Ebay special 81 xs

[bultaco59]

Hello out there in xs land, well heres the deal,I bought this bike on ebay for 600
I got yesterday, through a batt in it, starter didnt work, got it working ,next check for spark, no spark, due to this bike being completely unmolested,not a wire out of place
im thinking (hoping) that it will be something simple,what is the most common cause for no spark, im a cb guy and a points guy,this tci system makes my skin crawl.Im sure its
fine just not used to it yet. any ideas ??

Please and thank you
Bob in burbank

 

[angus67]

get a manual. ohm the coil. A couple pairs of autolite ap 63's Gap to .035.
sounds like you've worked on older bikes before, so you know the drill. stiff wires, corroded connectors. The 80 and up bikes are chocked full of "safety" features, but one you get past those, these bikes are quite easy.

 

[scabber]

It could be the TCI igniter is bad. A picture of the bike would show us what your working on.

 

[bultaco59]

Hello again, well so for this is what I have found, if you guys could tell me what you think, these are base reading, so once I go through all the wiring I can see if its better or worse.
Battery starting voltage 12.74 v

Coil: voltage @ r/w wire 12.10 v
primary 2.5 k ohms
secondary 12.35 k ohms
plug caps 10.0 k ohms
I think these are the wrong caps.

Pick up: bk to org 783 ohms
bk to gray 794 ohms

TCI : voltage at r/w wire 12.12 v

its starting to look like the TCI ???

any thoughts.
please and thank you
bob in burbank

 

[retiredgentleman]

Hello again, well so for this is what I have found, if you guys could tell me what you think, these are base reading, so once I go through all the wiring I can see if its better or worse.
Battery starting voltage 12.74 v

Coil: voltage @ r/w wire 12.10 v
primary 2.5 ohms
secondary 12.35 ohms
plug caps 10.0 ohms

Pick up: bk to org 783 ohms
bk to gray 794 ohms

TCI : voltage at r/w wire 12.12 v

its starting to look like the TCI ???

any thoughts.
please and thank you
bob in burbank

If you actually mean secondary is 12.35 K ohms, that would be about right.
12.35 ohms would be very bad.

Plug caps are supposed to read about 5 K ohms each. 10 ohms ?????

 

[bultaco59]

That is what I mean, long day, just add a k to all the ohms readings.

 

[retiredgentleman]

Well OK, with the revised numbers you have given, it does point to the TCI black box as the leading suspect. 34 years is a long time for any ignition to survive.

You could remove it from the bike and have a look inside. Some lads have even found water inside the box.

There is no way to test the black box other than direct substitution with another, known working, black box.

Did the E-bay guy mention anything about no spark?

 

[XSLeo]

It may be the voltages. With that much drop from battery to TCI and Coil the connections between them could be the issue.
The key switch is one problem area, it can be torn down and cleaned. The engine stop switch is another. It to can be torn down and cleaned.
Your fuse block can cause issues. When new those round glass fuses and the clips were crap, thirty years of use haven't improved them. Replace with modern blade type fuses.
On any wiring connectors you can pull them apart to clean and tighten them too.
A bit of dielectric grease will help keep things clean and corrosion free.
On my 81 it ran pretty crappy till I fixed the voltage problem. It also had charging issues so it took a bit longer to get right.
Being a new to you bike I would also recommend starting at one end of the bike and work top the other going through the entire wiring taking apart, cleaning and tightening every connection. It's time consuming but helps fix a multitude of electrical issues before you find them.
Leo

 

[bultaco59]

Good Morning, I took your advice,cleaned every connection,ignition contacts, kill switch
contacts with wire brush,contact cleaner,diotec grease.pulled tci took a look it looks
brand new, I still only have 12 v at tci and coil, BUT I NOW HAVE SPARK, it wouldnt spark unless I grounded both plugs at the same time to test one,is this normal ??the spark is weak,but it a spark
I now have to install a blade fuse block Im hoping this will raise the voltage drop.
well I'll keep at any more ideas would work for me. I checked the compression it was
just short of 120 psi, this bike has not run in years( many) my understanding is that
once it runs for a while the rings and valves will seat and the compression will come up
Im hoping,I'll wait for fuse block and see what happens, after that ck timing,adjust
valves,pull carbs, change oil, and give it a go.oh one question I have 10 k plug caps would reduce the spark?? I should install 5 k caps is this correct??


Please and thank you
bob in burbank

 

[angus67]

yes you need 5k caps.
And of course you have to ground the plug to get spark.

 

[bultaco59]

really, no shit !!

 

[angus67]

"BUT I NOW HAVE SPARK, it wouldnt spark unless I grounded both plugs at the same time to test one,is this normal ??the spark is weak,but it a spark"
you asked.

 

[aldo5468]

bultaco, on these TCI-equipped 650's, both plugs need to be grounded if you need to remove one to test for spark, set idle mix, etc. The system is designed to fire both plugs simultaneously every 360 degrees of crank rotation, even though one cylinder is on its exhaust stroke, and can be damaged if both aren't grounded. Pic shows what works for me.

 

[XSLeo]

The path the spark follows is from the coil down one plug wire, into the plug, the spark jumps the gap to the engine block. In this situation it's not ground. Just a conductor.
The spark travels through the engine to the other plug, jumps the gap, up through plug, wire and back to coil.
When checking plugs I use a section of the bare ground wire from a piece of house electrical wire. A piece about 18 to 24 inches is plenty.
Strip out the bare wire. Use a plug and wrap one end around the threaded part of the plug. Do this on both ends of the wire. Use enough wraps to get a good solid connection. Tight enough you have to screw the plugs in/out.
Now just slip this wire in across the top of the engine. Put good plugs in each end of the wire. Plug the plug wires to the plugs.
Test for spark.
This works well. You can see both plugs.
Leo

 

[bultaco59]

Thank you guys for the help, I used a allagator clip test wire, I have spark, sprayed
alittle starter fluid and she fired, by the looks of the carbs this bike hasn't been running
in a VERY long time, twenty years maybe, I have the carbs apart, waiting for parts, so im
going to flush the motor with fresh oil a couple of times, check the valves,(adjust)
then Im going to give it a go see if she will run, I bought pods to put on the carbs
so I ordered 145 mains and 42 pilots and the and the needles with adjustable clips
which clip position would be a good starting point. im hoping the charging system
is working we'll see.
thanks again
bob in burbank