We just moved from 7000 foot elevation to 1400 foot elevation. The bike started just fine when we got here so I could get it off the trailer. It sat over night and now it wont start. It turns over but will not start, just a loud backfire. Any idea what this might be?

 

welcome to the forums dude......more info on the bike might have rendered a quicker response. i'd like to assume that the bike has a carb and not efi? if so, you need to rejet, if it's efi you need to remap the ecm.

 

+1
It's a known fact that as you go up in elevation the less oxygen there is. The correct amount of oxygen is required to be present for proper engine operation. A carbed biked tuned for sea level will actually run too rich at high altitude simply because there are not enough oxygen molecules present to correctly light off the mixture.*
So, in the thinner air (high altitude) is the amount of fuel that is flowed into the carbs becomes too much for the lack of air (oxygen) present. The mix becomes too rich with fuel and the engine becomes sluggish and will not perform. *Visa versa in low altitude air is thicker and mix is too lean.*

Easy fix if carb, just rejet. ECM tune if efi.*

 

I have a question. If this issue occurs going from high to low altitude and vice vest, how can you ride across various states without having a problem? I know dumb question but just have to ask. Thanks

 

I'm thinking that they are thinking: Since the bike was hauled and not riden, then the ECM didn't get to learn the new air mixture. While riding, the ecm will be making adjustments for the new higher or lower oxygen amounts.

 

We need more info to help. What year and model is the bike? Have you had any modifications done?

 

I don't know what year your bike is, but I agree with the above solution, I have had this happen with both carb and efi bikes when going from one altitude to another.