Ok guys I will try to keep this is short and sweet as I can. I bought a 2007 yfz 450 from a guy for 800 bucks but it wasn't running. The guy told me that he had stroked it and big bored it. (More to come on that) I have been working on quads and dirt bikes for a long time so no big deal. Anyways got it back home and discovered that the resistor in the electrical system was destroyed. So I replaced that and it still wouldn't start. Checked the valves for correct shimming and sure enough they were way off. Fixed that and it still wouldn't start. So I push started it and it fired right up. Rode it a little bit and it seemed to run very good except a ton of blue smoke / oil was coming out of the crank case breathers. So I shut it down, I then tried to re-start it with no luck. Push started it again and no problem, started up but still the smoke and oil. Next I took the top end apart and discovered that the piston ring was stuck on the piston, not bad, just enough to no spring out. While in the motor I verified that it has a Hot Rods +3 MM crank and a 98MM big bore. I ordered a new 98 MM Wiseco piston rings and gasket set. I also took the head and jug to a machine shop and they verified that the valves and jug were still fine, no leaks, scratches etc. Next I put the bike back together and it fired right up however this is where the problems begin. So, I rode it around for a while and it seemed fine but I quickly noticed around 1/2 to 3/4 throttle it would cut out or break up however you want to say it and the head pipe was getting very hot. (After cooling it's very blue now) So jetting must be the problem..(Also I am at 4000 ft altitude and it was about 85 degrees out)... I opened the carb and discovered that I have a 168 main jet, a 45 pilot, stock needle on the 4th clip. I immediately changed the main to a 180, needle to NCVQ on the 4th clip position. Went for a ride and it starts perfect, Idles perfect full throttle perfect, 1/2 to 3/4 was worse. So I put a 170 main and tried that. Same... Moved needle to the 3rd clip and it was better but still breaks up. Moved the needle to the second position and its much better but still breaks up from time to time. So my question is WTF??? I know 4000ft of altitude makes a difference but there is no way that a 501 can need to be that lean and it is still telling me leaner. I'm thinking about putting the 180 main back in and the stock needle on the 3rd clip to see what happens. Also running 100LL Avgas. Also I have tried lights on, lights off no difference. Tried putting the choke on but it makes the quad run like crap in all throttle ranges. And it always starts the best if I don't use the choke at all and just give the throttle 1 blip before I start it. Any help or ideas would be super appreciated!
2007 YFZ 450 SE (501)
Hot Rods +3 Crank
Wiseco 98MM Piston and rings
Full CT Racing Exhaust
Full K&N Intake (Filter and plastic tube that connects to carb)
170 Main Jet
45 Pilot Jet
NCVQ Needle now on 2nd Clip from top
18" Maxxis RAZR's
15 Tooth front sprocket
38 Tooth rear sprocket
2007 YFZ 450 SE (501)
Hot Rods +3 Crank
Wiseco 98MM Piston and rings
Full CT Racing Exhaust
Full K&N Intake (Filter and plastic tube that connects to carb)
170 Main Jet
45 Pilot Jet
NCVQ Needle now on 2nd Clip from top
18" Maxxis RAZR's
15 Tooth front sprocket
38 Tooth rear sprocket