blackmtx
Newbie
Is anybody having hot fuel problems with the Mtx? i was riding in Idaho in 35 Degree F temps and kept boiling the fuel in the tank....adding the jerry can of 3 gals would let me get the sled started again....problem came back every time the tank got down....i pulled the tank and checked the exhaust...no discoloration of the aluminum sheild or asbestos blankets....i did seal the header tighter where it goes through the bulkhead so i dont get straw and grass in the header/flex pipe area when riding in the fields at home....running a stage 1 supercharger at 7 pounds... the rest of the exhaust is under tunnel straight out the back....
Grimm
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Add some vents to the hood and side panels and install the OFT dash vent...get all that extra heat out from under the hood.
Imo, all OEMs are making the hoods too tight fitting and not allowing the engine, clutches and oil tank to breath. Getting more airflow helps cool under hood temps, making everything operate more efficiently.
Imo, all OEMs are making the hoods too tight fitting and not allowing the engine, clutches and oil tank to breath. Getting more airflow helps cool under hood temps, making everything operate more efficiently.
bholmlate
Expert
Grimm
Are you sure that you are boiling the fuel? I think there would be some discoloration in the compartment underneath the tank if header pipes were getting too hot. However I am not so sure that closing that area off is a good idea. I understand your concern about grass and straw. Also If your exhaust donuts are going bad i would think there would be some sign of that when you took the tank out and looked at the compartment under the tank.
The thing that came to my mind when you said that you put more gas and it would start back up was a fuel pickup problem in the pickup inside your tank If there is a crack in the fuel pickup once the level gets down to a that level you may be picking up air instead of fuel. Sort of like a cracked straw in a drink. it works fine when the drink is full but as soon as the level gets down below the crack in the straw you start to suck air instead of your drink.
I do agree with Grimm about not enough air flow under the hood but I really dont thnk venting the hood will solve your problems.
Are you sure that you are boiling the fuel? I think there would be some discoloration in the compartment underneath the tank if header pipes were getting too hot. However I am not so sure that closing that area off is a good idea. I understand your concern about grass and straw. Also If your exhaust donuts are going bad i would think there would be some sign of that when you took the tank out and looked at the compartment under the tank.
The thing that came to my mind when you said that you put more gas and it would start back up was a fuel pickup problem in the pickup inside your tank If there is a crack in the fuel pickup once the level gets down to a that level you may be picking up air instead of fuel. Sort of like a cracked straw in a drink. it works fine when the drink is full but as soon as the level gets down below the crack in the straw you start to suck air instead of your drink.
I do agree with Grimm about not enough air flow under the hood but I really dont thnk venting the hood will solve your problems.
MOUNTY
Expert
Grimm
Are you sure that you are boiling the fuel? I think there would be some discoloration in the compartment underneath the tank if header pipes were getting too hot. However I am not so sure that closing that area off is a good idea. I understand your concern about grass and straw. Also If your exhaust donuts are going bad i would think there would be some sign of that when you took the tank out and looked at the compartment under the tank.
The thing that came to my mind when you said that you put more gas and it would start back up was a fuel pickup problem in the pickup inside your tank If there is a crack in the fuel pickup once the level gets down to a that level you may be picking up air instead of fuel. Sort of like a cracked straw in a drink. it works fine when the drink is full but as soon as the level gets down below the crack in the straw you start to suck air instead of your drink.
I do agree with Grimm about not enough air flow under the hood but I really dont thnk venting the hood will solve your problems.
X2
Are you sure that you are boiling the fuel? I think there would be some discoloration in the compartment underneath the tank if header pipes were getting too hot. However I am not so sure that closing that area off is a good idea. I understand your concern about grass and straw. Also If your exhaust donuts are going bad i would think there would be some sign of that when you took the tank out and looked at the compartment under the tank.
The thing that came to my mind when you said that you put more gas and it would start back up was a fuel pickup problem in the pickup inside your tank If there is a crack in the fuel pickup once the level gets down to a that level you may be picking up air instead of fuel. Sort of like a cracked straw in a drink. it works fine when the drink is full but as soon as the level gets down below the crack in the straw you start to suck air instead of your drink.
I do agree with Grimm about not enough air flow under the hood but I really dont thnk venting the hood will solve your problems.
X2
meatman
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Boiling fuel
Hi, just a note, I had this issue on my grizzly 700. The electric vent for the Efi was malfunctioning. My dealer recognized the issue ( my bike was off warranty for three years ) and Yamaha had a service bulletin on the issue and all repairs were covered. Not saying it is the same but with a 1/2 tank and average use the tank would boil ( you could hear it ) and if you opened the tank cover you could see it boiling. But you could not run the bike with the cover off because the efi would just kill the motor. Maybe you have the same issue.
Good luck
Hi, just a note, I had this issue on my grizzly 700. The electric vent for the Efi was malfunctioning. My dealer recognized the issue ( my bike was off warranty for three years ) and Yamaha had a service bulletin on the issue and all repairs were covered. Not saying it is the same but with a 1/2 tank and average use the tank would boil ( you could hear it ) and if you opened the tank cover you could see it boiling. But you could not run the bike with the cover off because the efi would just kill the motor. Maybe you have the same issue.
Good luck
blackmtx
Newbie
Thanks for the input guys....i do have the Oft dash vent, works awesome....i did check the pick up in the tank,i have the external pump kit from Mpi and even replaced the pump last week with no improvement.....the fuel is definately boiling, i sat on the trail for half an hour at lower Mesa falls watching it bubble in the tank....using scratchers the engine temp stays at 170 till you shut the motor off then goes up over 210.....it seems like a heat soak problem, if i just play in the powder in never happens but i have to ride the trails to get there.... 
Grimm
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I've heard of this happening on some atvs as well.
Maybe you can try adding some more heat reflection tape to the tank.
Maybe you can try adding some more heat reflection tape to the tank.
Off Trail Mike
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Blackmtx:
Just a shot in the dark, but does your turbo fuel system return fuel to your tank? I know some turbo fuel injection systems do this and if you have an air leak in your system, it will appear like it is boiling.
My suggestion is to buy (their like $40 bucks) or borrow an infrared temperature gun and shoot the area around the tank and in the tank to see if you are in fact boiling.....cause if you are, I wouldn't be too keen on riding a sled with boiling gasoline.....all you would hear is ka....as in kaboom!
The boling point of gasoline varies widely 100-400F so if you are boiling at the higher temps, that plastic tank is going to get very weak, and you know the implications of this.
Good luck solving the problem.
OTM
Just a shot in the dark, but does your turbo fuel system return fuel to your tank? I know some turbo fuel injection systems do this and if you have an air leak in your system, it will appear like it is boiling.
My suggestion is to buy (their like $40 bucks) or borrow an infrared temperature gun and shoot the area around the tank and in the tank to see if you are in fact boiling.....cause if you are, I wouldn't be too keen on riding a sled with boiling gasoline.....all you would hear is ka....as in kaboom!
The boling point of gasoline varies widely 100-400F so if you are boiling at the higher temps, that plastic tank is going to get very weak, and you know the implications of this.
Good luck solving the problem.
OTM
meatman
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Fuel boiling
The reason I mentioned the fuel vent is that as pressure builds in the tank the fuel will boil at a much lower temperature. When this happens did you notice a pressure build up in the tank when you went to open it?
The reason I mentioned the fuel vent is that as pressure builds in the tank the fuel will boil at a much lower temperature. When this happens did you notice a pressure build up in the tank when you went to open it?
Off Trail Mike
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Re: Fuel boiling
Smart....meatman
It's got to be something like elevated pressure or vacuum in the tank happening, cause I can't see that much heat getting into a sloshing fuel tank and if it was, I sure wouldn't ride it with hot gasoline....
OTM
meatman said:
Smart....meatman
It's got to be something like elevated pressure or vacuum in the tank happening, cause I can't see that much heat getting into a sloshing fuel tank and if it was, I sure wouldn't ride it with hot gasoline....
OTM
APEX XPRESS
Extreme
blackmtx said:
This is part of of your problem
Yamaha addressed the straw issue by changing the header in 2010 and can cause also make fuel boil at high elevation and warmer temps.
Also running lean will increase temps.
I have seen this and also fixed the problem but you will get straw in the clam shell if you ride in the straw.
