let me explain.
if the crank key is , sheared then timing marks are just useless.
if that is true, the looking at them , is wasted effort. (just a heads up on this common problem .)
the bottom key, on the crank must be PEFECTLY straight up , at the same time as the bottom cog , pointer is straight up , and pointing to the oil pump TDC mark.
3 things on the crank MUST line up. if they dont the key or the keys slot is mangled.
if i found my IGNITION timing , to suddenly be way off, id panic and not run the motor.
surely..
it dont just get up one morning and say , gee, it think ill drive my owner crazy and jump 10 degrees off. (but in your case, your PO might have been Guessing)
it goes off for only 2 reasons.
belt slip a cog.
or
key way munged, on the crank.
or
crazy PO (prev. owner,sorry)
This is the 1 photo that counts.
http://www.kick-fix.com/t-belt/16v-cog-crank-off.jpg
see the key , see the white arrow , this dont lie.
if the cog is timed correctly
and the belt and cam is timed correctly
and the dizzy is off ( timing IGN way off) then someone timed the dizzy with the cam timed wrong.
time to punt.
start at square one.
more photos that can help.
http://www.kick-fix.com/t-belt/16v-crankkey1.jpg
actual 8v;
http://www.kick-fix.com/t-belt/crank-cog-8v.jpg
http://www.kick-fix.com/t-belt/snout.jpg
on some motors.
if you take off the big 17mm flanged blot above
you can not see the key way. unless you pull the cog.
the 16v is always viewable with bolt off.
Now for you:
check the belt timing.
if the belt is timed at the 4 points.
next pull the 17mm bolt.
try to look at the keyway, see if it points straight up exactly.
8v
firing order.
1,3,4,2, and the ROTOR rotates CCW.
ok.
compression is good.
just retime the dizzy and pray
but first torque the crank snout to 94ft/lbs , in the hope it is still good .
How to set ignition timing
break a leg , and WELCOME !!!