Electronic Ignition Timing - how TF to use

T Mac

XS400 New Member
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Edmonton, Alberta
Hi all,

New to the XS forums but long time rider / tinkerer. Recently picked up a 1981 400 and did some light work on the top end. Previous owner obviously didn't know how to insert a spark plug without ruining the threads :geek: Anyways, everything is buttoned back up and engine is in the frame. It is time to time the bugger.

I must say I've never come across a timing system like this, and so I have real difficulty understanding how to set it. I've reviewed 2 different repair manuals - both found on this site, thank you! - but I still don't understand. I've also searched this forum and found some descriptions on how to do it, but it's still not making sense. A

I get how to take off side cover and position piston, but can someone please explain to me - like I'm a 5 year old - how TF do I static time the L and R cylinder????:bow2::bow2::bow2::bow2::cheers::cheers: A picture or video would be worth a million words!

I should add that the manual recommends a static, not dynamic time, so I haven't bought a strobe gun or anything like that. I have a multimeter and just need to figure out how to use it in this case.

Any help would be greatly appreciated!!!!

Here is a link to the static timing: https://www.xs400.com/threads/breaker-help.20605/#post-186626 look at post #8.

1. You will have to rotate the engine over until you are on the "LF" mark in the timing window. The rotor of the pickup should be positioned with the punchmark on the upper side of the rotor, if it is not, roll the engine over one more turn and back to the LF mark.
2. Rotate the backing plate of the coil until the rotor and coil line up like the picture in post #8 above.
3. Tighten down the screws for the coil backing plate and the static timing is done.

You will now need to start the bike and use a timing light attached to the left plug wire to fine tune the timing. With the bike running at idle, the timing light should show the LF mark in the timing window. Rotate the backing plate of the pickup coil to get it on the mark.
Thanks so much, CaptChrome! It makes sense when you explain it - maybe they should hire you to write these repair manuals!

The way I'm reading the instructions we only have to set the LF timing, and the right cylinder timing is just coordinated with LF so it'll be in time once LF is set. Is that right?

Well I followed your instructions as I understood them and the Ol' XS fired right up. She's only running on the right cylinder though, and I'll be checking for spark, fuel, etc. later this evening. I'm guessing timing is OK (not perfect) and the issue is elsewhere...
You are correct that if you set the left cylinder, the right will be timed correctly (this is only for the OEM electronic ignition, breaker points ignition systems usually have some adjustment for both cylinders.) It sounds like you are over the first hurdle and indeed, you will have to check other components on the left side. Be methodical and don't rush it.