YZ125 2001 questions

well guys the dream came true and i got a 125. amazingly fast. but ive had it for a few days and i dont know much about it and i have some questions.

1) will riding in midrange help foul my plug?

2) how can i tell when my plug is dying and when its fouled ( besides it wont crank)

3) should i run 50/50, water or pure antifreeze?

4)how do i raise the idol speed? my yz wont idol at all :thumbsup:

5)how often do i need to replace the rings and top end if im going to do NO racing, casual motocross track, harescrambling, and gncc stuff?

1. I have never had a issue with the plug fouling in a midrange

2. as you are riding when you give it throttle you will feel the engine bog even in first gear at low speeds

3. as far as 50/50 i know that full service manual says to use 50/50 but not sure about pure antifreeze

4. the idol speed screw should be right above were the fuel from the tank goes in. Loosen the lock nut, turn the throttle stop screw until the engine runs at the slowest possible speed then tighten the lock nut

5. some people change there piston and rings every 25 hours or so. but who has that kind of money. I think you can stretch it out a little longer then that since your not racing. if you stay off the rev limiter you should be fine for alot longer but to give a specific amount of hours i am not to sure. just judge it on how hard you ride it and how often you change the oil. hope this helps

So how can I tell when I need to replace rings. With the kind of riding I do is a top end a year ok? And rings twice a year? When I bought it the top end was two months old. Also, does a bad plug make it hard to start?

Yes, a bad plug makes it hard to start or it just won't start or stay running. If in doubt, get a new plug...don't mess around with trying to clean the old one it's not worth it. I don't want to get you confused and talk about too much yet but let's get you to a good baseline and go from there:

-Get a fresh plug

-Get some fresh gas and Yamalube 2TR premix and mix correctly at the ratio the previous owner said to (If no guidance, go with 36:1)

-Clean and oil your air filter

-Check your silencer's packing and replace if it's all caked up with gunk or if it's disintegrated

-Start your bike and run it. Did it start up ok? Does it run smooth through the range of throttle and sound good? Yes, then adjust your idle as stated above and have fun. No, then report back with your findings, ie: it's bogging; won't start; starts then dies; etc.

This is just a base but there are other, more complicated and common, things that may need to be done such as jetting, carb cleaning, top end, and so on. More information on that to follow if needed but it sounds like you may have just fouled a plug or forgot to check/clean something since you said it has been running good at some point since you bought it.

I still had questions about the top end and ring. When I got it there were 3 races on it. I checked it today and the compression is great. How often do two strokes go on top ends? And rings? I will not be raciNg motocross, just gncc stuff. I mix premix at a ratio of 32:1. Also, what would happen if I put some of that new antifreeze in (just a small amount) With what could be the old kind? The one in there was kinda yellow and the kind I added is greenish.

I don't think mixing the antifreeze will be a problem but why not just drain the old stuff and refill with new? As for the top end question, you are going to get a zillion opinions on how often to change it. Really, it's up to you. If you have good compression and she is running great than leave it be. If and when you notice lower compression, less power, hard to start...change it out. Or...pick an interval like every 30 hours and it will be cheap insurance for your motor.

32:1 is a good ratio and will help keep the motor running strong, just make sure you ride it like you stole it at the end of each riding session right before you hit the kill switch...that will help keep the motor/exhaust cleaned out which will help with reducing a fouled plug.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now