82 running on 2 cyl

[ej313]

Ok I need help, my 82 is only running on two clyenders (1&2) the other two have weak sparks and cut out at 3500 RPM. spark units check out fine, coil checks fine, can not find problem.

 

[joedrum]

plug wires and caps probably resistors in the caps maybe

 

[ej313]

No they check out @ 5k ohms

 

[slabghost]

Check coil mounts are clean and tight as this the ground. Check your coil power supply has the same voltage as the battery. On most wings that would be black wire with white stripe. Check you spark plug gaps are not beyond .028 .Check your battery and ground connections are clean and tight. Might want to clean the kill switch also. Let us know what you find.

 

[joedrum]

the coils are old and could be weak on that side ....there good for checking out good and failing in use..... :mrgreen:

 

[dan filipi]

Knowing the history of this bike would help.

I would take a good look at those plug caps but first try swapping the coil primary wire.
Since 1&2, 3&4 share coils, by swapping the primary you'll know if it's the coil/wiring or plug wires.

Back to the plug caps,
they are screwed on to the wire and tend to corrode over time where the little pin contacts the center conductor in the plug wire. They can be unscrewed then cut a 1/4 inch of wire off but also make sure the pin is clean.

The resistor is to reduce radio static but it's possible to use resistor plugs in place of them in which case the resistor should be removed. If it's left in place then you get double resistance at the business end of the spark plug which could reduce spark, which is not real hot on these bikes to start with.
If you remove the resistor a solid piece of #8 copper wire fits in place nicely.

 

[ej313]

Thanks to every one who responded, but let me bring everyone up to speed. Starting at the plug caps, I took them out of the circuit and tested with a 5K ohm reading on each. The circuit in question (3&4) cly has a new coil (now I know I could get a defective part, but the current coil is doin the same as the old coil) to top that off, I swopped coils and the problem does not follow. Leading me to belive the coil is good. As to voltage @ the coil (input) it is the same on both coils. On up the line @ the spark unit, again with all things being equal, I swapped them with out with the problem not changing (still at 3&4) so spark unit good. Again I also followed the test procedures in manuel and found no ill results. I did the grounding of the pulse gen lead test with good results. Ohm tested the pulse gen with a reading of 570 ohms @ 80 degrees (spec is 530 +/- 50 ohms At 68 degrees). Here is another thing that troubles me, I connected a spark tester to the spark plugs, 1&2 fire great, 3&4 is a noticable weaker spark. Plus when engine is reved to 3K rpm, spark gets weaker and at 3500 rpm, spark goes away compleatly for both 3&4 cyl. Am I looking at pulse gen issue? Again thanks to everyone for your help

 

[joedrum]

im not sure you can but if you could cangege the connection at the pluse generator you could check that like the coils and spark units ...im thinking its a one way connector there first connection from the rear pluse generator they dont go bad often but do ...this might be the first one here on this forum maybe ....from everything you said it looking that way .....two different coils wires and all good even spark unit checked in switching test....not much left but pluse generator moduals

 

[ej313]

I've looked at that connector, looks good and clean. I did a voltage check at that connector (not in the book) but both pulse gens read .8 vdc. Again I do not know what if any voltage reading should be at this connector, but they were both the same. Between the voltage and resistance for pulse gen, I am confused.

 

[joedrum]

me too on what it all means as in checking.....is there a way of switching the hook up over to see if this moves the problem to the other side

 

[slabghost]

To me it sounds much like a coil going bad. but you say swapping coils makes no difference. You may want to try this modification to get full power to ignition.

 

[dan filipi]

The 4 pin plug does go bad, I had one of the wites break off and replaced it with a 4 pin trailer plug both mail and female ends.

As a test for pulsers the 2 pairs can be swapped.
Color code is in the wiring diagram.
I don't think there is +12 volts on those pairs rather its a ground signal.

 

[ej313]

These are great ideas, thanks for everyone's help. I have to go teach a motorcycle safety class, but as soon as I get home I am going to try these ideas

 

[joedrum]

yes i think if you can switch the pluse generator wire to see if the moves the problem if it dose its the modual thats bad if not your chasing some kind of bad connection or broken wire or something

and maybe the rewire slabgoust was talking about is the right move if its a wiring issue

 

[dan filipi]

Here's the gallery page for the wiring diagram gallery/image_page.php?album_id=232&image_id=3571

And here's a little snippit of just that area.

 

[ej313]

Ok I did the test w/unpowered test light, ground is good, but if I connect test light to ground and touch the blue connector on the left coil (#3&4) while running the bike stutters a little. If I touch the yellow connector on the right coil (#1&2) there is NO stutter but in both cases the test light illuminates. Also if I touch the common on both, the light illuminates w/out any stutter. Now when I connect the test light to ground (engine running) and probe at the pulse gen connector, for the lead for #3&4, there is a slight stutter, but will continue to run (1&2 working well). Then probe lead for 1&2, will stumble hard and if not removed quickly will kill the bike (3&4 not working well). Here is my train of thought, there is a ground inside the pulse gen for #3&4, this prevents that coil from fully charging hense the weak spark and as the engine speeds up, prevents the coil from charging at all hence the spark just goes away all together. Thoughts anyone?

 

[ej313]

Ok Im doubting my latest thought. If I have a ground in the pulse gen as I think I do, then why are my resistance readings good? 580ohms for both pulse gens. No shorts to ground.

 

[ej313]

Alright, another reading with engine running; ohm reading @ pulse gen connector, 3&4 = 13M ohm, 1&2 = 15M ohm. Has anyone heard of or used these readings or what they may signify? Remember engine running

 

[dan filipi]

Your tests of the pulsers say they're good so id swap the pulser leads to confirm.
If the problem moves then you know.

 

[ej313]

How do I swap with such a small / tight connector. Plus will that also throw the whole firing order out of wack?