Have another look on CMSNL at the cam chain adjusting device for your exact bike.
It has an upper bolt that holds the units top to the cylinder head and is the fixed part of the devise.
The spring acts to pull the sliding member downwards, thus making the actual curved adjusting blade more curved taking up the chains "slackness".
The sliding member is "clamped", "locked" by the square headed "bolt" ( which looks similar to a UK 70's /80's ford car battery clamp bolt, the flat terminal battery lead terminals ) which passes thru the cam chain tunnel, thru the tunnel wall and clamped by the nut in the centre of the cylinders cam tunnel.
The nut half way down and in the centre of the cylinder blocks rear, is the auto adjusting mechanism lock nut.
Slacken this nut, clamping effect of sliding part is lost, spring action auto adjusts adjusting blade downwards.
Once this has happened, nip up nut tight.
The adjusting blade is clevis pinned to the sliding member at the top and visible in camshaft area, centre rear.
The bottom of the adjusting blade, the curved one, is held in place via a balance chain slipper bracket and bolt.
I would not auto adjust with engine running, nor would I press downwards on the clevis pin to allow "extra " adjustment.
If you have had the cylinder head off, the front blade's upper "pegs" fit in two slots either side of the cam tunnel in the cylinder block.
The bottom of this blade fits in a trough involved with the balance chain slipper A, but can be fitted incorrectly. If you look down into the cam chain tunnel, you will see the trough. A mirror and torch may be needed.
If you need pictures of these parts and locations, just ask.
Actual component pictures can be seen on CMSNL.
So, cam chain adjustment, engine cold, cam cover off, flywheel cover off, set flywheel to T, slacken the cylinder block central rear adjusting nut, watch auto adjust happen, nip and tighten nut, job done.
How are cam sprocket timing marks, level, or any "lean back" ?
Also, cam chain lift from top of cam sprocket, how much daylight seen between chain and teeth when cam chain lifted ?
I like to ensure the cam chain front run is taught during auto adjust.
When auto adjust had taken place and nut is locked, move flywheel back and forth one degree, not much at all, watch for chain link movement to indicate wear in each link. This is akin to cam chain lift.
It can show wear in the whole drive train. Try to not let the cam sprocket move at all for more accurate wear assessment.
All of this procedure with cam and flywheel covers removed, takes say 10 seconds.
Check adjust valve clearances, my book says clearances for this type of cm 250 could be 0.12mm inlet, 0.16mm exhaust, or, 0.10mm inlet, 0.14mm exhaust cold.
Engine no. Cb250te-2100001 and subsequent
Frame no. Mc05-2400001 and subsequent
Check on CMSNL using your frame and engine numbers, they do appear near the model classification.
I don't have internet other than mobile phone, so pictures will be phone pictures.
However, I can scan and save to Sd card, transport card and reader to an internet pc some distance away and send from there....a time consuming process.
Pictures of the cam area if this bike please.
Is this the bike with head bolt problems ?
Balance chain adjustment as per superdream, have you found the DOT meantioned and after auto adjust, how much adjusting slot remaining ?
The dot position relative to clock face and remaining adjusting slot is quite important.