Need help on what's wrong with my cr 125

[Bobby_Josey]

Hey I'm new to this but I have a 2001 cr 125 that I just bought and it's a nice bike but when I ride it it feels like the powerband doesn't kick in and read about problems and where the exhaust hooks up to the motor it leaks a little bit and I read that it might be the o rings but I'm not sure if that's what it is. Help please

 

[High Lord Gomer]

Many CRs (not sure about the 01 CR125) had o-rings to help seal the exhaust.

Checking is made much easier using an exhaust spring puller:
http://www.motosport.com/dirtbike/p...g&matchtype=&gclid=COfcxPPkkLwCFZPm7Aod9lwAVg

How high are you revving that thing? 125s don't get into peak horsepower range (powerband) until fairly high RPM.

 

[Bobby_Josey]

I've been riding bikes for a long time and I ride it just like any other 2 stroke but the powerband just won't kick in. I'm gonna replace the o rings and everything but I've heard that it could be the jets or it could be idling screw or it could be the power band needs to be replaced but I honestly don't know.

 

[arnego2]

The powerband needs to be replaced?

I think more likely the Piston needs to be replaced. How old is the top end? Almost all seller will tell you it is new but unfortunately they tell not the truth. :(

 

[Bobby_Josey]

I bought the bike and the guy said the bike just got rebuilt but there no way it has but I'm thinking about taking it and getting a full top and bottom rebuild so I know everything right on it. I think that would be the smartest thing to do at this point.

 

[arnego2]

It is easy to see if yes or no, take the pipe off and have a look through onto the piston.

 

[dirt bike dave]

Check to make sure the power valve (aka the variable exhaust port) is opening properly. Not sure about the 125, but the CR250 has an inspection plug that you remove. You rev the bike in neutral and can verify that the power valve is opening.

The power valve staying closed will make the bike run as you describe.

 

[High Lord Gomer]

I've been riding bikes for a long time and I ride it just like any other 2 stroke but the powerband just won't kick in. I'm gonna replace the o rings and everything but I've heard that it could be the jets or it could be idling screw or it could be the power band needs to be replaced but I honestly don't know.

Sorry, didn't realize your level of expertise.

You're probably right. I would replace the powerband. It might be tough to find one for that year but I have heard of people using KTM powerbands in CRs. They are a little wider but still fit.

 

[RM_guy]

Powerbands are also tough to locate at this time of year. The cold weather makes it difficult to hold the tight tolerances that are needed to make them so they can only be made in warm climates. Unless you want a blue powerband because they run colder.