Posts
2006
Joined
11/9/2011
Location
Denver Metro, CO
US
Rider 5280
6/10/2022 11:59pm
6/10/2022 11:59pm
Edited Date/Time
6/13/2022 11:25pm
Guys - I ran into something I've never encountered before today.
I was running my carbureted 2008 Honda CRF450R at an elevation of ~ 8500-ft (and it was ~ 90 degrees F out) on Colorado mountain trails and the bike started to run weird/fuel-starved like, so I pulled over, removed the gas cap, experienced a major pressure release, and then when looking down into the tank, the gas appeared to be boiling. Literally ... a rolling boil like this:
https://www.youtube.com/watch?v=0c1aeLm-Z7o&t=34s
I checked my gas cap's venting system (I use a check valve vent) and it was still breathing OK on vacuum. The engine coolant wasn't particularly hot at ~ 175-200 degrees F. Lastly, I was running 91 octane pump fuel with Yamalube Fuel Med Rx additive to combat ethanol issues.
I haven't dug into this yet, but it was the oddest thing.
Has anyone here seen this before and if so, what was your fix ultimately?
*** I can upload a video of the actual event later this weekend if that helps anyone diagnose this ***
I was running my carbureted 2008 Honda CRF450R at an elevation of ~ 8500-ft (and it was ~ 90 degrees F out) on Colorado mountain trails and the bike started to run weird/fuel-starved like, so I pulled over, removed the gas cap, experienced a major pressure release, and then when looking down into the tank, the gas appeared to be boiling. Literally ... a rolling boil like this:
https://www.youtube.com/watch?v=0c1aeLm-Z7o&t=34s
I checked my gas cap's venting system (I use a check valve vent) and it was still breathing OK on vacuum. The engine coolant wasn't particularly hot at ~ 175-200 degrees F. Lastly, I was running 91 octane pump fuel with Yamalube Fuel Med Rx additive to combat ethanol issues.
I haven't dug into this yet, but it was the oddest thing.
Has anyone here seen this before and if so, what was your fix ultimately?
*** I can upload a video of the actual event later this weekend if that helps anyone diagnose this ***
Ethanol boils at sea level at 173f and about 160f at 10k feet. So maybe start with a non ethanol fuel and see if that helps.
Water boils at about 190f at 10k feet for reference.
In a vented container it would just cool itself by evaporation though, and not actually boil. The boiling comes from being warm under pressure and then the pressure being released.
So what kind of check valve are you using on your vent hose? It's supposed to allow some pressure venting but it closed, but I've heard even the OEM ball valves can have the same problem.
I recall years ago having a similar but different problem with a check valve add-on, so I think I am just done with these devices.
Thanks guys - you gave me some great advice!
Do you think I damaged my fuel tank and now it's potentially unsafe to run?
I rode it like this for 5 hours on/off. Was kinda stuck in the "way back" trails as I made my way out after realizing what was happening.
The Shop
Back on topic, rode the 450, boiled the fuel, had a great time.
Post a reply to: Um ... fuel boiling in the gas tank?!