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2003 Yzf450f overheating problems

5 posts in this topic

Hello fellow TTfans,

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 :thinking:

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). :foul:

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?) :foul: lol :goofy:

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 :thumbsup:

ps. Sorry about my bad grammar & long post. I hope you will understand.

Edited by Barra8

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What kind of coolent are you running? I have an 06 yz450f and it used to over-heat but not this bad, now i run "Engine Ice" coolent and now it doesnt even think about over heating... hope this helped

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There is no relief valve connected with the water pump. There is a drain port that releases any oil or coolant that leaks past the impeller shaft to the outside so that it can't mix with the other fluids. The leak at the pump may well have been the cause of the overheating, or at least contributed to it. When you say you replaced the pump, what parts were replaced?

SealsLabeledsm.jpg

The seals have to be oriented correctly as shown, the shaft cannot have a groove worn into it by the seal, and the bearing that supports the balancer shaft must be in good condition.

The headers do not normally glow red unless left to idle for an extended period (over 30 full seconds), and then it should only be visible as red in reduced light.

The bikes typically ran slightly lean in stock form, but if it sat for some time while being worked on, you may have a pilot jet partially blocked by varnish.

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There is no relief valve connected with the water pump. There is a drain port that releases any oil or coolant that leaks past the impeller shaft to the outside so that it can't mix with the other fluids. The leak at the pump may well have been the cause of the overheating, or at least contributed to it. When you say you replaced the pump, what parts were replaced?

SealsLabeledsm.jpg

The seals have to be oriented correctly as shown, the shaft cannot have a groove worn into it by the seal, and the bearing that supports the balancer shaft must be in good condition.

The headers do not normally glow red unless left to idle for an extended period (over 30 full seconds), and then it should only be visible as red in reduced light.

The bikes typically ran slightly lean in stock form, but if it sat for some time while being worked on, you may have a pilot jet partially blocked by varnish.

Thank you so much for explaining that grayracer513! I appoligize for not being able to comment on the water pump replacement issue as this is not my bike & i did not replace it. I have not checked the jets for myself so i will be doing this (if my mate allows me ). I did think there is something wrong with jetting myself but as i said it's not my bike. I will be trying all that you said & hopefully this will fix the problem. If not i hope that you have other suggestions as you seem so good at any bike (from reading your posts). :worthy:

Very much appreciated :thumbsup: :cheers:

Edited by Barra8

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Just a quick update to this thread.

I have decided that my mate has put the water pump seals in the wrong way around. I cannot be sure yet because the motor is getting re-built because of a selector issue. I'm 90% sure that this will be the problem but will be letting everyone know the outcome.

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