws on each Carb bowl and gas is coming out so I believe I have gas in there but is gas supposed to go to anything else in the engine?
My air box is not connected at the moment, I am just trying to get the engine to fire.

 

It's a vac port. There should be a vac hose from the port to one of the vac ports on the intake boots (usually #3).

Gary H.

 

So I am trying to figure out if my ignition coils are bad or not and was reading this thread.
http://www.xjbikes.com/forums/threads/how-to-ignition-troubleshooting.21932/

I tried this test
5a. Switch the Orange and Grey wires from the pickups (6-position TCI plug) at the TCI. If the sparking and non-sparking pairs of plugs swap (i.e. if you had spark on 1/4 and not on 2/3 prior to swapping Orange/Grey and now have spark on 2/3 and not on 1/4) then you've got a bad pickup. If this didn't make a difference, swap the wires back and go to 5b.

And that is exactly what happened. I can get spark on 2/3 after I switch the Orange/RW and Gray/RW (At the terminals coming out of the coils themselves)

Is there anyway to test my Pickup? Replace them or fix them?

 

Also when I do have everything wired correctly the Coil that has the gray wire going into it (2 and 3) it starts to heat up when the key is turned on but the other coils does not.
Out of my TCI box, I get 12V on the orange wire (coming out of the 4-position connector) but nothing out of the gray. Am I supposed to get a reading off the gray?

 

IGNITION PICK-UP COILS:

One of the nice things about the stock XJ electrical systems is the transistorized (maintenance free) ignition systems.......no points to set or timing to adjust (except on 1986 XJ700-X models). All of those dreadful chores are handled for you, automatically, via the IGNITION PICK-UP COILS SYSTEM, and further down the line, via the TCI CONTROL MODULE. These components are generally very reliable, almost to the point of being bulletproof, and as mentioned, are truly "plug-and-play" devices that need no periodic maintenance once installed. However, they are quite susceptible to damage via electrical shorts or voltage surges (i.e. if you jumper the battery incorrectly, etc.).

Checking pick-up coils: the resistance across each pair of lead wires (at the TCI) should be as follows. NOTE: if both coils are out of specifications, suspect a pinched or shorted black ground wire, which is a shared ground for both of the pick-up coils on most models. It is very unlikely (although not impossible, especially in a case of improper jump-starting, etc.) that BOTH pick-up coils would expire at the same time!

A simple test to see if the coils are working, at all is to place a voltmeter (preferably an analog unit) across the Grey or the Orange wire to the Black wire. Energize the system and watch for voltage pulses as you rotate the reluctor past the pickup. This can be done by hand or with the starter.......we'd recommend using the hand method so that the pulses are slow enough to see. These "pulses" are what the TCI "black box" counts and interprets when "deciding" when to fire the ignition coils.

NOTE: the orange lead wire is the trigger wire for the #1/#4 ignition coils, while the grey lead wire is the trigger for the #2/#3 ignition coils.


120 ohms +/- 10% for all XJ650 Turbo models, XJ700 all models and XJ750-X models, XJ900RK, RL, N/FN, and F models, and XJ1100 models.

650 ohms +/- 20% for all XJ550 models, 1982-84 XJ650 Maxim, 1982 XJ650RJC Seca (Canadian, yics-engine), and all XJ750 models.

700 ohms +/- 20% for all 1980-81 XJ650 models and 1982 XJ650RJ (non-yics engine) models.

720 ohms +/- 20% for all XS1100 models

 

TCI UNITS:

Yamaha (thankfully!) used a TCI (which stands for Transistor Controlled Ignition) system on all XJ-series bikes to control the coils, timing, spark advance, etc. A TCI unit is an "early" version of the now-common electronic control systems that are used on virtually all modern vehicles of almost every type, and even these early versions are completely maintenance-free and very rarely cause problems...........which is a good thing, because original TCI boxes are no longer available new.

When engine performance problems develops, many people immediately suspect that the cause may be within the "black box" workings of their TCI unit, which is unlikely. The factory service manual gives "instructions" for diagnosing TCI problems, and it basically says "test every other possible cause for your problem and if no other cause for the problem exists, only then should you "suspect" TCI failure, but before you buy a replacement, first try to find a known, working TCI unit from a similar bike and plug it in on the problem bike, and see if the problem goes away............"

Well!

There are three main problems that TCI units succumb to after years of reliable service:

1) bad solder joints on some of the internal components (known as "cold solder joints") result in the component pieces coming loose from the circuit board, and thus they can no longer perform their function reliably (or at all).

2) component failure......a blow-up transistor, a burned circuit trace, etc. This situation can develop if you have a short-circuit in your electrical system, or hook up your battery or jumper cables incorrectly, etc. TCI units do not like "big blue sparks" in the electrical system (except at the spark plugs, of course!).

3) another common failure of these units occurs if the TCI is continuously grounding the ignition coil (i.e. its output driver is shorted). You can verify this situation with an ohmmeter with the following tests:

- disconnect the 2-pin plug at the ignition coil and measure from the orange or grey wire to the chassis. You should see very high resistance. This should be pretty close on both the working and non-working channels.

- if you read a few ohms of resistance or less, then the TCI is bad. A shorted driver will also make the ignition coil run very hot and may ruin the coil.

4) dirty external terminal connections.


Bad solder joints can be repaired by someone who is skilled at that sort of diagnosis and repair, and even individual circuit components can be replaced, but it's tough to find someone in the modern world of "pitch-and-plug" skill-sets who actually has the skill and patience to do this type of work. Yamaha gave absolutely "zero" electrical specifications for checking the condition of the TCI units, besides the afore-mentioned "check everything else first" type of diagnosis.

But you can perform a simple set of tests to determine whether your TCI unit is good or not, without having a second, known good unit to install in place of the suspect unit. Although these instructions were written for XS owners, the exact same thoughts apply to the TCI units on the XJ-series of bikes:

http://www.xs11.com/forum/showthread.php?t=38224&highlight=tci+repair

The above is stolen, borrowed or even plagiarized from Randy Rado's site before it went away. It does require an analog meter as digital multi-meters do not show the swing of the needle that is required to test it.

"Using a voltmeter set on 12VDC, connect the positive meter lead to the Orange or Grey coil lead at the TCI. Connect the negative meter lead to the black (negative) lead at the TCI. Turn on the ignition. Voltage should come right up to about 10 - 11VDC. Crank the ignition and observe the meter. Look for a wide voltage swing during cranking. A strong swing indicates that the pickups and TCI are working OK and your trouble is between the TCI and the plugs. Possibly a bad ballast resistor, bad coil, bad plug cap or just corroded connections. Repeat this test for both Orange and Grey coil leads."

All of the XJ-series TCI units are of the "4RO" style as described in the above article.

Video here:

http://s307.beta.photobucket.com/us...4.html?&_suid=1354140627504033601775276167517


And if the above isn't enough, if you feel the need to get medieval with your TCI unit, well, then it doesn't get much better than this:

http://www.jetav8r.com/Vision/IgnitionFAQ.html


By the way, the TCI needs a minimum of about 10VDC to operate………and while the starter will spin the engine over like mad with low voltage, the TCI falls on its face at less than 10 volts…which can lead to all sorts of confusion when a battery low-voltage condition occurs!.

 

IGNITION COILS AND RELATED:

OEM and aftermarket IGNITION COILS replace damaged, cracked, or out-of-spec originals to help "light that XJ fire" under your...well, you know. Twenty-plus year old original coils can suffer from a variety of ailments that prevent them from doing their job, including burned or shorted internal windings, hairline cracks in the outer cases, or damaged and destroyed plug wire leads.

NOTE: although all of the following is repeated below under the spark plug Caps section, it would be good to review it here, also. ALWAYS TEST YOUR COILS (as described below) BEFORE ASSUMING THEY ARE THE PROBLEM. AND ALWAYS TEST YOUR COILS IF YOU ARE HAVING MIS-FIRING, FOULED PLUGS, OR OTHER (POSSIBLY) IGNITION-RELATED ENGINE PERFORMANCE PROBLEMS.

This will save you an incredible amount of time, effort, and $$$ and give you more quality riding time as opposed to a greater quantity of diagnostic time!


And a final note: using hi-performance, aftermarket coils (like Dyna or Accel brand) will generally NOT "improve the performance" of your bike in any measurable, meaningful way if your factory coils are performing okay. But if your factory system (coils, plug wires, and plug caps) are not up to snuff, then certainly ANY replacement (stock or aftermarket) coils are going to eliminate such problems and "improve performance". Be aware, though, that aftermarket coils can take quite a bit of mounting bracket fabrication efforts to make them fit properly into these cramped XJ frames, and you will have to purchase the plug wires, boots, and caps separately also.



Checking Factory Coils:

Factory Yamaha coils need to "see" a total load resistance on the secondary side (the "going-to-the-plugs" side of the coil) 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, ambient temperature, etc. etc. All readings are specified at 70-F.

In any case, all factory XJ coils and wires combined---BUT WITHOUT THE CAPS OR PLUGS ATTACHED---have the following primary and secondary resistance ranges:


For all XJ models except XJ700, XJ750-X, and XJ900 models:

Primary (input from TCI): 2.5 ohms +/- 10%
= 2.25 ohms - 2.75 ohms acceptable range

Secondary (output to spark plugs): 11K ohms +/- 20%
= 8,800 ohms - 13,200 ohms acceptable range


For all XJ700 and XJ750-X models:

Primary (input from TCI): 2.7 ohms +/- 10%
= 2.43 ohms - 2.97 ohms acceptable range

Secondary (output to spark plugs): 12K ohms +/- 20%
= 9,600 ohms - 14,400 ohms acceptable range


For all XJ900RK, RL, N, FN, and F models:

Primary (input from TCI): 2.7 ohms +/- 10%
= 2.43 ohms - 2.97 ohms acceptable range

Secondary (output to spark plugs): 13.2K ohms +/- 20%
= 10,560 ohms - 15,840 ohms acceptable range


For all XS1100 models:

Primary (input from TCI): 1.5 ohms +/- 10%
= 1.35 ohms -1.65 ohms acceptable range

Secondary (output to spark plugs): 15K ohms +/- 20%
= 12,000 ohms - 18,000 ohms acceptable range




All models:

Voltage at coil positive input terminal (the red wire with the white tracer stripe) with the engine running: 12+V This measurement should be taken at the back of the connector shell (stick the volt meter probe in thru the back of the connector) and the battery negative terminal. Compare this reading with the measured battery voltage (voltmeter connected between the battery negative and the battery positive terminals). Any significant difference or lack of voltage indicates corroded or broken connections in-between the fusebox and the ignition coils, and reduced voltage at the coil input will result in reduced coil output (at the spark plugs). Although reduced voltage input (and thus less coil output voltage) may not significantly affect engine performance once the engine is warmed up, it can and will result in "hard start" situations when the engine is cold and/or when the choke system is engaged (since richer fuel mixtures require a much stronger spark to create ignition of the fuel mixture).



In order to help diagnosing engine performance problems that seem to be "plug-related", always measure the resistance of your coils, both primary and secondary sides, as well as the voltage at the coil input (primary) "hot lead" (the red/white stripe wire) before you start replacing parts. 20+ year old coils can and do fail regularly. If you need to replace your coils, and decide to buy used, original coils "sight unseen", always make sure that the seller checks them for you before you buy them!

 

Sorry I did the earlier post a little backwards...

5a. Switch the Orange and Grey wires from the pickups (6-position TCI plug) at the TCI. If the sparking and non-sparking pairs of plugs swap (i.e. if you had spark on 1/4 and not on 2/3 prior to swapping Orange/Grey and now have spark on 2/3 and not on 1/4) then you've got a bad pickup. If this didn't make a difference, swap the wires back and go to 5b.
This didn't make a difference

5b. Switch the Orange and Grey wires from the coils (4-position TCI plug) at the TCI. If the sparking and non-sparking pairs of plugs swap, then you've got a bad channel in your TCI. You'll need to replace the TCI or get it repaired.
The plugs swapped here

I have tried to filter through all that info you just posted and I am completely clueless:/
I am afraid to buy another TCI if that isn't the problem but I am pretty sure after everything I have crossed, is the problem. It worked when I bought the bike 2 years ago. My fear is ruining another one:/

Is it possible to check my current one or have someone repair it?

 

On top of that I tested the Primary sides of both coils, I got 3.5ohms on both but the secondary side I can not get a reading on either coil (even though one is sparking and the other is not)

 

Way out of spec............they may still work, but will be weak.

Did you remove the plug CAPS before testing?



Typical things that fail (in order of failure prevalence):

a) spark plugs
b) plug caps
c) ignition coils
d) harness connectors
e) pick-up coils
f) TCI

 

Yea, removed the caps, same reading.
Just completely lost right now.
Orange wite reads 12v coming out of the 4 prong connector, gray reads nothing.
When the orange is plugged into a ignition coil, sparks show. Gray nothing.
When I switch the orange and gray wire at the 4 prong harness. I get the opposite.

So I feel like the tci is not sending power Out of the prong where the gray is supposed to be to the ignition. Or the pickup is not sending signal to the tci (gray)?

 

You won't see 12V from the TCI consistently unless the engine is running, and you should not test for voltage at the primary coils with the engine running or TCI damage can result.

 

Yes, sounds like one or the other or a bad harness connection/broken wire/etc. Start with continuity checks between wire connectors on the gray wire to make sure it's not a (simple) problem. Should have continuity from:

a) the TCI output to the ignition coil connector
b) the pick-up coils to the TCI

Assuming those tests pass, then check the gray-wire pick-up coil resistance as described above.

If it's okay, then either replace the TCI box or, if you're in the mood, take it apart and see if you can visually see any problems on the circuit board.

 

The engine hasn't started or isn't running. So hopefully nothing is wrong with the primary coils.
But why am I reading 12v at the orange out of the tci and that is the coil that is sparking?

 

The TCI is responsible for grounding the coil primary side, the +12V (key on) is fed on the Red/white tracer stripe wire. On the orange (or gray) wire, you can only measure 12V when that coil is being grounded, and when the engine isn't running, the TCI should not be grounding either coil but for an instant.

The orange (or grey) wire is not the "hot" wire to the coil primary side. They are the "ground path's" for the 12V that comes into the ignition coils from the battery.



IGNITION SYSTEM OVERVIEW:

Before we get into the list of components within your ignition system, it may be useful to explore the basics of the ignition design used on these bikes, as this knowledge may help you to better recognize, troubleshoot, and repair performance problems with your engine that you think may be due to these components.

The ignition system actually begins at the left end of your CRANKSHAFT, since the rotational position of the crankshaft determines the position of the pistons and of the camshafts. Obviously, since the purpose of the entire ignition system is to deliver a high-voltage spark at the plugs at exactly the proper instant----meaning, as the piston approaches Top Dead Center of the compression stroke----then the ignition system must "know" what the position of the crankshaft is in order to transfer that information (via electrical signals) to the major components: the PICK-UP COILS, then onto the TCI UNIT, to the IGNITION COILS, via the PLUG WIRES and through the PLUG CAPS and finally, onto the SPARK PLUGS.

But it all begins at the crankshaft, which has a flat metal ROTOR DISC bolted onto the left side snout, and which hides under the left side, round "Oil Pump Cover" (also called a "YICS" cover on YICS-equipped engines). This spinning rotor disc has a small magnet embedded within it's outer tip, and as that outer tip rotates past the fixed magnets within the PICK-UP COILS, the interaction of magnetic fields triggers a small voltage in the pick-up coil wires that lead to the TCI UNIT.

Note that since the rotor disc is fixed in position and spins along with the crankshaft, this rotor disc "knows" the position of the crankshaft at all times. And since the pick-up coils are bolted in place, and are thus stationary, whenever the spinning rotor passes by a fixed pick-up coil, and thus triggers it to send a voltage signal to the TCI, in this way the TCI unit thus also "knows" where the crankshaft is, rotationally-speaking, and thus where the pistons are in relation to Top Dead Center and when their spark plugs need to be fired.......

Also note that since there are only two pick-up coils for your four-cylinder engine, that each pick-up coil is actually providing the "firing signal" to the TCI unit for two different cylinders. In these engines, one pick-up coil is responsible for sending the signal to the TCI that eventually leads to the spark plugs firing off for cylinders #1 and #4 at the same time, and the other pick-up coil sends the message to the TCI unit to fire off spark plugs #2 and #3, again, at the same time.

Although this may seem odd at first, the mechanical arrangement within the engine of the crank throws, and thus the rods and pistons, as well as the camshaft timing, allow this situation to proceed without a problem; in fact, when one of these "paired" cylinders (for example, #1) is approaching Top Dead Center of it compression stroke----and thus is in need of a spark from its spark plug----it's "mated" cylinder (#4) is also approaching Top Dead Center, too.........but on its exhaust stroke.......and so even though cylinder #4 gets a spark at its spark plug, there's nothing in the cylinder to combust, and thus it's a "wasted" (yet harmless) spark that occurs in cylinder #4.

Obviously, the exact same situation occurs in the mated pair of cylinders #2 and #3.

In fact, the whole system is known as the "wasted spark" system, since one of the two sparks that always occur at the same time is "wasted" on a cylinder that is on its exhaust stroke............


Anyway, to continue our journey: when a pick-up coil is energized by the passing magnetic field of the spinning rotor disc, it send an electrical impulse signal to the TCI. Therefore, the TCI unit now also "knows" the position of the crankshaft (and thus of the piston). Using other sensor information.....primarily, the rotational speed (RPM's) of the engine......the computer chip in the TCI is then responsible for calculating exactly when to send a "message" to the proper IGNITION COIL to release it's energy to the proper cylinders. And note that we said "cylinders" (plural), since just like the pick-up coils, one ignition coil also sparks two cylinders at once (part of the same "wasted spark" method discussed above).


The ignition coils use a rather small (12V) input on their primary side to product a large (20,000V +) amount of electrical energy on their discharge (spark plug wires). When the TCI unit determines that "the time is right" for a particular coil to fire, it grounds that coil, which collapses the small magnetic field inside the primary side of the coil, which thus induces a large electrical field in the secondary (plug wires) side of the coil, which then rushes to ground. This electrical energy rushes down the non-resistive PLUG WIRES, through a resistor in the SPARK PLUG CAP, and finally jumps a small gap in the spark plug electrode on it's way to ground, and thus the spark occurs that fires the air-fuel mixture (in one of the two cylinders being sparked at the same time), things go boom, power gets produced, and you're on the way down the road........




Why does my engine sometimes backfire when I first turn on the key (without attempting to start the engine)?:

- When you kill the engine, the intakes will still have some remaining (un-burned) air-fuel mixture remaining in them. Upon powering up the bike (turning the key on), the ignition system will apply 12 volts to the coils, thus charging them. Of course, that constant current is not good for the coils, so few seconds later (if the engine is not started) the TCI shuts down the coils by grounding them (to protect the coils from overheating) which cuts the current to the coils and thus triggers a spark to the plugs. If there is enough un-burned fuel in the intake manifolds or the combustion chambers, and if the valves are held open by the camshafts, a backfire thru the exhaust header and/or thru the intake manifolds/carbs/airbox can result.


Why does my engine sometimes backfire when I first turn on the key (without attempting to start the engine)?:

- When you kill the engine, the intakes will still have some remaining (un-burned) air-fuel mixture remaining in them. Upon powering up the bike (turning the key on), the ignition system will apply 12 volts to the coils, thus charging them. Of course, that constant current is not good for the coils, so few seconds later (if the engine is not started) the TCI shuts down the coils by grounding them (to protect the coils from overheating) which cuts the current to the coils and thus triggers a spark to the plugs. If there is enough un-burned fuel in the intake manifolds or the combustion chambers, and if the valves are held open by the camshafts, a backfire thru the exhaust header and/or thru the intake manifolds/carbs/airbox can result.

 

Chacal, as always, you are a source of great knowledge about our XJ's. It is nice because other sites you only get 'general' knowledge about motorcycle maintenance. Here you give bike specific info. You must really have a lot of experience with these bikes.

 

I agree, the information I have collected from this site has gotten me quite far with a complete rebuild of my bike. I would of thrown this bike in the trash if I didn't find this site. Everyone here who answers and helps are key.
The information can be overwhelming but each day I read over stuff, it clears itself up and makes more sense.

Tonight I am tracing my gray wire to see if there are any breaks I can't see and also checking the black from the pickup coil. Since both ignition coils do fire (when my working orange wire is attached either of them) I am trying to eliminate the pickup before I get a new tci box.

 

So tonight I got home and checked a few things which I believe is telling me it is the tci module.

I checked the Ohms on the pickup coils from the adapter that enter the tci from the pickups and from the adapter from the ignition coils. That way I could tell if there were any "breaks" in the wires going to either.

Black and Gray then also Black and Orange from the pickups both read about 630 Ohms

The I tested the Red/White and Orange then also the Red/White/Gray going to the Ignition Coils and again both read 3.5 Ohms (I did this before from the terminals coming right out of the coils but this time was from the "4-prong adapter" going into the TCI). Same reading.

The I plugged everything as it should be, turn the key, hit start and I got spark on 1/4 but not on 2/3.

The I took the Orange and Gray and changed the placement of those wires (Coming out of the TCI to the Ignitions Coils), then got spark on 2/3 and not on 1/4.

So unless I am missing something I have to blame this on the TCI, right?

 

Outside of my electrical situation I am dealing with. This is where I am at with the bike
I know my electrical looks like a mess but I assure you I have checked it 6 times and getting read to wrap it up to make it cleaner. All connections are clean, I just left it open to diagnose as I move thru everything. The only thing I do not have working at this point is the Headlight/Brake light/Turn Signal circuit (from my understanding, requires the engine to be running for that to work.)

Looks pretty
Juts need her to run.

 

Update
Got a new TCI yesterday and all 4 plugs are firing! Problem is still not starting.

I got a compression gauge and my readings are as follows
1 - 40 psi
2 - 0 psi
3 - 0 psi
4 - 50 psi

That seems very off to me given the fact that I checked all my valves twice when I was putting the engine back together.
Could it be as simple as checking them again?
I just don't get why my 2 and 3 would have no compression what-so-ever. Or my compression gauge isn't working:/

Another strange thing that happened was since I have been trying to start this, my timing plate was spinning sort of slow when I hit the start button. Now all of a sudden this morning it spins a lot faster. I didn't change anything, it was just something I noticed this morning, maybe it was doing it all along.

 

I would start with trying another gauge or testing yours on a running engine to see if you get higher numbers. Out of spec shims would rarely give you 0 PSI, the valves would have to be open quite far.

Were the cams timed in properly? I would look at that first. Easy to check the alignment marks.

Head gasket? There were a couple instances of the cam tunnel gasket being too thick and causing the head gasket to not seal between 2 and 3. I had this happen.

Bent valves? It's possible to bend a valve when assembling/checking clearances as these are interference engines. I haven't bent one but from what I've read in other posts where members have, it doesn't take much force and you really don't feel it.

 

I timed the cams 3 times. The first time I was slightly off. I did it again and was dead on after 10 rotations. But defiantly the first thing I am going to check tonight.

This makes sense why 2/3 might be that way. I torqued everything to spec when I was assembling but again. Something to check if the everything else comes out.

This might be a dumb question but what about the YICS end plugs? I just realized mine are not on right now. Could that be giving me the readings I am getting?

 

Won't affect your compression numbers but will keep it from running well!

 

+1. The YICS passages terminate in the intake ports, before the valves. Leaving the end plugs off is creating the same effect as uncapping the vac ports on the intake boots; a big vacuum leak.

 

I ended up shooting about 20psi of air into cylinder 2/3 and could feel air coming out the center front of the engine, roughly where the cam chain is.
Got a new, different cam chain gasket from Chacal. He said that might be my problem why I couldn't seal and was causing the zero compression at 2 and 3.
Gonna do that this weekend and hope that is my solution. Also hoping that means it wasn't a problem with my timing or any of that (so far).

 

Same problem I had, did you get the OEM one this time?

While the head is off, you can check your valves by filling the combustion chamber or ports with paint thinner and seeing if you have any seepage. This way you know its good and you won't be pulling the head a third time.

 

She f*ucking runs!!!!!

Sounds so good.
Revs extremely hard but I put individual pod filters on and I believe I need to adjust my jets. I could put my hand over the intakes and control how it idles. Any thoughts?

Main thing is the engine works now on to tuning!
Again thank all of you for assiting me through this. Still a bit to go but I am very happy my engine runs.

 

Pods will make the bike run lean, and have a flat-spot inthe midrange. Yes you will have to rejet. Start with two sizes up on both the pilot and main fuel jets. You'll have to live with the flat spot though.

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The only thing controlling fueling off idle is the differentce between engine vacuum and atmospheric vacuum. Anything that messes with airflow through the carbs affects how the slides move.

 

Rejetted my carbs and getting the same thing. I even tapped up my pod filters just to see if I "closed" if I could get any sort of change with the high rev on start.
Nothing.

I have been reading that I might have a air leak on the throttle side of the carbs, somewhere around my intake manifold boots? I have brand new ones installed but maybe I didn't pay enough attention to the sealing of them when I put them on. I am going to check them tonight and see if that is where my problem is coming from but does anyone have a suggestion on helping make that seal better on top of new gaskets?
Possibly using Gasket sealant or anything?

It starts fine, just trying to get it to hold an idle so I can adjust everything else. The exhaust get extermely hot and I don't want to leave the bike idling that high for too long.

 

Spray the boots with starting fluid while it's running, that's how I identified my leak.

You should have a fan blowing on the front of the motor while running stable. I was lucky to trash pick a 24" industrial "cage" fan that was just missing the switch. I use that for my tuning sessions.

 

Ran across this over the weekend

I think it is supposed to go inside the cover for the Clutch, I think it is part 24 in this picture


Can anyone confirm this and how it goes in there?

Update on the bike though!
Got it outside and rode around on it for a bit, I have been messing around with the carbs these past few weeks and have gotten a lot closer which I will update.
Gonna be following up with some questions on it in the next day or 2.