I just upgraded from an 03 280 Pro to an 07 300 Pro. I'm riding in the same area, doing the same climbs, etc, and have been having problems with the 300 stalling out on long climbs where the 280 had no problems. It seems to be heat related - the last time it happened, I simply opened the gas tank, venting the pressure, and it fired back up. The vent hose is not blocked. I'm using the same pre-mix at the same ratio - 70:1. It seems as though I'm boiling the gas. Is this common? Does the 300 run hotter than my old 280? Am I running too lean? Any ideas would be appreciated. Thanks,

Forrest

Check the fuel line and see if its close to the exhaust pipe if so reroute it. The Fantic 305 did this a lot, people made heat shields to keep heat off the fuel line.

No mine does not have this problem you have. I would check all the overflow pipes on the carb make sure none are blocked.

I'm on my third 300 pro now and have never had this problem. I have heard the petrol/gas boiling in the tank after long fast road or moor runs but never has it caused a problem.

Check the flow from the petrol tap, Ive heard that some times the gasket get miss aligned. And check the filter in the carb, and the float hieght.

Ian

I guess it will be the inline one way valve on the tank breather, I've seen loads of bikes do this.

The ball inside them gets forced closed somehow then the tank pressurises due to the heat and your bike runs rubbish as it's getting force feed fuel.

Either remove the one way valve or drill a tiny hole in the plastic ball to stop it sealing closed.

Thanks for the replies. I do need to go back through the carb and make sure I don't have any of the issues mentioned. I did just go and check the cap again, and I can tell that sometimes the valve is closed, sometimes open, and it seems that when it is closed, it is not letting air out. Which way is supposed to be the "one way" - in or out? I just poked a piece of safety wire through the hole, and now it seems to be open in both directions. Would I need to disassemble the cap to drill any holes or remove the valve, or can I just run a tiny drill bit through the vent hole?

Thanks again for all the suggestions.

Forrest