Topic: Reversed ignition timing/firing 400 F Super Sport

[MDW]

I have been trying to solve a running problem on my 1975 400F Super Sport. I found that cylinder 3 wasn't always firing. I checked a lot of things and got to the ignition. Everything seemed to be set up right but to check the wiring and the advance timing unit I took the ignition apart. Now, putting it together again, I find that the 1/4 points open roughly when the 2/3 points should open and vice versa. I cannot see what I have done wrong but assume it is me and not the bike. Any suggestions? Thanks

[Pbeattie89]

Assuming that the 400f is the same as the 750. If you took apart the advancer unit, you could have the cam lobe 180° out of sink.

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[MDW]

I double checked but the cam lobe can only go on one way. I am wondering if the part of the contact breaker that touches on the cam could be worn?

[bryanj]

Yellow and blue wires are swopped in one of three places
1 points
2 rubber boot by brakelight switch
3 coils

[scottly]

I double checked but the cam lobe can only go on one way.

Are you sure about that?

[Deltarider]

[...] but to check the wiring and the advance timing unit I took the ignition apart. Now, putting it together again, I find that the 1/4 points open roughly when the 2/3 points should open and vice versa. [...]

Let's first concentrate on this. Below you find a pic of a -333- advancer. In the rim of the lobe you see a tiny mark carved in. Are you sure yours faces the same as in the pic?

[scottly]

This pic shows the mark facing the opposite direction, but I don't know if it's correct?

[jonda500]

Plug the blue wire into the yellow and the yellow into the blue - if that fixes it then I'd say your points cam is installed 180 degrees out. Happened to me when I rebuilt my 400 Four.
John

[HondaMan]

Plug the blue wire into the yellow and the yellow into the blue - if that fixes it then I'd say your points cam is installed 180 degrees out. Happened to me when I rebuilt my 400 Four.
John

+4.
Happened to me when I rebuilt (2) CB750s, a CB500-4, and a CB350F.

[dave500]

look real close,should look like this,the marks can be hard to see,sometimes a dot or a short line.

[Deltarider]

Scottly's pic in Reply #6 demonstrates it well: the left, a -333- advancer for CB350F/400F - this one is by Hitachi - has been reassembled wrongly; the mark should face the cut out at 6 o'clock. The one on the right a -300- for CB750 - this one is by TEC - has it right. Note that the mark is very, very hard to see.
The second pic shows a -323- CB500/550 advancer - this one is by TEC - where the mark should face the little hole (in the pic framed in white). Were it one by Hitachi, then the mark is supposed to face the Hitachi logo.
Ofcourse one could just swap the wires, but as I have witnessed, this can confuse the next owner of your bike.
Here's a question I've posted a month ago but never received an answer to: the advancers have openings right under where the springs are. Is this to reduce weight or to facilitate servicing (ofhooking) the springs, so one will not overstretch them on (dis)assembly?

[MDW]

Thanks for all the feedback and ideas. My advancer is below. It looks like the one posted above but doesn't have the hole. Is there another mark to align with?

 Also, I don't think the wires are reversed. I am hand cranking the engine at the moment and watching for when the points open/close. I can see that they open close at the wrong time which makes me think this is a mechanical issue.  I will check it there is any mark on the cam.

[Pbeattie89]

Thanks for all the feedback and ideas. My advancer is below. It looks like the one posted above but doesn't have the hole. Also, I don't think the wires are reversed. I am hand cranking the engine at the moment and watching for when the points open/close. I can see that they open close at the wrong time which makes me think this is a mechanical issue.  I will check it there is any mark on the cam.

Looks like you are 180° off. Happy wrenching.

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[scottly]

BTW, it's an ND (Nippon Denso) advance, not Hitachi.

[MDW]

Thanks everyone - I will try this and see what happens!

[Deltarider]

MDW, would you mind uploading a pic of the backside of your advancer?

[MDW]

Sorry, but it is all back together. If I need to remove it in the next few days I will certainly send the picture and have made a note of your name.

[Deltarider]

Forget it, it's not that important. Thanks anyway. Does it run now?