Alright so I picked up this 2001 CR125 for 900 bucks, and it is Absolutely mint, with a whole lot of aftermarket stuff. Thing is, the guy who owned it before me was honestly pretty unintelligent and I could tell that he's the type of person who just rags on his stuff. He said it has a 'brand new top end with less than 10 hours on it', but he raced. I just trail ride and go easy on the bike. First thing I did when I got it home was take the seat off to take a look at the air filter and as i suspected it might be, it is atrociously dirty and very very dry, as if there was never even oil on it to begin with. So other than replacing the air filter, should I check the cylinder and stuff to? It runs absolutely perfectly, but i'm just sort of worried about it blowing up. Thanks for the help.

Oh and if I'm just going to be trail riding and stuff, how often is reasonable to replace the rings? And i usually mix at 40 or 50:1 to avoid fouling plugs, since i'm not in the powerband that much anyway.

nobody?

just run between 32:1 and 40:1 its not alot of difference and if its jetted right you wont foul the plugs. 32:1 is whats in the manual and works fine for me and keeps the engine correctly lubricated. you can have a mechanic perform a compression test for worn rings etc, an also check the wear on the piston i think through the exhaust flange.. mine was making a metal rattly scraping sound when the big end bearings were almost toast.. has had a full top an bottom rebuild now.

dirtbikenewb, on 06 May 2012 - 05:18 PM, said:

Don't correct jetting issues by changing your mix ratio.  Pick one ratio and stick with it.  Learn to jet your bike, it will be a lot easier for you.  If you don't have a manual, get one.  It should have a chart for changing your jetting based of temps and elevation.  

Read this "how to" on jetting.  Very informative.

http://www.thumperta...rich-read-here/

Alright but any ideas about the airfilter/piston ring wear? Because that's mainly what i was trying to get at