I've been reading this forum for couple of months (even before I got the bike) and realised it's an endless well of knowledge.
I bought '04 yz450f 3 months ago. Bike pulls like crazy, I barely have strength to ride it longer than 1 hour .
When I was purchasing it,the bike ran really well. It still does, but I've got couple of questions. I read a lot of topics concerning lots of usual and unusual things these bikes tend "to do" .
Just after I bought it, the engine was running really quietly and there was no any rattling noises I could notice. Just SUPER rhytmic bang sound, that the engine makes when the gas is exploding in it. I was impressed - 10 years old bike running like brand new.
The guy who was selling it told me that the last investment he made was the new piston. Bought it with 30hrs after replacement.
After 10 hours of really soft riding the engine started to rattle. I was really worried about it, but I found lot of info here, that these bikes just do like this. (it wasn't very loud or making me think it's gonna blow - it just appeared and made me suspicious)
The idle rpm started to swing a little bit and sometimes (depends on the weather and if the bike is warmed enough) the rpms wouldnt go fully down just after reving the bike (it stays on something like 1/8 of throttle and when u rev it couple of times it goes down to idle)
Few days ago I decided to check valves clearances. all three intake were .15mm and the exhausts were .20mm.
The cam chain slack and tensioners eject level (60%) made me suspicious. I decided to change the chain and the tensioner (i thought that the new one will work better, but it's the same way - the only difference is that the old tensioner has "1" casted on it and the new one has "3")
Should I stay with the old one?
The old chain wasn't stretched when I compared it to the new one. The only difference between those 2 is that the old one isn't bending smoothly, just like the new one does. (finally a good decision )
I took off the rear chain guide (thanks to Grayracer for the instructions )
The main question is:
does this guide needs to be replaced? (look at the pic)
The surface where chain slips on is kind of wiped. The rubber thing that covers the guide is much thicker on side and the back of guide than on the "slipping surface". Actually I checked it with my tongue and teeth and it seems that its 3/4 thicker than the "slip surface" (anyway, there's still some "rubber" on it).
BTW: Can the floating rpms cause the rattle to appear? (it caused the engine to run not as EVENLY as it did on the beginning)
PS: I found this scar on the bottom of left crankcase, beside this rectangular passage. Will it proceed fast? It's a 1mm deep groove.
Edited by sosycz, August 25, 2014 - 12:07 PM.