125-200cc when to rebuild?

what are the tale tale signs to rebuild the top end before causing more serious problems? how about a very faint ringing sound while in the power band?

Compression test comes up low is a solid sign.

I just got 92.4 hours out of my 165 kit before re-ringing it. It was still running strong, I just felt guilty, so I had to do it.

very faint ringing sound could be anything, and doesn't point to anything in particular.

That's right...ringing can be jetting, vibration or pinging from low octane gas.

Usually when the bike is hard to start and won't idle then it is time to look at the top end.

good. just put the lectron yesterday. just a jaunt down the driveway so far but idle s great. we'll see if the ringing persist soon. just wanna make sure i don't blow it up like my buddy did his ktm 200. he's looking at a $1000 rebuild.

I had a ringing sound like that for a while, it ended up being a broken pipe on the inside of the rear mount where I couldn't see it until I had the pipe off.

Later,

Why not do a compression test?

Faint ringing sound is very often the top shock lock ring has come loose and is "ringing" around!

Compression check against new, and engine hours are a good thing to go by.

Get an hour meter when you do your next top end.

Symptoms of requiring new top end:
- Lack of compression : easiest is to crank the motor by hand using the kickstart..if it's easy to kick by hand (or you don't feel a strong compression stroke), then it's time.
- Piston slap: hard to hear when started but if you pull the head off and you push the piston side-side and the crown touches the cylinder wall, it's time.
- Gradual loss of power: could be carb but likely gradual loss of power is due to loss in compression.

Of all the symptoms, piston slap is the most worrying as the likelihood of a seizure is more pronounced and it is doing damage to the cylinder wall!!

If you are worried, just do a top end rebuild and enjoy riding it rather than worrying (that's what the hour meter is for :P )!!