Help- when to replace the ring and piston?

[TRUST]

I bought my bike second hand ( a YZ250), the owner
claimed that the bike was working only between 8-10 hours.
The bike looked totally new and the compression was great.
When should I change the ring? what is the normal frequency for a ring replacement and also for a piston kit?
I barley ride in tracks most of the time in open fields.
also, how many times can I replace the rings?
thanks

 

[TRUST]

O yea, and what about gaskets and O-rings?

 

[hot125mod]

it all depends how you ride and how you maintain your bike but on a 250 generally 15-20 hours for a piston and 7-10 hours on the ring. now if you have a bunch more compression that is going to change and need to be done more often. keep an eye on the head gasket/orings and always use new ones when doing a rebuild.

 

[Lee172cup]

Hi, I have a 02 YZ125. I've had it 6 months now, riden about 8 times on mx practice tracks. How often should I be changing the piston etc? Is it more or less often than on a 250? Also, what actually happens if the rings or piston 'go'. I've know it can be quite expensive but I'm not very mechanically minded so don't fully understand.

Thanks

 

[Redrodent]

40-50 hrs of trail use you had better check it. Don't count on just a re-ring. Usually posts like this are full of responses " I should have checked it sooner".

I just did mine at 60hrs. Famous last words - it ran fine. The side power valve was broken, reeds didn't seat, piston skirt was worn out, and you could have fit a nickel in the ring end gap.

 

[VISaki]

not for my kx 100 just re ringed it checked rod clearance side play and up and down play still solid...piston is still good..so is cylinder I use 2 types of oils one thats thicker and one for performance every other gas fill..and she still runs great.

 

[2strokerfun]

It all depends on how you ride, how you take care of it and how it was put together in the first place. Some trail riders can go 2-3 years on a piston and rings. Racers, no way.

 

[rmc_olderthandirt]

Gaskets don't need to be changed on a preventative basis and you should always use new ones when you have taken something apart.

If you replace the rings before something bad happens it will be an easy job and only the cost of gaskets and rings. You also get the opportunity of doing the work on your schedule.

If you wait until the engine stops running:
a) If you are a long way from your truck, you could be in a world of hurt.
b) It definately will not be a good day
c) The cylinder will sustain damage, requiring some combination of sleeving, boring and/or plating which can cost hundreds of dollars.
d) There won't be any option but to change the piston.
e) other parts could get damaged, such as the head or even the bottom end.

Rod

 

[mkelly04]

Everyone is different. There are so many factors involved it is hard to say when you should change the piston and rings.

Obviously the harder you ride the more often you will want to replace the piston and rings.
A C class mx rider could probably get 40+ hours out of rings and 80+ out of a piston.

I know I could get 80 or so hours on my 250 and everything was within spec.



My suggestion would be to tear it down at around 30-40 hours. While it is taken apart you can get an idea of how much wear you are putting on the bike and then you can adjust your maintenance intervals accordingly.