5,500rpm saw me out in my GX engine. It could rev more, but i dont abuse my engines & this one rewarded me with spirited performance & long life. It was a fair deal.

If the flywheel is less than fully tensioned, the harmonic frequencies at critical rpm's cause it to "chatter" This damages the six little bolts & the problem just deteriorates untill all six bolts break. It also messes up the flywheel & can hurt the crank too.
Many "A" engine racers have learned this the hard way.

The embarrasment of having it towed home will be relived every time one of your friends with a Toyopet reminds you of it.
[Toyopet became Toyot..aargh.]

The chances of it being a timing chain is probably somewhere between slim & none.