Timing mark moving the wrong way when revving engine?

ljevans

ljevans

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My buddy and I were starting to play around with the timing on my bike today and we had the mark at idle between the lines of the "F" area but when we revved the bike up the line travelled to the right towards the TDC mark as opposed to the way that I expected to the left towards the full advance mark. Any idea what I hooked up wrong to achieve this?

thanks.
 
You have one that was originally for the southern hemisphere. You'll have to trade it in on a clockwise model.
 
A few things come to mind, but the dominate ones are:

A bad/worn advance unit. Stretched springs and worn weight ears, unit will go to full advance at idle, owner sets idle timing there, then when revved, slotted cam bounces against worn ears and gives retarded timing.

Bad timing light or hookup, circuitry can't keep-up with pulse frequency.

Stuck advance rod.
 
xjwmx---You hit the nail on the head. tim
 
ljevans said:
My buddy and I were starting to play around with the timing on my bike today and we had the mark at idle between the lines of the "F" area but when we revved the bike up the line travelled to the right towards the TDC mark as opposed to the way that I expected to the left towards the full advance mark. Any idea what I hooked up wrong to achieve this?

thanks.
Click to expand...

Post a picture of your ATU ( close up pic of the fly-weights etc.)
 
This was taken the other day before I modded the springs and lubed it up. It seems to be working well now since the arms return to the stop properly and the revs dont seem to hang up anymore. It's just this issue that the timing mark on the rotor travels the wrong way when I increase the RPM
 

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In your picture, and the pics in this thread:

http://www.xs650.com/forum/showthread.php?t=30931

The coilcount of the springs in these pics is 9. Did you remove any coils, making the springs too tight?

There is some wear on the weight ears of your ATU, enough to allow timing bounce, but usually tolerable. Could try check again with timing light and a much higher rpm...
 
ljevans said:
This was taken the other day before I modded the springs and lubed it up. It seems to be working well now since the arms return to the stop properly and the revs dont seem to hang up anymore. It's just this issue that the timing mark on the rotor travels the wrong way when I increase the RPM
Click to expand...

I can't understand how the timing can move the wrong way with rpm increase. When the weights fly outward, the ATU shaft rotates CW, which is CCW on the left side with the points cam. When the points cam rotates CCW it advances the timing.

Here is something to check. Can you rev the engine to 5000 rpm? If you can, then your timing must be advancing in the correct direction. If your timing was going the wrong way (retarding), then you would not be able to exceed 2500 rpm.
 
Yeah it's a real mind bender lol. My buddy and I have a fair bit of experience with cars but neither of us have ever timed a bike before. I just cut the hook off of the end of the spring and then threaded the first coil through the hole on the advance arms. I did one spring first but it was still hanging up at 5000rpm (so I guess this means the timing is advancing the correct way because it rev's smoothly to 5k) so I modded the 2nd spring the same way and that seemed to sort out the rev's sticking. That's when we decided to try to time it. That's when we discovered it was intermittently firing on one cylinder. After some searching we found the suspect wire so I held it in such a way that the bike was running on both cylinders so we tried to time it and that's when we noticed that the timing mark appeared to be traveling the wrong way. It's stored at my work so I'll probably go there and install the repaired coil wires that my buddy made up for me (with the funky y-connector bullets on them) and I'll try to shoot a quick video of what it's doing and ill post it to YouTube and post the link here
 
One time I had to use a light with so many buttons and dials on it that it was just luck it didn't go backwards.
 
I agree. If its running and can rev freely. Timing gun. Mine has an advance dial on it marked in degrees so you could theoretically set advance if you had no mark...only problem is that it moves the opposite way... It retards the flash and im not sure why....
 
Well i went out to the bike this morning and put on the new wires that connect the points to the ignition coils. It seemed to be running better but when i hooked the timing light up to the left cylinder it was only flashing intermittently. I figured the timing light was messed up but I put it on the right cyl to make sure and it seemed to work perfectly on the right. So it seems I now have some intermittant issue with the left side. When I first fired it up today it seemed to be running on both cylinders and it would rev up to 5k no problem. When I hooked up the timing light to the right cylinder before I packed up up for the day I tried revving it up to 5k but the intermittant spark on the left side was now causing some pretty substantial backfires. I got the bike up to 3500rpm or so while shining the timing light on the rotor. The timing mark wasn't traveling backwards but it didn't seem to be traveling forward much if it all. It was in between the "F" marks at idle though. So now before I can go any further I need to sort out why the left side is firing intermittently. Uggh...it might be time for a pamco? On the plus side my AMC reg/radio shack rectfier seem to be charging well!
 
The points on the left side may be faulty....................how old are those points? Points can have oil on the contacts, or oxidized, and higher resistance than the 0 resistance required. A new set of points or better yet a Pamco may be the way to go.

I have an old timing light that only works on the right cylinder. It won't work on my left cylinder.
 
I'm not sure how old they are exactly but I have a new set in with the parts that I got with the bike. I might throw them on just to eliminate that possibility. That's interesting that you had a timing light that wouldn't work on your left cylinder also. I wonder why that is? I'm sure the comparatively low voltage that these coils produce vs newer ones can't help
 

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