Uh oh, losing power above 5K

I have a carb shop so I don't have all that many electrical diagnostic tools but almost any decent bike shop will have a coil tester. If you recall, when I originally made some suggestions, one of them was to spray the head pipes after a hard run where the bike performed badly over 5K rpm. If you spray the pipes, you will get a sense if the cylinders are firing. Water will roll off pipes where the cylinders are not firing. It will vaporize where the cylinders are firing. If you find cylinders NOT firing, then you can make some decisions on what steps to take or where to go with your diagnostic attempts. For instance, if one pipe is cold, this tells me something (ignition OK but possible bad plug or plug wire or valve issue or carb issue). Two pipes cold where the pipes are 1 and 3 cold, then I would look at basically the same things... two pipes cold say 2 & 3 (or 1 & 4), then I would start looking at the ignition or coils or associated wiring.

At some point, you should start doing some pointed troubleshooting where your efforts will point to the actual problem.

How did you measure resistance on the coil wires? To measure primary resistance, put your probes on the lugs where the small wires are connected in Ohms scale (lowest). Measure secondary resistance (you have TWO sets of windings and the secondary can be shorted) on the contacts for the the spark plugs or if you can remove the wires, on the contacts where the wires connect to the coil. Put the meter in Ohms scale on a much higher scale since you will be looking at 10-20K Ohms.

Both the 2&3 pipes are cold, 1 and 4 are firing. I could touch them upon initial start up and it was clear

i measured resistance as the book stated. i took out my multimeter and measured ohms. I removed the coils and put the leads for the secondar resistance on the side that connects to the spark plug wires. I forget the exact number, but it measured within spec and both coils were equal.

For primary resistance I put the leads onto where the wires from the harness connect to the back of the coil and i got a reading of 3.0 ohms on each. However while the wires from the harness were connected to the coil, I recieved a reading of 3.0 on one, and only .8 on another. I do not know what significance that plays

I traced to the points to see if they were in spec, and one set of them had damage. On side of the contact was missing some metal, while it appeared that missing metal had melted to the other side, so i replaced them.

the coils tested out okay so i have eliminated that as the problem. I also have brand new plug wires and plugs.

i do not know how to proceed or what to test next. I am doing troubleshooting to find the problem, and it has been logical, but I cannot find the source of the problem

have you checked the voltage to the coils, also look at the plug wires

the wires are brand new. how do i check voltage at the coil? Put the multimeter leads up to the wiring that goes into the coils and turn over the motor?

Also I checked spark across all 4 plugs just now and only 2 and 3 have spark. The bike is no longer running or starting. I have no idea whats going on.

freebyrd24 wrote:

Both the 2&3 pipes are cold, 1 and 4 are firing. I could touch them upon initial start up and it was clear

i measured resistance as the book stated. i took out my multimeter and measured ohms. I removed the coils and put the leads for the secondar resistance on the side that connects to the spark plug wires. I forget the exact number, but it measured within spec and both coils were equal.

For primary resistance I put the leads onto where the wires from the harness connect to the back of the coil and i got a reading of 3.0 ohms on each. However while the wires from the harness were connected to the coil, I recieved a reading of 3.0 on one, and only .8 on another. I do not know what significance that plays

I traced to the points to see if they were in spec, and one set of them had damage. On side of the contact was missing some metal, while it appeared that missing metal had melted to the other side, so i replaced them.

the coils tested out okay so i have eliminated that as the problem.

Unless you have a tester which can fire them under load, you can't test them. Coils are high voltage transformers and the secondary windings have to be able to handle at least 60 KV in modern applications. The insulation on the windings will break down over time and show up when running, but not always with an Ohm meter.

The condition of the points you describe indicates that the coil may have been bad and causing an excessive voltage to appear at the points. There could be another problem, but based on your description, that sounds like coil damage.

You said above:

the bike has has new points, new condenser, new plugs, new wires and its running off of cylinders 1 and 4 only. I switched the coils to see if it was a coil, and it did the same thing, so not a coil problem

Clearly, something took out the points. Try installing a good set of points and running it. Then, try swapping the coil and see if the two "dead" cylinders start running with the coil from the "good" cylinders.

sorry i didn't word it that well. since i only had cylinders 1 and 4 firing, i switched coils to see if the good coil that just worked would work for the 2+3 cylinder, and it did not

The one that originally did not fire 2+3 then fired # 1+4. i mean could it still be a coil issue?

I don't know anything other than a coil that can burn up a set of points like you describe.

Does your bike have one set of points or two?

leaving the key on without rolling the engine can burn up a set of points if they are closed. Try switching the wires on the condensors. That would be an easy fix for you!

i have two sets of points. one on the left side, one on the side side, condenser underneath it

what would switching wires on the condenser do?

If not already done, would test continuity of wire feeding positive battery voltage to coil (after disconnecting it from the dual socket which feeds both coils).

While the outside appearance of the wire may look perfectly okay, the inside wire might be frayed or broken underneath the insulation. May use an ohmmeter to do this test, which is basically to assure integrity of the inside wire.

While doing the test, manipulate the wire and wiggle it all around to see if the ohmmeter jumps, which would indicate an intermittant connection. And which could result in intermittent power to the coil primary winding.

Good Luck!

A defective or shorted condenser (aka capacitor) will cause the points to arc and burn. Any arcing should be visible while motor is running or while attempting to crank by spinning it over with the starter. But the new points and condensers should have resolved any problems with those components.

The windings are inside the coil and thus, primary resistance should be measured on the lugs that retain the red/yellow and green (or black) wires. If you measure the resistance through the wires, you are introducing the very real possibility of error. You have an electrical issue in the ignition system. See that you have swapped coils and the problem stayed on the 2 & 3 cylinders (if I understand what you said)... ok the problem may not be in the coils but in the points or condensor. It could also be in the wiring between the right hand points/condensor and coil. Check to see if the green wire has good contact all the way back to the points/condensor. If it does, I would remove and replace both sets of points/condensors and replace them with a Dyna S ignition. If this isn't possible, replace both sets of points/condensors. Gap the points.