Topic: 2 cylinder not firing

[cr0issqnt]

I just got my bike together and running yesterday but at first only cylinder 2 and 3 were firing and so I cleaned the points and checked the bullet connectors at the coils which fixed it, but now cylinder 2 doesn't fire which leaves me stumped. I checked spark, I saw and felt it so my only guess now is the carburetor to check for fuel. I don't really want to tear the bike apart having just got it back together and knowing that cylinder 2 was just working. Is there anything missing that I am not thinking of?

[Ozzybud]

Check the simple stuff first.  You could have just fouled that plug.

[Don R]

 It has surprised me in the past how good a plug can look and still not fire. You can swap with another one and see if the miss follows it.

[HondaMan]

Are the condensors new, and where did you get them?

[cr0issqnt]

I cleaned up the spark plug with carb cleaner and a toilet brush I use for cleaning more delicate things and I left it overnight to cool down I still don't think it is working. i will let it cool down and try and switch plugs around. The condensers are not new.

[cr0issqnt]

I just switched the plug for cylinders 1 and 2 and still the exhaust from cylinder 2 feels cold

[HondaMan]

Do you have an ohmmeter? If so, check the resistance of the sparkplug caps on the #2 and #3 plugs. They should be within 800 ohms of each other (if they are around 5000 ohms). If they differ by more than about 1500 ohms, then only one plug of the 2 on that coil will usually fire.

If the plug caps are the higher-resistance type (10,000 ohms) then they should not differ more than about 2000 ohms.

[cr0issqnt]

I think I am doing this right but I am not sure how to read it right. I have both probes touching the wires that go into the spark plug caps and this is the reading.

[HondaMan]

I think I am doing this right but I am not sure how to read it right. I have both probes touching the wires that go into the spark plug caps and this is the reading.

I think I don't quite understand what you're measuring? If one probe is in one of the sparkplug caps of a coil and the other probe is in the other sparkplug cap (like, 1 and 4 or 2 and 3) then those plug caps are pretty good. If the probes are in just one plug cap, that one is burned out: it should read closer to either 5.00 (K ohms, which is x1000 times the reading on the screen) or 7.50.

[cr0issqnt]

Yes one probe was in one spark plug cap and the other was in another.

I did take take off the carbs and sprayed around in there today and that seems like it was the fix I should have posted that I had.

[M 750K6]

......... They should be within 800 ohms of each other (if they are around 5000 ohms). If they differ by more than about 1500 ohms, then only one plug of the 2 on that coil will usually fire......

Obvious once you are told, but this by-product of wasted spark systems had never occurred to me.  Thanks for sharing.

[Deltarider]

One could put this to a test: have one R(esistor) plug (5kOhm) and the other standard (zero) and see what happens.