A friend of mine has a 08 Rancher 420 ES, the problem he has is when at cold start the bike fuel system works fine and bike works fine but when his 420 reaches operating temperature and you punch or WOT the gas it bogs bad and no power at all. Now the strange thing is one of my friend blew in the vent hose for the Fuel Cap gas while I was WOT on the gas lever and the bike started running fine again. So that makes me think that when the bike gets to operating temp the fuel pump does not supplies enough fuel or pressure when you WOT but when you blow on the vent hose on fuel cap the bike runs perfect. any ideas on this?????? It really threw me off that blowing on the gas cap vent line made the 420 run better again while WOT but doesn't make any since to me why it works perfect at cold start and engine bogs at operating temp???? Also not sure about this but like on cars can that gas cap not be holding pressure and releasing all pressure out????

 

Shouldn't be a pressure issue as the tank is not under any pressure due to the vent hose. I would start by checking the petcock and draining the fuel tank. It could be you have a pinhole leak in the rubber intake going to the carb. While I was at it I would go ahead and remove the carb for a good cleaning.

 

08 Rancher 420 Is Elec Fuel Injected No carb. Thanks though!

 

While i was at it I would try running it with the vent hose off the cap, it could be pinching itself shut when you route it thru the dash.

Shouldn't be a pressure issue as the tank is not under any pressure due to the vent hose. I would start by checking the petcock and draining the fuel tank. It could be you have a pinhole leak in the rubber intake going to the carb. While I was at it I would go ahead and remove the carb for a good cleaning.</end quote></div>

 

Wasn't sure if it was EFI or not. That sounds like either fuel pump or weak injector.

 

Wish I had the bike at my house to tare it down and find out. I also thought about the Fuel pump and injector but doesn't make sense why it works fine at cold start but bogs at operating temp? When you blow on the vent line it runs fine. All I can think is the fuel pump and injector for now.

 

Not sure about the operating temp, but it sure sounds like the fuel pump. If it is weak you putting presure in the tank it is forcing more fuel thru the pump. Keep me posted on this one.

 

I will.

 

Someone at highlifter.com recommended me to do this, wont hurt to try it.

 

Sounds good. Won't hurt to give it a try. At least we are on the right track with the fuel pump.