Elevation Change Backfire

Ijust purchased a 2000 wr 400 a few months ago,prev. owner road mostly

in the woods at higher elevation.

Iwent to a race in the desert at lower elevation this weekend and the bike was backfireing at most hard shifts under acell.

I know i need to change the jetting,however i don't know how to tell what

size is in the bike now. If I take the jet out will the counterman at the local

dealer be able to teel me what size it is? If so what direction do i need to go?

I will be riding in higher elevations later this season,but i don't want to damage the carb or engine by running the wrong jet size when i ride desert.

Some of our rides will start on desert floor and ride to the tree line

is there a size that could work for both? :banghead:

I'm sure this subject has been posted before but any help would be great


The size is stamped on the jet...SC

At higher elevations or warmer temps than the atmospheric conditions for which the bike is properly jetted, you should need to lean it out.

FYI--you mentioned "jet" and not jets--there are a few in the carb plus the needle. So, you may have the swap out more than 1 jet and/or adjust the needle clip position.

Read through the Jetting Database at the top of the forum.

Elevation does effect jetting. Depending on how "high" you climb depends on whether or not you jetting should change.


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