I need to brag a bit being that this is the first time I've ever done a project this big by myself. I took my 04 YFZ450 to the Silver Lake sand dunes in Summer 2011. The air box fell off and sand destroyed the cylinder/piston. The quad was given to me by a friend going into the USAF and it wasn't maintained very well to begin with.
I spent last spring, summer, and most of fall rebuilding the top end and learning everything there is to know about these quads. After all was said and done, I had $1320 into a 478 big bore kit, new titanium valves, starter, solenoid,gaskets and o-rings, and timing chain and slides. I had the piston coated at Line 2 Line for a good 2/1000s clearance and better compression.
I thought that was the end of it. After we got it all back together, it ran for a few minutes and came to a screeching halt AGAIN. WTF!? The crankshaft assembly had seized up completely.
I ripped it apart again and had my mechanic friend help me with the lower end because we all know how much of a doozy those trannys are not to mention all the syncing that has to take place while building it back up. I replaced the old with the new. A Hot Rod crankshaft asy, hot rod crank bearings, Wiseco clutch plates, gear stator gear case cover (cracked in previous reassembly of motor), battery, new front and rear sprocket and chain, lots of oil to flush the metal shavings and crap from the lines, new filter, and jets. Thus bringing my grand total to $2,065. FML. Parents aren't happy. I don't care, I was in too deep already.
Definitely worth it! After lots of breaking in in first gear around the neighborhood, I got it up into 3rd gear and she's still lifting up in the front!
Can't wait to see how it really performs out there. There is an excessive amount of torque and power like I have never felt from a 450, even the newer Bill Balance that my friend bought new (but I do envy his fuel injection).
I call it a sleeper quad because all the modifications are unseen. The plastics are sh*t and have white stress marks and will eventually be replaced. Tires are God awful and are 10 years old. My best friends cousin hit a tree at 40+ mph and demolished the front bumper which in turn ripped a weld point from the frame. That will get fixed soon. The frame itself looks like it has been sitting in a sand blaster too long. The exhaust will get heat wrapped or coated at Line 2 Line.
All in all, it may not look pretty, but it'll definitely kick some ass! Warmer weather would be much appreciated at this point!