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mdem07

over heating 07/yzf450

29 posts in this topic

I've got a 07/yzf450. It's only been ridden about five times . Every since new soon as it's started and has ran for 45seconds ,water starts coming out of the radiator overflow tube . Everyone that i talk to ,shop mech. ,friends that are use to the fourstrokes say it's running to lean . So i being new at the fourstroke thing fattened it up . First the fuel mixture screw had to be changed to so that i could make the proper adjustments while the bike was running like the manual instructed with the idle scew . Still water out the tube. So i changed the pilot jet ,went bigger, still water out the tube . So i raised the neddle one notch , still water out the tube . So went bigger on the main jet , still water out the tube . The bike needed the carb mods i guess because it runs better than before ,but i still have water . What if anything should i try next?

Thanks in advance !

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So how much water are we talking about? If you fill it right up to the top of the cap, it is normal to blow off the top inch ( and it never gets any lower than that).

Is it really over - heating?, or just losing the top 3/4 inch of fluid. And, I assume you are using the factory mixture, and not straight water.

Elevation?

I ride an 07 with stock jetting in over 100 degree heat, and have never had it over heat.

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i think your rad cap is faulty, i run stock jetting for the all 8 months a year i ride.

but jetting should have no effect on why you are over heating.

overheating can happen if you are idling your bike without air movement under the rads.

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Thanks for the replies ! I ended up taking it to Yamaha of San Antonio , TX. shop. The staff at that store were very friendly , knowledgeable . The mech. started with the rad. cap ,then romoved the cover and checked the water pump area to make sure everything was ok there . Then he checked the torque on the head bolts , where he found that they were not torqued at the proper specification . So he toqued them , started the bike again and it run at idle for about 4.5 minutes before any liquid came out at all . That's alot better than 45 secounds ! At least now i don't have to wonder if my bike is going to catch on fire waiting for the 30 secound board to go sideways !! Thanks again guys for the input !

1985 ama pro mx nat'l # 48

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Thats what i put in the bike after a friend told me about it. It didn't seem to help at all . After finally checking everything that everyone on here suggested and that didn't work, I took it to San Antonio Yamaha where the Friendly and professional staff worked the problem out. They started with a new radiator cap. That didn't work so they looked at the water pump and that wasn't it so the tech. decided to see if the head was torqued to the right specification . It wasn't so he tightened it. The problem was solved! Thanks for replies hope my findings might help one of you out there.

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decided to see if the head was torqued to the right specification . It wasn't so he tightened it.

:thumbsup::p:cry: that's not good, any ideas how the head got loose?

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:thumbsup::p:cry: that's not good, any ideas how the head got loose?

True that, and once a head gasket let's loose and starts to leak I doubt a re-torque is going to work.

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What is the evidence of that?

This will go down as one of those old stories we tell around the camp fire. I have never, and I repeat never, had this stuff stop an actual overheat problem.

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I was expecting someone to say that the evidence is that it doesn't boil over, but that only means the boiling point is higher, not that the engine really stays cooler. I have an even better question, but it's purely theoretical.

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I guess is was loose from the factory. I have only ridden this bike about 5 times and it has done this from day one. They must have put it together on and Monday or a Friday afternoon around quittin' time....LOL

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As far as the head being loose and leaking, there was no evidence of the bolts being loose. There was no leakage. The bolts were just not torqued to specification. Time will tell if this corrected the problem. Going riding this weekend.....will update after that.

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inquiring minds want to know......what is your theoretical question.......or have you forgetten???

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inquiring minds want to know......what is your theoretical question......???
"Is it good to run an engine as cold as possible?" (assuming the oil is warmed up)

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Well you have to run it warm enough so the fuel stays relatively vaporized and doesn't condense on surfaces but that's pretty cool. You don't want droplets of "cold" fuel in the combustion chamber. At what temp is the oil warmed up?

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Oil is serviceably warm at about 170.

Let me put it another way. Is running the engine at a continuous coolant temp of 230 better or worse than running it at a continuous temperature of 180?

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Oil is serviceably warm at about 170.

Let me put it another way. Is running the engine at a continuous coolant temp of 230 better or worse than running it at a continuous temperature of 180?

Theoretically speaking your engine will perform better at 180 than 230. Whether this is true in an actual situation, I don't know. Odds are the performance difference would be minute.

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The more you vaporize the fuel and keep it mixed with the air, the more it works to the advantage of getting all the energy out of the fuel. A hotter temp will help keep the fuel vaporized and mixed better along it's path to combustion allowing a more consistent fuel mixture. All this would be good for mileage. I'm not sure it applies to getting power out of your dirtbike though.

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The more you vaporize the fuel and keep it mixed with the air, the more it works to the advantage of getting all the energy out of the fuel. A hotter temp will help keep the fuel vaporized and mixed better along it's path to combustion allowing a more consistent fuel mixture. All this would be good for mileage. I'm not sure it applies to getting power out of your dirtbike though.

Most of the energy from combustion comes from oxygen, not the gasoline. The bigger the difference in temperature between the explosion and it's surroundings (the engine), the more energy you get out of the combustion. For this reason, cooler is better (obviously within reason).

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