Hey my name is Chris, and I am having issues with four-wheeler. Yes she is kinda old but kicks good! Untill now.... Anyways a couple of weeks ago I was riding with some friends on my four-wheeler and they were on my other 300. Then we decided to race, we were going good then I pushed my eiger 400 to full throttle and she started suptering and popping. (it did not die out) but after it did that, she quit moving Completely, and would not move anymore. Then I got pulledback to the shop, and left her there. Then the next day I went out there looked at her, didn't see nothing wrong. So I cranked her up. She would sit and idol jus fine. But as soon as I put a little bit of pressure on that throttle she dies out. I have tried sea foam and draining tank and new gas in it and still hasn't worked. I just don't know. Help anyone!?!??

 

you may need to clean out the carb or rebuild it and change the spark plug those would be a good place to start
i am new to 4 wheelers but have been working on vehicles my whole life also i just got me a 04' Eiger and love it it is doing the sputter thing until it gets warmed up think i am going to try the seafoam and if that doesnt help a rebuild of the car is in order good luck

 

Does it sputter with the choke on full? Try that since the carbs are assembled lean running to start with. I had the same issue and put a carb kit and also a dynojet which is a needle with notches and a bunch of main jets. Mine was set on third notch with a #126 jet (stock is 122) and the quad is running like the day it was new.
Do not discard the possibility of displaced magnets in flywheel, some early Eiger had that problem as well but start with carb first.

Good LUck

 

How long did yal race full throttle? Hope atv didnt float an value..Check compression to start with.. If engine been cranking an running great before raced,,IMO the carb wouldnt got clogged racing, But if you have been having issues with cranking or running before then yes this hard accel. could have broke something loose in carb, IMO then an carb cleaning an rebuild would be what needed, Do compression check get back with us here.