ATC 90 too much compression?

[MastaFlyMason]

I finally got my ATC to fire up but it wasn't running right so I adjusted the valve clearance. The exhaust and intake were both too tight so I put them to spec and put it all back together. When I went to start it it had tons of compression and was very hard to pull. The second pull it broke my pull rope. Is it possible to have too much compression or is this just how much compression these 90's are supposed to have?

[atc500x]

Are you sure the timing is correct?

[Joseph Farrow]

Do you have a stock cam?

[MastaFlyMason]

The valve timing is perfect unless it is 180 degrees off but as it fires up I do not think that is the case. I checked ignition timing and point gap they both look good as well. And yes the cam is stock

It kind of feels like its yanking back when I pull

[dabody69]

My 1980 110 did the same thing, ripped the pull cord out of my hand, check timing again

[MastaFlyMason]

My 1980 110 did the same thing, ripped the pull cord out of my hand, check timing again

Valve timing?