Topic: 73 cb500 backfires and wont start..

[75 honda]

My bike will turn over but just keeps turning over with an occasional backfire out the exhaust.

[LesterPiglet]

When was it last run and what did it run like then?

[75 honda]

rode great a couple weeks ago. Then it wouldnt shift into gear so I split the cases and put new forks in. Put it all back together and now it just turns over and backfires. I thought maybe I had the cam 180 out or something so I went back in and adjusted it. TDC on the #1 with the T mark lined up and the notch on the cam facing forward. I also messed wit the tappets adjusting them some. I screwed up something somewhere..

[TwoTired]

Very coil to plug wires 1.4 coil, 2.3 coil, and that the proper point set is connected to the correct coil.

Did you take the spark advance mechanism apart?

[75 honda]

I did take it apart.

[TwoTired]

I did take it apart.

If it was assembled 180 degrees out the timing will be out, too.  Swap yellow and blue, if it goes back to life, then fix the advancer assembly.

And slap your wrist, for not marking things properly for reassembly.     /jk

[75 honda]

Okay so I switched the yellow and blue and got a lot more response and no backfire. Didn't fire up though, battery started to die. So what do I need to do to the advancer assembly?

[75 honda]

I played with the advance plate a little and I got it to start. Ran like #$%* and I had to keep the throttle pulled to keep it running. I noticed the points and condenser isn't spark all the time. Its hit or miss.

So blue and yellow wires are backwards, whats the fix for that?

Next Ill try getting everything in time and possible new points and plugs, I noticed they were black.

Anymore help or ideas would be great.

[TwoTired]

So blue and yellow wires are backwards, whats the fix for that?

Reassemble the spark advancer correctly.

[CB750F2]

Read through topic 110623 for an explanation on how to assemble the advancer correctly. Pat

[75 honda]

Kinda of new to the site.. How do you look up topics?

[75 honda]

So I looked it up and it's pretty simple looks like. I did what it said to do which is just line up the pin with the hole and then slide the plate back on and the bolt. If I was 180 out would it cause the wires to be crossed?

[75 honda]

Okay forget about all this 180 out. My wires were crossed so I went back up to the coils and switched them and then went back to the points and put the correct color to the matching color. Its running but now I'm trying to set the time with a dwell meter and timing light. Not going so well.

[TwoTired]

The dwell adjustment is the same a setting the point gap.
  Just set the gap while the points are on the highest place on the point cam.
The point plates are then rotated to achieve the correct timing.  When the three screws are loosened the plate can move rotationally, as well as radially.  This is far more of an issue during strobe light timing than static timing with some point plates as teh point cam and point springs tend to make the main plate "wander".  There is a FAQ entry for dealing with this.