I went riding in hot weather (+85 degrees) and noticed fuel and vapor trying to exhaust through my Clarke Desert Tank overflow tube on my '06 FSE 450 after about a half hour. When I got back to the truck after an hour it was still happening so I pulled off the gas cap, which exhibited a bit of a vapor lock, and saw the gas boiling inside the tank. This continued for about 10 minutes so it must have been pretty hot. Anybody ever experienced this? Is it something to worry about?
Gas Gas Gas Boiling
- Thread starter reidnv
- Start date
iancp5
New member
I think I'd be quite worried about it 
It's pretty flammable at the best of times and if it's boiling it'll be giving off a lot of vapour - which is the bit that burns! There is also the fact that if it boils hard enough it is likely to blow the cap off and deposit hot, very flammable fuel all over your groin.
In other words you're sitting on a bomb.
You might want to check that there is nothing blocking airflow round the engine. Could be worth covering the underside of the tank with thermally reflective film. Also worth getting the Fi setup to ensure the engine is not running hotter (too lean) than necessary.
It's pretty flammable at the best of times and if it's boiling it'll be giving off a lot of vapour - which is the bit that burns! There is also the fact that if it boils hard enough it is likely to blow the cap off and deposit hot, very flammable fuel all over your groin.
In other words you're sitting on a bomb.
You might want to check that there is nothing blocking airflow round the engine. Could be worth covering the underside of the tank with thermally reflective film. Also worth getting the Fi setup to ensure the engine is not running hotter (too lean) than necessary.
That's kind of what I was thinking but I took it to a mechanic and he said it is quite common but most people just don't realize it is happening. Needless to say I was not satisfied with this anwer. It does seem to be running hot. Where do you go to get info or who can diagnose the the FI? I suspect this is the problem. The mechanic also mentioned that perhaps it was an issue with the fuel tank vent hose not allowing enough air into the tank to compensate for the fuel use.
I rode the past two weekends in cooler weather and the problem did not occur so it definitly is related to overheating.
I rode the past two weekends in cooler weather and the problem did not occur so it definitly is related to overheating.
Where you riding slow single track constantly without any faster sections giving it time to cool down. My 06 only brings on the fan (standard in Australia) when on slower rides but always settles down after some faster sections. They did increase the capacity of the radiators after the 06 though. Any more info??
It may very well be that I don't know what I'm talking about in this topic as I have never even taken the fuel pump out of my GGs tank, but I have seen fuel pumps that run hot enough to boil gas. It is possible for engine overheating to cause a problem, but the tank is plastic and in my unknowing opinion, if the engine was causing the problem, it would cause melting of the tank before it caused boiling of the gas inside the tank.
As was said above, your sitting right behind a boiling time bomb and if it was happening to me, I'd find a way to isolate the gas from the heat source.
Tony
As was said above, your sitting right behind a boiling time bomb and if it was happening to me, I'd find a way to isolate the gas from the heat source.
Tony
I would agree also.
I've see the new Husabergs do it and lots of KTMs.
Ethanol blended fuels seem to perculate quite easy.
Thanks for the replies. I was running alternatively fast and slow so that was not it. The gas was boiling hard around the fuel pump and my first thought was that for some reason air was coming out of the pump itself so the hot fuel pump may be the issue in conjunction with the gas. I got the gas originally from a Shell station so I will check the levels of ethanol there. Its probably a combination of stuff. Lastly how can I tell if the bike is running lean. Is there any way that does not require special tools or diagnostics.
Nick sold Cycle Pro and has dissappeared off the radar screen but I am trying to track him down. Last I heard he was in Reno.
Nick sold Cycle Pro and has dissappeared off the radar screen but I am trying to track him down. Last I heard he was in Reno.
iancp5
New member
When I got my 450 I kind of sensed it was running lean & there was more heat than my KTM. It just seemed to get up to temp too fast in winter. Took it to a dealer who confirmed it and trimmed the injection. Most of them are set lean from the factory to meet emissions but run better a when richer. I had a KTM before and neither boiled fuel even when in tough heavy mud when the engines were getting hot. Of course we rarely get temps over 90 deg F here even in summer. If it is down to having low boiling point products in the fuel I still wouldn't like it. Ethanol boils at 78 deg C which is still pretty hot. Another concern would be building pressure in the tank if you had vent block. If it is the fuel pump I'd still be worried and I'm convinced that's not normal. Maybe you should dip a guage in there when it's boiling to check the temp of fuel. Just don't make any sparks!!!! Fuel in the groin is unpleasant when it's cool let alone hot.
Another gas-boiling GasGas owner!
Went riding yesterday on my 05 450 FSE, and when taking a break, noticed that the vent tube was bubbling gas from inside of the tank.........thought that was pretty normal until I took the cap off, and was greeted by a literal guiser of hot gas spewing from the tank under a great deal of pressure!!!! I was shocked to say the least, and when I finished wiping the fuel off of my hands and jersey, I looked inside the tank, and the gas was just boiling, and bubbling all around the pump. I left the cap off for about 5 minutes, and the boiling very gradually subsided. What the hell???? It was only about 70 degrees out, and I was riding some tight, muddy, single track, but that shouldn't be happening should it? Does anyone have a cure for this? I'm also running a Clarke oversized tank by the way, and this bike has just 900 miles on the clock. To me, it shouldn't have anything to do with the engine being hot, or running lean........in fact mine runs damn good! It seems the fuel pump is just getting wat too hot, but why? 
Went riding yesterday on my 05 450 FSE, and when taking a break, noticed that the vent tube was bubbling gas from inside of the tank.........thought that was pretty normal until I took the cap off, and was greeted by a literal guiser of hot gas spewing from the tank under a great deal of pressure!!!! I was shocked to say the least, and when I finished wiping the fuel off of my hands and jersey, I looked inside the tank, and the gas was just boiling, and bubbling all around the pump. I left the cap off for about 5 minutes, and the boiling very gradually subsided. What the hell???? It was only about 70 degrees out, and I was riding some tight, muddy, single track, but that shouldn't be happening should it? Does anyone have a cure for this? I'm also running a Clarke oversized tank by the way, and this bike has just 900 miles on the clock. To me, it shouldn't have anything to do with the engine being hot, or running lean........in fact mine runs damn good! It seems the fuel pump is just getting wat too hot, but why?
In this case it was definately the pump, as you could see the gas was boiling just around the pump area, and not the rest of the tank. I read on another forum that it could be the fuel that I was using was purchased this past Spring, and it may have been "winter gas" which for some reason boils easier than "Summer" gas? At any rate, I'm going to keep a close eye on it from now on!
