77 xs 650 timing trouble

so i just rebuilt the top end and hooked aq battery and have spark. i am now trying to time it. i hooked up a test light to the grey wire (right cylinder) and when i turn the engine over counter clockwise the points touch and the light lights up at what looks to be 180 degrees from where it should. i thought the light is supposed to turn on when it reaches in between the two marks on the rotor that are really close together and on the compression stroke. does anyone have any advice? im confused. i hope this doesnt have to do with how i rebuilt the top end or something. amy videos of someone timing an xs?

This should help: http://www.xs650.com/forum/showthread.php?t=1604

It sounds like you may have assembled your advance rod wrong. The fittings on the ends of the rod have locating pins but it's possible to assemble things 180° off. That throws the timing off that same amount. The locating pins at each end of the rod should align or point in the same direction .....

slayer123 said:

so i just rebuilt the top end and hooked aq battery and have spark. i am now trying to time it. i hooked up a test light to the grey wire (right cylinder) and when i turn the engine over counter clockwise the points touch and the light lights up at what looks to be 180 degrees from where it should. i thought the light is supposed to turn on when it reaches in between the two marks on the rotor that are really close together and on the compression stroke. does anyone have any advice? im confused. i hope this doesnt have to do with how i rebuilt the top end or something. amy videos of someone timing an xs?

Click to expand...

Did you set the timing marks correctly when you assembled the top end?

Alternator rotor mark at TDC.
Mark on left side of camshaft at 12:00 position.
Punch mark on right side of camshaft gear exactly even with top surface of the head.
Left cylinder valves are open on intake and exhaust stroke (tappets are tight).
Right cylinder valves are closed on compression and power strokes (tappets are lose).

There are 3 pins.The 2 pins on the advancer shaft both aline at 12:00 as
5twins mentioned, and the third pin on the camshaft (which drives the advancer backplate) should be at 12:00 also.

If you have as above, then the engine timing is correct.

When the engine turns the points close, this lets current flow through the primary side of coil. This creates a strong magnetic field in the coil. When the points open, the current stops flowing and the magnetic field collapses. This induces a high voltage pulse in the secondary side of the coil. This high voltage pulse is what travels down the plug wire and jumps the gap, creating the spark.
The test light lights when the points are open, it does this because when they close they ground the coil to let the current flow. This leaves the points wire at ground potential, so no voltage to light the light.
When they open the light lights because the points are no longer grounded. This is the point you want to line up with the timing marks.
With your test light hooked up turn the engine till the light lights up. Now keep turning till it goes out, just as it goes out should line up with the timing marks.
I turn the engine so the lights lit, then turn till the marks line up. Then adjust the backing plate to get the light to just go out.
Do the right side first, then do the left side.
Leo

Thanks for all the info i finally figured it out!

slayer123 said:

Thanks for all the info i finally figured it out!

Click to expand...

You can't just leave the story unfinished like this. Since you received helpful information, its appropriate that you tell us what the real problem was. It will also help others if they
run into the same problem.

i was trying to time the points when they were touching in between the timing marks on the stator. i was supposed to be timing them when they were just starting to open on the timing marks.