Fuel boils in fuel line

[Lars]

I rode on the highway yesterday when the engine stalled because of lack of fuel. I knew something was wrong because I had filled up 15 km's before. So I look at the fuel line (mine is transparent) and I notice the gasoline is boiling  

We have a heatwave going on here and everything got so hot I almost couldn't touch the fuel petcock.  Because of the length of fuel line between tank and carbs it gets plenty of time to warm up. In my bike even more because I mounted a big Honda fuel filter wich sits behind the cylinders under the carbs.  

Are there others who have experienced this? What's  the best way to solve this? Is there heat-shielding stuff that I can use on the fuel lines/filter, or should I change the entire system so that the length of fuel line is reduced?


grtz,
Lars

[glenn9171]

Can you cut the lines to reduce their length?  Wouldn't the heat necessary to boil gasoline melt the transparent lines?  Check any local auto parts stores for fiberglass exhaust wrap material.  Wrap lines and fuel filter with this and secure it with wire ties.

[Lars]

Before I used it, I tested the transparent line for melting. Even at  this temp. it's far from the point it starts melting. Also, fuel starts to boil at lower temps than water.  

I can't make the lines shorter without altering the entire fuel system. the glassfiber exhaust wrap may be a good idea though, but it 'll look really ugly  

*not that that's a big problem on a bike with duct-taped turn signals.  :mrgreen:

[Pkaaso]

Lars, is your bike running hot.  I mean have you jetted the carbs to keep the engine from running too lean? What do your plugs look like?  They should be a nice tan color. If they are real light tan or white, you need to richen up the fuel mix.

I have a hard time believing the ambient temp could boil the fuel.  Maybe if it where standing still in the lines but it is moving.  Sounds like your engine is getting too hot and causing the fuel line to absorb too much heat.

I'd like to hear more about this.

Paul

[Lars]

It's jetted correctly with #125 jets and #40 pilots, needle 1 notch higher. However, when it starts boiling, the engine will get less fuel, thus running leaner,thus heating up the engine more.

I think it started boiling because of the extreme ambient temp. (45-50 degrees celsius or so in the sun)  and the fact that I have a big fuel filter. The flow in the filter isn't high; it acts as a reservoir wich gives the fuel a chance to heat up. The lines from the tank to the petcock are squeezed between the airbox and the frame. I almost couldn't touch the frame and the petcock because of the heat.

So normally there is no problem, only in these extreme circumstances. A Gs with standard fuel system would be less affected because it has no fuel filter.

The best solution would probably be a different fuel system with less and shorter hoses. The problem is that there isn't room for a petcock to be mounted. So the option is: a petcock mounted under the tank (would this be reachable without unmounting the tank?) or no petcock at all. I'm not going for the last option because when the float needles start to leak, huge amounts of fuel could leak away.

Maybe it's not a bad idea to look into soluton nr1. A lot of problems I had with the bike are attributed to the fuel system. (rust in carbs, air in filter, not enough flow)

[Rema1000]

I rode on the highway yesterday when the engine stalled because of lack of fuel. I knew something was wrong because I had filled up 15 km's before. So I look at the fuel line (mine is transparent) and I notice the gasoline is boiling  

Are there others who have experienced this?

Sounds a bit like my problem last night http://www.gstwins.com/forum/viewtopic.php?p=30633: hot day, bike had been parked in the sun.  On the freeway, it acted like it was out of gas (only 62 miles since fill-up).  I pulled-off and waited, played with the petcock, and it finally started on PRI.

JeffD "the secret moderator" had a similar problem to yours //ww.gstwins.com/forum/viewtopic.php?t=756.  He had a clear filter and could see bubbles in the filter when he revved it.  
I don't have clear fuel hoses or filter, so don't know what mine looked like.