Briggs and Stratton
21cubic inch
8hp
nearly 30 years old

Ive just got a new magneto etc, points gap has been checked and is right etc. Ive got the strobe timing light out and the arrow on the fly wheel is jumping randomly within about half an inch of range.

Is this normal for an engine of this age? I noticed the engine was spewing its guts trying to run. Really sounded like it was labouring and running hot so i checked this. Anyway is this the problem and if it isnt normal can someone please advise a suggestion?
Again any advice or help greatly appriciated ^^
Thanks
Ice

The timing mark isn't jumping. What you are seeing is the timing advancing and retarding because the engine RPM is fluctating.