Rings ?

[cwill83247]

Sorry may seem a simple question for most but how can you tell when your rings need to be changed ?

Do u. Have to take top of head of each time to check .?

[lewis cosgrove]

Some symptoms can be loss of power, low compression, smoking exhaust and fouled spark plugs. If your not sure you could check the piston for "Blow back", this is when carbon deposits build up below the rings. If so the rings are worn and should be changed.

[dadof2]

On a two stroke the first signs are loss of compression (easy to kick over) and loss of power. To check properly you have to take the barrel off, measure the bore and the piston ring end gaps.

[feetupfun]

the best way to do non-invasive condition monitoring on the effectiveness of the rings in a two stroke is to look at the surface of the cylinder, looking for carbon deposits (brown smudge) in the area wiped by the rings. If the rings are leaking there will be a thin film of carbon there. You can use an endoscope through the plug hole, a torch or endoscope through the exhaust port, or take the head off to check this.

If you have owned the bike from a time when you are sure it had effective ring sealing, you should be able to tell that the rings are worn by how hard it is to push over compression, and if the low-RPM end power has reduced. Some 2 stroke trials motors develop a 4 stroking/misfiring mode above mid RPM when the rings are worn out, but this is not a universal symptom.

Sometimes it is necessary to rebuild the top end based on piston wear, even if the rings are still sealing OK. For this you will also need to have known how quiet the piston was originally, or to pull the cylinder off and do some measuring.

[0007]

If you don't have a clear symptom then you don't have a problem

Typically: the piston being aluminum will wear at the very least the same rate as the hard steel ring, it's unusual in a 2T to just re ring for wear

if there are a lot of hours on the motor and it's just worn out then it will act rich and rattle

The piston being loose in the jug and the ring being worn so as to loose compression

Rings can be damaged on break in or lose spring tension or distort due to overheating which could cause a loss of compression without being out of spec end gap wise, in this case you would measure Free end gap

So if your engine seal is not weak ie loss of compression / gradual rich ending of the mixture and needing to jet leaner than other riders/bikes and corresponding rattle, then there is no symptom = no problem