I have a few questions which is a first for me on here but before i do i will describe the problem. I have already read the FAQ's & searched but nobody seems to be having this particular problem.
My mates 2003 YZ450f has been having a lot of overheating problems. He re-built his engine with new everything. By this i mean he replaced everything possible (needed). The list includes...Wizeco high performance piston & rings,valve stem seals,valves checked & re-seated/re-shimmed, all gaskets,water pump,new radiators (the welded tank alloy type),timing chain & i think that is all but maybe i forgot something [color=#011A4D] [/color]
After maybe 1500klms riding it it overheated BADLY & blew the head gasket. I had suggested that it was running too hot earlier (before the head gasket blew) but he said he had checked online & nearly every post was pointing to the fact that ''these engines glow red at the header pipe'' & usually run hot.. Most views were from this site so i hope this will not a spark a repeat of this. When his head gasket blew I had a ride myself. I had ridden this bike before so I know what these things should do. Symptoms included overheating (obviously),header pipe glowing red,water coming out the bottom of the water pump (apparently there is a relief valve there) ,backfiring when throttle was let off,had the power of a 250 (just),hard starting, blown head gasket (eventually) . After a short ride on it i knew that the timing was wrong (not to mention the head gasket blown).
He then disassembled the bike only to find out i was right about the timing being out. So he replaced the top end gaskets,water pump (for the second time) replaced the radiators (mentioned above), new coolant ,cleaned air filter/oiled (again) got the timing right (with my supervision) & it ran great!. No wrong valve timing problem!
After maybe 120 klms the overheating problem started again & is still happening (poor him).
Water still pours out of the ''apparent'' pressure relief valve at the water pump (my mates words not mine) & it looses a lot of coolant
He doesn't ride tight tracks so it's fair to say it's not from air circulation/venting?
He doesn't even have to ride far for this to happen (20 klms max)
I am from Australia, temp is usually 17-40 degrees
Altitude:930 metres (3,050 ft)
Oil used: Castrol Activ 4T 15W-50
No mods have been done other than the Wizeco piston (hardly a mod). Has standard jets (as far as i know)
Because i do NOT own one of these bikes i haven't got much of a clue as to what is STILL causing this. So.....
1.Does this bike run rich from the factory or should he change his jets given that he now has a high performance Wizeco piston?
2. Do you think the valves could have gone out of spec from the heat/timing wrong beforehand?
3. Or is it the water pump (again) or cooling system?
He has spent so much money on this bike & he deserves better from it. It would be such a shame to see it get lit on fire & burnt (maybe a good an idea?) lol
All suggestions are welcome & will be taken into account (if practical) even if the problem is not listed.
Maybe this one will get chucked in the too hard basket but worth a shot.
Thanks in advance for taking the time to sort this
ps. Sorry about my bad grammar & long post. I hope you will understand.
Edited by Barra8, February 19, 2013 - 09:27 PM.