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arcboy

questions about the 07 YZ450

12 posts in this topic

Ok so I have had a 400 and 426 and naturally I moved into a 450. They are all awesome but got some questions about the 07 YZ450 and that the bike has if its lucky 10 hours on it. All stock and SUPER clean!!!!!

1. After reading they seem to run hot but I don’t remember any except this one loosing coolant out of the overflow.

2. So after riding about half a tank worth I noticed that it started to bog really bad, so I thought it was out of gas. I opened the tank and a huge hiss and a volcano of gas vapor poured out. I checked the vent tube and it is venting easily because I can blow though it and I can instantly hear the vapor venting as soon as I put it back on. Pretty sure that I shouldn’t have take the cap off after an hour or two ride or riding.

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This sounds identical to mine when it overheated on a very slow ride. I turned it off and heard the hissing, thought it was the coolant coming out and it was in fact the gas air hose making the sound... Opened up the lid and hear a pssshh and the pressure got released

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My 04 did the same thing till I got rid of the fancy little vent the previous owner put on it . I went back the the plain old vent hose or tube. I found that although the stubby vent worked it just did not vent fast enoughthen the pressure built up and forced gas in past the float valve and started to bog the bike. I made a long vent tube that went behind the # plate then dumped out with the rest of the vents right in front of the rear tire. I'm glad I had it that long when one of my buds ran out of gas. It made a great siphon hose.

Edited by allterra

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That's why I remove the small Yamaha vent thing-a-ma-jig in the gas cap hose. It's there to allow air to enter into the gas tank, and to stop fuel from flowing out if the bike falls over. But in my case, in the slow technical terrain, the engine heat pressurizes the fuel in the tank since the one way vent won't allow vapors to leave the tank. Instead, fuel is pushed into the carb, creating a seriously rich carburation issue, which sometimes floods the engine out. Removed, no issues.

Maniac

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Great... another mod to do, (at least its free) I never had a vent thingy before so I wondered about it..

Also while we are talking about overheating, who uses a high pressure rad cap (assume just switch with a YZ part)? It seems mine starts puking coolant very easily and was wondering what folks were doing in hot summer tight woods riding as I would think this would be an issue... discuss

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Great... another mod to do, (at least its free) I never had a vent thingy before so I wondered about it..

Also while we are talking about overheating, who uses a high pressure rad cap (assume just switch with a YZ part)? It seems mine starts puking coolant very easily and was wondering what folks were doing in hot summer tight woods riding as I would think this would be an issue... discuss

The way I see it if I ride at like 5mph or idle for too long it will overheat, If I can keep it at like 20 in gear 2 it will never overheat .

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Ok so I have had a 400 and 426 and naturally I moved into a 450. They are all awesome but got some questions about the 07 YZ450 and that the bike has if its lucky 10 hours on it. All stock and SUPER clean!!!!!

1. After reading they seem to run hot but I don’t remember any except this one loosing coolant out of the overflow.

2. So after riding about half a tank worth I noticed that it started to bog really bad, so I thought it was out of gas. I opened the tank and a huge hiss and a volcano of gas vapor poured out. I checked the vent tube and it is venting easily because I can blow though it and I can instantly hear the vapor venting as soon as I put it back on. Pretty sure that I shouldn’t have take the cap off after an hour or two ride or riding.

Was feeling bad about kinda hi-jackig your post.

I'll add my two cents worth to make up for it.. Haha, First you say its a YZ so I assume you don't mean a WR but the only differance is the puke tank on the WR and a lower pressure rad cap..

That sounds mighty hot reguardless but you didnt mention if you were on a moto track or off road.. But either way here is my overheating checklist in order of what I would check

1: obstruction in the radiators, ie; mud, dirt, stray dogs... Anything not allowing air to flow through, even some of the aftermarket guards can restrict flow quite a bit.

2: working water pump, make sure someone didn't screw up a water seal replacement and bike isn't circulating coolant correctly.

3: correct coolant, I'm a fan of using coolant for motorcycle engines. It is lower viscoity and therefore circulates easier in the system. I also add redline waterwetter (available at autozone) to help aid in cooling

4: check cap, could have a faulty cap that isn't holding pressure.

5: pluged up radiator or coolant passage, someone could have added stuff trying to patch a leak... and have system blocked, should be easy enough to see any stuff floating in coolant.

6: jetting, if jetting is super lean she will run hot.

Reguardless I would flush cooling system and replace coolant but there is probably something else leading to the overheating.

And as far as my thoughts on low pressure cap... 20mph is impossible to do in AA sections of trail and not to mention bottlenecks in AA sections where I'm lucky to avg 10-18 mph. All bikes overheat especally four strokes but I want to try and be as good as possible at keeping juice in my radaitors. So my thought is to increase system pressure via a high pressure cap to raise the boling point and keep the puke tank, just wondering if anyone is doing this with succes or is it a waste of time..

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Ok. Those are some things to check out.

I don't like how the vapors leak out so easily and I'm pretty sure it is stock YZ breather tube. I dont really want to replace it with a plain hose but I might have to. I guess I'll keep it rubber side down. Just wondering if anyone else had this problem.

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Rocky, Don't worry about Stealth's 20mph comment. He's Canadian! He doesn't even know how fast 20mph's is!!! Just bustin' your chop's Stealth!!! Maniac

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Rocky, Don't worry about Stealth's 20mph comment. He's Canadian! He doesn't even know how fast 20mph's is!!! Just bustin' your chop's Stealth!!! Maniac

I'd say about 33kmh. I do lots of trails at like 30-50 here

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I use straight 5 year dexcool. While some will say it runs hotter, most that have tried it stick with it. Using it in both the supermoto street wr450 and the dirt one. They seem to do better when they are not puking out their fluids.

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