XJ900 #1488

Thanks to the forum folks and pointing out that I had one almost in my backyard. I now have a XJ900. On the table with a charger on it.

xj900 by Tim Brown, on Flickr

Looks like the normal stuff with all out XJ bikes., oil window is full to the top, guessing gas in oil. I will give it a oil change in the morning and a quick look over and see if she will fire up.

 

It's got the side scoops!

 

Good rainy day to work on the bike. Started with an oil change. Forgot how stuck that 19mm oil plug could be. Got it without stripping it. The oil was full of fuel. I looked at the new looking petcock and noticed the PO had on PRI. Was thinking that te petcock was done but not for sure. I did like the little tie warp that was in place instead of a clamp for the petcock hose.
petcock by Tim Brown, on Flickr

Pulled all the plugs, all of them were very "used" but noting too bad. Maybe running rich, but with that nasty air filter, that alone could do it. Put some Blaster in each cylinder just in case and let it soak. Went for the timing cover next, just to see if I can hand turn the motor and it is free. Last person working on the bike must not of had a 19mm wrench.
vic by Tim Brown, on Flickr
From what I can tell that looks like vic grip marks on that bolt. Oh well.

Batter is a newer batter and took a good charge over night. Got some new oil in it and hooked a AUX fuel to it. A little choke, and it more or less fired right up. Fuel was coming out of #4 but not crazy. Turned off the fuel and got the fan on the bike and let it run until it was more or less out of gas.

Stared prep for pulling carbs, man they sure made the XJ900 for pulling the carbs. Really short boots on the air box side, very nice. Just pushed them back into the air box and the carbs popped off with a little nudge from both sides. I did notice this and will have to get a OEM one to replace, yet another tie wrap.
Tie rap by Tim Brown, on Flickr

Carbs took a while to get cleaned up and found that I need some new bowl gaskets for sure. But being that these carbs go in and out with ease, I had to put them back in and start the bike up. Only thing in the carbs that were bad were the emulation tubs. Most of the holes were plugged. The rest of the carbs were good, but the bowls were showing signs the tank needs some TLC.

Checked the charging system, looking good. Once I moved the wonderful old bus fuses around a little bit, all the dash and headlight stated to work. Seems that the bike is ready for the road test once I get some new gaskets installed. I did the brake flush too and that was more or less easy. The front was not so easy, as all the bleed screws were plugged with rust and stuff. All good now. Ended up getting some air in the line, took a while to get pressure back up.

 

Always fun to find all the little Easter eggs left by the PO.

 

Need to order a few parts. Rebuild front brake MC, it is leaking. Bowl gaskets, only one leaking #4 but get one get all 4. I also think #4 float needs to be adjusted. Throttle cable is working, but the 90 degree protector that is held in place by a screw and bracket is broken. Very common to have these broken there. The Vision 550 I just refreshed had the same thing.

Got the gas tank soaking for a week in evaporust. Temps are still only in the 50s here, the process should be done in 70 or above temps. We will warm up later this week, that will help take care of the spot rust in the tank.

Cleaned the petcock, looks to be new or almost new and have very little issues or gunk at all. Just hope it works as it should. I normally change them over to a non vacuum type just to take that potential issue out of the equation.

Cleaned up the OEM fuse box, it will stay for now. Tach is not working, will have to do some troubleshooting on that once the bike is on the rd.

 

The color and paint/stripe scheme is actually attractive for a non-stock, custom job.....

 

Timbox…..congrats!

I’ll send you a private message later on to get info so I can get it on the registry. The nearest number to yours, is #1486.

BTW, it’s ‘emulsion’ not emulation

 

@hogfiddles, yes being left-handed and dyslexic has its perks. I seem to get may words and numbers messed up. Thanks for keeping me on track.

 

Temps are nice and warm this week for the tank to get cleaned. I have noticed that my RPM gauge is not working, I think the only thing that is not working on the bike at the moment. Will have to start to clean contacts and trace out some wires. I took some time between rides yesterday to get the little steam cleaner out. It works good for places you really can't get a rag into. Not too much water left behind and it kinda blasts the dirt and oil away from the area you are working on.

Get out and ride today folks, great start to the day.

 

Tank is done. Looks good but will still add a in-line filter on the fuel line. Did a little plastic welding. Some of the tabs were gone on the rear cowl, is not perfect looking but will hold the cowl down now and no vibration. Still waiting on parts to finish up the bike for a shakedown ride.

 

Got the bike on the rd today. Shakedown was good, bike feels good then I notice no oil light! I am guessing the sending line or unit in the bottom of the oil pan is the culprit. From the pic below you can see I pulled the dash guage off and did check the oil light, it is fine and working as it should be.

oil by Tim Brown, on Flickr
This bike has a 4 into 1 so that pipe is really close to the sensor and the wire.

Fuel gauge is not working, well kind of. On the side stand before I went for the ride, that tank was at half full. But normal operating level up and down of bike, below E. I might have the lines reversed but not sure. They were really brittle and had to do a little splicing. The insulation was very hard and would just snap, no flex. Remember this is just to get everything working and then I will make it look nice after wards.
Gauge by Tim Brown, on Flickr

And then finally the tach is not working at all. I removed the cowl and started to removing, clean and grease all the connectors I could find. I will have to race out the wires and see what is up with them. Must come off one of the coils but not too sure. Maybe one of the other XJ900 folks will clue me in.
Tach by Tim Brown, on Flickr

 

Wire to the oil level sensor was shorting on my bike when l got it. It could be just needing cleaned might be sludged up.

 

@Franz, thanks for the info, will get to it after coffee. You were up very early this Friday. lol

I am guessing the oil sending wire needs help for sure. Under the shifter is just full of oil and dirt (see pic above). I am sure I have oil pressure or the bike would be having issue already. I might have to replace the wires from the fuel sending unit to the connector all together. The insulation on those wires is shot and there were multiple breaks along the short length protruding from the tank tail.

 

Yes better replacing the wires l think.

 

Oil sending ckt up to the wire going to the sensor is good. Grounded the connector and oil light came on. Will have to take the header off to check the oil pressure sending unit. Shorted the wires from the harness side of the fuel gauge, started to climb. Hoping that the sending unit in the tank will start to work right with some riding.

The tach, all wires are good and power and ground are at the back of the gauge. From the TCI to the gray wire on the tach, good. Brown wire has 12VDC and the black wire has a good ground. Also hope this will start to work with a little time.

Going to do a few more loops around the area and see if anything else shows up. Looks like I might have a oil leak on the right side cover or the shifting shaft as it comes out of the motor.

 

I worked on a XJ900 tach for another member and the issue was internal. I am not sure what type of glass circuit card they used but a couple of connections had broken loose. And, you can easily make the etch disappear if you try reflowing the component lead at the feedthrough to get a good connection - so if you get there caution is the word when soldering.

 

@Rooster53 that makes sense and seems to be what is happening here. I will have to tear into that gauge, I guess. At least it is not that hard to get to and work on.

Another 8 mile loop. The fuel gauge is working but is out of spec. Have to have the tank on the side stand to get a half full reading. The trip works on the speedo, so will have to go with that for now.

Head bearing need attention and some small other things. The bike does run well without the rev indicator, I am not too sure how far to push it. I know it has a limiter on it, but still.

 

There’s no rev limiter, unless someone added some aftermarket part. The 900rk “rev limiter” is a combination of EYES, hands, and feet.

 

Got motivated this afternoon and thought why not throw it back on the table. Took the header off removed the oil sending unit.
oil swx by Tim Brown, on Flickr
It was frozen up. Sprayed some B12 and hit it with air a few times. Now you can hear it rattle when you shake it. Tested on the bench, good to go. Painted the headers and let them dry a bit, put the the bike somewhat back together. Put the gauges on lose and fired her up. Oil light came on and went off. Wonderful, small steps in the right direction.

Now those gauges. Going to have to take my time wit these and look for broken wires and or cold solder joints. I have not taken the board out of the gauges yet, a little hesitant on that.
tach 11 by Tim Brown, on Flickr

 

Removed the tach, didn't see any cold or broken solder joints. Did a little bit of testing on the board but could not find anything. I am guessing one of the components on the board, resister, cap or other failed. So for now it is what it is. Will ride it for a while and keep my eye out for some gauges. lol

 

If you still have it apart and have an older VOM you can probe the red / black wires to see if the meter movement is working - those old meters put out close to 1.5V at Rx1 and Rx10 with a low impedance.

 

Those are easy to pull off and take apart, I will try to see if I can get it to move. I did check all contacts for continuity with the meter, no loose or broken wires.

 

BTW, there is an over-rev limiting function on the bike, it's the yellow/black tracer stripe wire from the TCI that goes into the cluster. Here's a good write-up about it, although it was written for the XZ550 models, it should apply to the XJ900 models too:

6.1
The VISION has a "REV-LIMITER" circuit that kills the FRONT coil ignition if the TACH reads over 12,000rpm. The TACH reads the fire pulse from the TCI to the REAR coil. If the circuit malfunctions you'll most likely lose the FRONT CYLINDER ONLY.


6.2
DISCONNECTING REV LIMITER
*** CUT YELLOW/BLACK striped WIRE in 6-prong plug at TCI!! *** (Tape the ends)


6.3
HOW TACH & REV LIMITER WORK

The Tach has 4 wires connected to it:
[BROWN] = +12 volt Power
[BLACK] = -12 volts Ground
[GRAY] =
Ignition pulse signal that the tach reads. It is a splice "tap" off the Gray wire from the TCI to the REAR cylinder coil.

** That's why if you lose the rear cylinder ignition you lose the TACH. **

The GRAY wire signal from the TCI is a "square wave" trigger to the Coils primary winding. It is normally "near" ground and the trigger is +12v to fire the coil and pulse the tach. To be exact: in the Tach I dismantled the GRAY wire became ORANGE after the 3-prong connector block outside the instrument cluster (contrary to every wiring diagram I have).

YELLOW/BLACK stripped wire = this is the Rev-Limit connection. This is a single wire between the Tach and TCI. When the "Rev-Limiter" switches ON (IN THE TACH) it grounds the YELLOW/BLACK wire. You can try this yourself. At the TCI disconnect the YELLOW/BLACK wire in the 6-prong plug in the side of the TCI. Then while the bike is running, ground the pin where the YELLOW/BLACK wire would be connected. It causes the same thing:

The "Rev-Limiter" KILLS THE IGNITION to the FRONT CYLINDER coil.

If you're curious how I know this... I connected an "oscillator" to the Tach, powered it up and ran the tach up to... well, pegged it. It thinks it's connected to the engine. At 12,000 exact it grounds the Y/B wire.


6.4
[INSIDE THE TACH]

Inside the Tach are 2 small separate circuit boards. One is the Tach. And the other is obviously this "Rev-Limit" switch. I say "switch", but this is a "solid-state" switch (NOT a mechanical one). An IC chip on this board is obviously counting RPM. Now WHY Yamaha put the rev limiter in the Tach?

I have no idea. In most systems its INTERNAL to the TCI since it is already doing "THE MATH" in the timing chip. But this was early generation stuff and maybe they couldn't pull that info "OUT" of the timing chip. So instead of adding ANOTHER rpm counting circuit to the TCI they just used the one they had to put in the Tach anyway.

 

Interesting about the Tach. I will take mine apart again and get some pics of it. @Rooster53 thinks mine is the old one. There was only one small ckt board with red and black wires running to the RPM base fed from the ckt board. The board was also glued in place and I didn't want to disturb it too much. Even though it is not moving the RPM needle, it could still be working as another function as @chacal mentioned. Have rain here so might as well work on some bikes.

 

There is the guts of the Tach
5wo2LRKW by Tim Brown, on Flickr
CKiJ8h73 by Tim Brown, on Flickr
-ajRSglF by Tim Brown, on Flickr
Good steady rain here, so good time to work on some bikes.

 

Caps look good.

 

I did a little test but not to sure if it shows it broken or not. I have a tone generator in the 1K range, but I think that the bike is 5k and above when it is running. I hooked power and ground to it with jumper wires and then put the tone generator on the ground and the gray signal wire hoping the needle would move, nothing. Had to try something while I had it back out. Ebay will have to be my saving grace to get a good working cluster. Part of the fun of getting these older bikes back on the rd.

 

That 1K is a bit high - you can do the math 1000 cycles per second X 60 = 60,000 per min - you need something in the 60Hz range, like AC power but that gets a bit dangerous.

Look very closely at those solder joints and give a gentle wiggle to the components to make sure they are secure. That is a glass board with internal laser trimmed resistors and it does not tolerate soldering - that was my experience with it anyway and it required fine gauge jumpers to repair

You can also connect a 1.5V battery to the red / black wire to test the meter movement - observe polarity and keep plus on red. The meter movement is somewhere in the neighborhood of 200 to 300mv /1000rpm, so the 1.5V should move it up to about 5 - 7K RPM.

 

1.5V test worked, deflected about 5.2K RPM. Thanks for the test @Rooster53 . I still have no idea about fixing it....just going to replace it.

Took the rivets out of the windshield. Cleaned under the shield and fixed some issues. Put the shield back on but not to sure yet if it will make noise or stay on at speeds. Might have to get some different fasteners to make it better secured to the cowl.

 

Pop rivets?

 

Yeah, that was going to be my question, too..........

 

Yes, the PO had put pop rivets in the holes of the windscreen with washer on the back side. I will end up getting some SS screws with nylon nuts to replace them.

 

Good old PO's, where would be without them?