When do you know when you need to re-piston?

[Ross and Alice]

I understand most the 450's have the hardly any skirt and rings pistons that made need replaceing from time to time

How do you know when?

Is it piston and rings only, say in a YFZ, or is their more that needs replacing too?

[dunefreak]

When it goes boom? :rainbow1:

I think whenever it starts getting tired. It kinda depends on the way it's ridden I guess. Then again I have riden the sh*t out of my Raptor now for about 3 years non-stop....all winter at Dumont and all spring/summer at Coral Pink and it still runs strong as hell. ....Knock on wood

[1bad4fiddy]

Like pete said , it will get tired , youll lose power , starts smokin , pull a compression check once in a wile to see how it is

[Mr. Edgy]

A piston, rings and gasket set are cheap insurance on the "new" style four strokes. If you let it go, then your going to have to replace a whole lot more than that. The Honda piston has way less skirt area than the Yamaha. The lighter the piston the faster/quicker it revs. I think a compression check on occasion is a good idea. It is really hard to tell when these bikes are getting weak. It is not like the two stoke that gets tired. Also, sometimes the symptoms of a tired or weak four stroke are valve train related and have nothing at all to do with the cylinder.