CB500 Ignition Timing Puzzle with added YouTube video

[Rob.b (Rob Birkett - RIP)]

Hi all I have just put the engine back in my bike after a major and excellent overhaul.

The first start up was a bit of a faff, before I pressed the starter I checked for spark and put in new fuel, at first all it would do is spit and fart occasionally.  In the end I decided to check the timing and this is where the puzzle is, It is 180 degrees out, which I think is impossible, so I swapped the yellow and blue wires over where they connect near the battery and hey presto it runs perfectly.

I have put a vid on YouTube that shows whats going on; watch it here and sorry about the sound quality:

https://youtu.be/zJ2kpJkyeoM

Back in October when I took the motor out I decided not to disturb the electrics and they all remain as they were.  Apart from the electrics behind the left hand side panel where cleaned up the contacts.

Any ideas why the points open and cylinders 1 & 4 spark when the timing marks in the auto advance unit are at the 'F' mark for 2 & 3.

Thanks for looking

Rob

[mickwinf]

when the camshaft timing was done did you make sure that cyl 1 was at top dead centre on the compression stroke. if it was on the exhaust stroke would be 180 degrees out so needing the points to match by swapping them over as you describe.

[Johnwebley]

initial thoughts are maybe the blue/yellow wires are conected to the wrong coils ?


 need to remove the tank to sort that

but,it does sound sweet !!!

[deltarider]

Did you have the advancer dissassembled and then assembled the cam 180^o out? Check the pic and if the little carve in the rim faces the hole (both encircled white).

[Rob.b (Rob Birkett - RIP)]

Did you have the advancer dissassembled and then assembled the cam 180^o out? Check the pic and if the little carve in the rim faces the hole (both encircled white).

Ah!! I had no idea that it was possible to remove the cam from the auto advance unit, if this is possible I should be able to alter is position by 180 degrees and in that case even if Mickwinf's observation about cam timing is right I should be able to correct it with the auto advance cam.  Fingers crossed.

I can't get in the garage now cos apparently I have to go to the garden centre, as there is an "unmissable" offer on mulch.  But I will report back ASAP. (on the bike not the mulch).

Thanks Rob

[mike the bike]

I was going to suggest that, having done the same thing myself.

[zed]

me too , i took mine apart as it had seized & when i put it back together was 180 out

[Rob.b (Rob Birkett - RIP)]

Did you have the advancer dissassembled and then assembled the cam 180^o out? Check the pic and if the little carve in the rim faces the hole (both encircled white).

Smack on the money. Thanks too to Mike and Zed. Sorted.  Just need some nice weather now; not for the bike you understand but I've got 240L of mulch to spread on the garden.

Rob

[Nurse Julie]

Well done Rob, now get shovelling