TDC is a moving target
 

Hello all, I require knowledge;
As I turn the crank (anti-clock) My IT mark gets to within 20mm of the casing mark to line up TDC........and the fly wheel shoots past the casing mark by around a further 25mm.
Iv slowly (reverse) cranked it back in line and securely clamped the socket bar so nothing moves.
Carefully reset the valve gaps and it now sounds terrible (like a lollipop stick in a bicycle wheel but louder).
I have marked-out when the piston is at the top of the compression stroke but this bears little relationship to the timing marks
p.s. The bike did run well until I tried to stop the light tapping noise.
Any ideas ?
Edd

Yes, there are two TDC's one for exhaust stroke and one for compression stroke. You need to ensure the piston is compressing the cylinder and not exhausting. Generally you can feel the compression. It might help to squirt 3-4 drips of oil down the spark plug hole. remember to replace the spark plug before trying to find compression.

sorry I should have said, I had aready removed the spark plag.

I bet you had to really loosen up the adjuster to get proper clearance?
If you watch the rocker arm through the port in the cover(cap out of course) as you turn the motor over you'll see the exhaust valve get pushed down, you now know it is on the exhaust stroke. Turn it one revolution more while watching for the mark, then it is on the correct stroke.

You should never turn the motor backward when doing adjustments. I use a T'bar or breaker bar to turn it over so you can control the motor when it wants to take off.

JJrider, You were right about really having to loosen up the gaps,
I have reset the gaps again, and she started easier and ran a lot quieter, then I found two manifold bolts were loose, sorted them and she is now
quieter still.
I still have this slight metallic tapping at the top (valve cover area) but Hey-Ho I will live with it.
I used a great xt forum in oz (can’t get connected now for some reason)
so I am really pleased to find this forum.
Many thanks for the input gents, it is really appreciated.
Edd.

It’s the link at the bottom of your page, (Mezo, now your name rings a bell)still can’t connect though, wish I could then I’d have 2 great streams of knowledge for XTs.
Edd.