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I know alot of people are having alot of problems with "boiling fuel" issue I too have had the same problems. I have done alot of research on this, because this problem just aint right. I have talked to alot of different people and have got alot of different answers, but this is what I have learned. I talked to a yamaha tech and he told me that the problem is that the fuel is actually boiling. He blames it on the "winter" fuel, he says that winter fuel has alot lower boiling point than summer fuel especially under pressure. pressure building in the tank is the second problem, the only advice he could give me was to try another brand of fuel, but all fuels in my are are winter fuels until about the 1st of June. He said that explosion wasnt gonna happen, but on mine it was building up so much pressure that it was blowing fuel out the vent hose "alot" and my thinking is that if it runs down on the pipe that could cause a fire. I talked to a good friend of mine at a local dealership here in town and he was very familiar with this problem, he told me the only fix until summer gas is availible is to use a fuel additive Blendzall octane boost/racing castor or mix 1/2 racing fuel and 1/2 regular pump fuel, and also to drill the vent holes in the stock fuel cap so the tank could vent better. Buying aftermarket fuel caps will not help. I started running 93 octane pump fuel with the Blendzall additive and drilled my gas cap vent holes and I havent had any more problems. The reason the fuel light comes on when you know that you have a almost full tank of gas is because when the fuel is boiling it is bubbling and causing it too vaporize and the fuel gauge cant read the level correctly. They are having this same problems on the new efi Harleys..

In my opinion this is a serious issue that Yamaha should address, but they just aint. They are aware of this issue, but my problem is that summer fuel is only avaible in my area 4 months out of a year. My suggestion is that all of you guys having this problem call Yamaha and raise a little hell until they address this issue.

Also check to make sure that you the updated fuel pump, I know on the early 06' models they had a faulty fuel pump. Having the faulty fuel pump can also cause over pressure in the tank.

Anyway, just throwing in my 2 cents. Hope this helps.
 

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I'm a bike guy and have had this problem on a Honda CR450F, YZ450F, and also a KTM525. The fourstrokes of today run quite hot and this seems to be a pretty common issue across the board.
I race and depend on my bikes to run excellent at all times. The way I fixed this problem was to buy Heat Tape and line the underside of my tank with it. Change out your coolant and replace with Water +Water-Wetter or Purple Ice. This cured my boiling problems on three different brand bikes. You raptor guys may have a little different setup as far as engine clearance etc...however it never hurts to try what I suggested.
 

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Bikeless said:
I'm a bike guy and have had this problem on a Honda CR450F, YZ450F, and also a KTM525. The fourstrokes of today run quite hot and this seems to be a pretty common issue across the board.
I race and depend on my bikes to run excellent at all times. The way I fixed this problem was to buy Heat Tape and line the underside of my tank with it. Change out your coolant and replace with Water +Water-Wetter or Purple Ice. This cured my boiling problems on three different brand bikes. You raptor guys may have a little different setup as far as engine clearance etc...however it never hurts to try what I suggested.
i agree it cant hurt at all,but it shouldnt be happening.. but i will give it a shot at this point.
 
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