no spark... still

Port

Port

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I'm not getting spark on my 1981 XS650 heritage special. I replaced the wiring harness and plug boots. cleaned almost all of the connections coming from components to the harness and cleaned the kill switch and ignition switch contact points. The coil tests good but the case has some cracks in it, I'm thinking I'm going to replace it but I haven't decided for sure yet. The harness came with glass fuses that i'm going to replace at some point but, seeing as how they are brand new and aren't causing voltage drops across the fuses I don't see theme as a probe at the moment. That leaves me with the TCI box as the problem, as far as i can tell.

Pictures of TCI Unit: http://imgur.com/a/FM784

I think I may have found the culprit but I'm not positive. Note the red-ish colored component next to the 2 resistors. It looks like it has suffered some damage from overheating. I'm not sure what the component is, how to find out what it is, or how to test it to see if it is indeed fried.

I've also read that the 4 diodes just past those same 2 resistors are known to be troublesome. I've read some places that you can test them in place and have also read that you can not test them in place. If i can test them, how do i do so?

The solder points look pretty good for circuit board that has been strapped the the bottom of a bike for 33 years.

Lastly, i haven't been able to figure out how the handlebar controls are grounded to clean the contact points or how to check them for ground.

Any advice is welcome
 
They used two methods to ground the bars.
Early used a wire from under the nut on one of the bar risers to one of the upper tree clamp bolts.
This had a ground path of Switch housings to bars, bars to risers, risers through the wire to upper tree, to the fork tubes and steering stem to the bearings, through the bearings to the frame, Not the best ground path but it works, The only time the ground is used is for the starter button and the horn button. Neither get used much.
Later the ground path was from the switch housings to the bars, on the left switch housing was a black wire that runs down into the headlight bucket and plugs into the harness ground. Harness ground hooks to several places on the frame which is where the battery ground cable is bolted to.
This bypassed the neck bearings, this is a good thing. The electrical current flowing through the bearings causing excessive pitting. to the balls and races.
To check for a good ground path use your ohm meter on the lowest scale. Touch one probe to the battery negative post, the other to the bars or switch housings. You should get a very low reading.
With my meter I get .1 ohms touching the probes together. This is the ohms of just the leads. When I touch one probe to my battery negative post and one to the bars I get a .2 ohm reading. So .2 - .1 = .1 ohms for the ground path.
Your may be higher or lower. Even at an ohm I might not worry to much. Things will still function. Lower is better. If very high just clean all connections along the ground path. Housings to bars, early bars to risers, risers to wire, wire to clamp bolt, to trees ext. you get the idea. If you bike does have the ground wire from under the riser nut I might suggest unhooking it from the tree clamp bolt and extending it so you can plug it in the harness ground in the headlight or under the tank to a coil mount bolt.
I think the coil mount is the better option, It will be easier than building an adapter to plug in the harness ground. They used every ground connection some where. No extra's. You would have to build a Y adapter that you could unplug a ground, plug in the adapter then plug the old ground and new ground into it.
Leo
 
I was going to add in my last post that the handle bar ground has nothing to do with the spark. The engine stop(kill) switch is just that a switch. Power comes to this switch on a red/white or brown wire, different years used different colors, Out on a red/white wire. It does not ground anything. Just turns the power on/off.
I'll look at your pics, my dial up loads slowly, and get back to you
Leo
 
You can try to test them in place but you might get false readings. Those components hook to others and can have a connection to the other end of the item you want to test.
Unsolder and lift one end of the diodes up out of the board. A diode is a one way valve. In testing you set your ohm meter to medium scale. Like 2k. Touch the probes to each end of the diode. No switch probes. One way you should get a high resistance, the other way a low resistance.
You may have to try lower scales for the low side and higher scales for the high side. If you get at least ten time as much resistance one way as the other they are probably ok.
The dark color you see on the wire from the diode down into the board is probably from the rosin core of the solder used to solder it to the board. They may have gotten thing a bit warm on the install. Or a PO over heated it. I have fixed TCI boards by just resoldering all the joints on the board. Just heat till the old solder melts, sometimes a touch of new solder helps.
There are TCI board repair threads on here somewhere. They talk about replacing parts.
You can try fixing what you have but I might just replace it all with a Pamco. On the TCI bikes I think I would use one with the E-advancer. Simpler install, no mechanical advancer to mess with.
I have run both on my 75, they mechanical advancer works fine but it can take some tinkering to get just right. The e-advancer, no fiddling, just install, set and be happy.
It runs just a touch smoother than the Mechanical unit, no slop in parts to cause excessive play in the timing.
Leo
 
A picture of the coil would help in determining if it needed to be replaced. Also was your rotor every changed or replaced? I to have an 81 that was causing me all kinds of fits, very weak spark, would start and idle ok, but rev it and it went all stupid on me, backfiring, popping, just flat out would not rev up. I just found all of this out myself so a quick test is to unplug your reg/rec and start the bike. Does it start and rev with the reg/rec unplugged? If so then check this thread out. It fixed my issues, and took all of 3 bucks and 24hrs of waiting to allow the JBweld to cure. http://www.xs650.com/forum/showthread.php?t=36526, just something to think about before blaming the TCI. The weak or no spark symptoms can mask themselves as TCI problems when in fact that little tiny ass magnet embedded in the rotor could be the issue. Many thanks again to everyone who pointed me in that direction.
 
Thanks everyone! I don't have any questions at the moment but, I'll get back to y'all tomorrow with what I do/find
 
I felt stupid, but recently I spent a few days chasing a very weak/no spark only to find what I should have checked first; fouled spark plugs, even cleaning with a brush and spraying off with contact cleaner didn't help. Popped in some Iradium plugs and she fired right up.
 
I have similar problem with my 1983 HS. Bike was running fine then stopped dead in the middle of the road. Coil seemed bad and I put in a Green Monster to no avail. Got a spare TCI and that didn't do it. Do kill switches ever fail?
Getting funny readings from the 6 way plug to the TCI. The red and orange wires show voltage when grounded to the engine or battery but not to the 2 black wires in the plug. The black wires show voltage when grounded to the neg terminal of the battery. That seems not right.
 
hi there im very new to the xs650 world...and this forum so 1st things 1st hi everyone.
right i have a 1979 with no spark at the moment im working my way through the possibles ...just tested my coils and the saying 4.1 on primary and 14000 on the secondary does this sound ok . any help with this will be appreciated .p.s sorry to jump in on post but thought it was a similar problem cheers
 
wakman, yes engine stop switches can fail. good thing is they are easy to fix. The switch can be removed from the housing and cleaned.
docking, That sounds ok for the coils. There are other things to check too. A quick run down on how the points system works. Power is sent from the battery to the main switch, then to the engine stop switch, from the engine stop switch to the coils. From the coils to the points and condensers.
How as the engine turns the cam lobe on the advance rod opens as closes the points.
The points gap and position effect the spark and timing. If the points gap isn't right they won't open and close right. This can cause weak or no spark.
First thing you need to do is inspect the points, Are they clean. No burning or pitting can be seen? If they look good check the gap. The "how to" is in your repair manual.
Once properly gapped time them, in the book too.
Now you should get spark, if not test for voltage at the red/white wire the coils plug into. With the key on check the battery, then check the red/white wire, they should be the same, or within about .2 or .3 volts.
If the voltage is not up to battery voltage, your key switch, fuse holder, engine stop switch or any other connection between the battery and coil is suspect.
The key switch and "kill" switch can be removed, torn apart and cleaned.
Leo
 
Port said:
I'm not getting spark on my 1981 XS650 heritage special.

I've also read that the 4 diodes just past those same 2 resistors are known to be troublesome. I've read some places that you can test them in place and have also read that you can not test them in place. If i can test them, how do i do so?

The solder points look pretty good for circuit board that has been strapped the the bottom of a bike for 33 years.



Any advice is welcome
Click to expand...
looking at the image of your TCi pcb board looks like you have at least one blown capacitor there, possibly more. They are quite clearly bulging from the top.
Easy enough to get some replacements from RS and solder them in.

The 4x diodes you refer to are rectifying diodes arranged in a bridge configuration that convert your AC to DC voltage in-circuit, switch your multimeter to 'Diode' mode and place the black negative lead on the striped end of each diode and the red positive lead on the other end. You should see a reading of between 0.4 and 0.6 for a good diode .
 
Last edited:
Today I found a thread about checking and replacing the transistor. The one on the TCi failed the test and so i bought another and replaced it on the board but it again failed. I removed the new one and tested it again and it passed, like it had before installing it. So, something else is wrong with the TCI but i'm not pretty confident that TCI is the cause of no spark. Tomorrow I'm going to resolder all of the connections and see what happens, I may end up replacing a few other components.

Peanut: It does look like it's bulging in the picture but I don't think it is. The capacitor is very small and the picture, being so close up, distorted the prospective.

Leo: I'm going to test the diodes and handlebar tomorrow and i'll get back to ya
 
Perhaps I just didn't see it but have you checked the strength of the magnet on the rotor and ohmed out the pick ups? the pickups should show about 650 ohms orange or grey to black, one magnet test is to unplug the voltage regulator then crank. Are you working from a known good fully charged battery with good ground strap? Have you measured 12 volts at the coil?
 
gggGary said:
Perhaps I just didn't see it but have you checked the strength of the magnet on the rotor and ohmed out the pick ups? the pickups should show about 650 ohms orange or grey to black, one magnet test is to unplug the voltage regulator then crank. Are you working from a known good fully charged battery with good ground strap? Have you measured 12 volts at the coil?
Click to expand...

I've not messed with the rotor nor pick ups at all.

Whats the best way to check the pick ups and what do they do? I've seen that you pass a magnet across it as you are testing the resistance but I feel like there might be a better way.

I replaced the battery recently as it was worn out.

I already tried it with the rectifier-regulator unplugged, no luck.

I'm not getting full voltage at the coil but I can't figure out why. here's my post about that http://www.xs650.com/forum/showthread.php?t=35537

I've never actually tested the ground strap but i will later today.





Peanut: I'm going to do just that later today, replace those 4 diodes as well as the Zener i mentioned looked burned.
 
The Pick up is a pair of wininings in a single case. As the magnet in the rotor passes the pick ups, a small current is created in each winding. This current goes to the TCI box.
The TCI box uses this current as signals to tell the engine position and rpms. It uses these signals to tell when to spark and how much to advance the timing.
The only test I know of is as described in the repair manual. As on page #181 in the Clymer's book.
If they ohm out ok then they are good, if not they can't create the current that the TCI box uses as signals.
Page 182 has a trouble shooting guide to determine why you have weak or no spark.
About not getting full voltage at the coil/TCI box I talked about that in post #14. The key switch, engine stop switch, fuse holders. All need to be clean.
The stock round glass fuses where all they had back then, even new they were crap. As they are used their is resistance to electrical flow, this causes heat, this heat weakens the clips that hold the fuse. This weakening of the clips increases the resistance, creating more heat. This progresses to a point that the clips break.
Best to replace the stock fuse box with the new style blade fuses, either inline fuse holders or a new fuse block.
This may be why you have no spark, low voltage. If the fuses box is bad nothing you do will help till you fix the low voltage.
Leo
 

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