Basically i traded my "91 suzuki dr 650 a couple weeks ago for this "99 yamaha yz400f. It was running very well and was a ton of fun to ride, but while test driving it was backfiring a lot. After having it for about a week the idle went worse, so i decided to go ahead and clean out the carburetor and give it a nice soak. The jets were in great shape and screws (I've cleaned out a couple carburetors in my past as well as rebuild ed some). After this i put it all back together and tried to start it, but the idle was even worse as well as didn't even hold a second of non-throttle. I then adjusted the pilot screw, but still just the same thing would happen (I did check the pilot screw if there was any junk in it while cleaning out the carburetor and it was all fine). A day later me and my uncle wanted to go trial riding and so i decided to say yes, and now the bike lost a lot of compression and won't even start anymore!!! (The kick start goes down all the way just by pushing it down with my hand!).
- Barely compression.
- Idle bad.
- Spark plug is brand new and tested!
EDIT: I think it might be a bend valve, but im not sure. I really would appreciate any help or advice!!!
Edited by fishtime9, September 11, 2015 - 03:27 PM.