timing mark moving while idle...

[schioler]

hey guys ..
i have been looking at my timing marks using a timing light,
and i can see that the mark is moving in idle, is that normal,
if not - what can cause this?

thank ..

 

[xjwmx]

It shouldn't change unless the rpm changes. As the rpm changes (increases) it should move in a clockwise direction. What kind of ignition do you have?

 

[schioler]

its stock ignition that i have .. i just wonder, it bounces a couple of mm to each side..
hmmm .. its going to be rebuilt this winter with new ignition - but i just wonder about the timing bounc tho

 

[xjwmx]

a couple of mm

But what year stock ignition? '80 and later is electronic ignition. Personally I wouldn't worry about a couple mm if the bike ran ok. I'd be curious but I wouldn't worry. When I've looked at mine with a light I think it was pinned solid, but maybe not. I had a car that jumped more than a couple mm but ran fine.

As somebody said to somebody, if you want to worry about something worry about your headlight going out at night in the countryside

 

[schioler]

its a 77 stock ignition ..

 

[xjwmx]

Ok, points then. I don't know much about points but I wouldn't consider it a problem myself. Maybe a little looseness in the advance. Or maybe normal. How's it run, and are you trying to make a racer?

 

[schioler]

yeah .. i guess your right.. well - right now it blops and misfires..
i think it is a lean issue - i am getting to that when the bike has been painted and modified... no - not building a racer .. more a bobber kinda bike ...

 

[NONclow]

A loose or stretching cam chain could cause a wandering spark.

Put a new cam chain, front guide, and possibly tensioner on your parts list for rebuild... "Blops and misfires"?... Have the carbs been worked on?

 

[schioler]

i will add that to the parts list ..
i have cleaned the carbs -bu have not been adjusting them at all..

 

[gggGary]

Have you adjusted the cam chain? Yes some wander at idle is normal. "Some" wander even at higher RPM is to be expected, the cam chain and the valves ramping up and down the cam is the prime suspect.
I like WER's? cam chain adjust; at idle tighten till the adjuster JUST stops moving back off 2 flats (1/3 turn) done. If the adjuster is moving in and out a lot that is the valves moving the cam chain slack from the front to the back and that's the cam and timing moving too.

 

[schioler]

thanks man...
i will check the cam chain and adjust if needed....
afterwards ill adjust the valves

 

[gggGary]

Here's a good thread on doing that stuff.
http://www.xs650.com/forum/showthread.php?t=13083