There has been some discussion in the past about hard starting 400ex's. I just wanted to know if anyone has had any luck using any of the suggested fixes (or any new ones).

My 400ex will not start the next day (or week) after riding. I have to clean the plug- and then it will start but miss till it warms up. Most of the other 400ex owners I know have similiar starting problem, even though we all have different setups.

It seems to me the 400ex has a weak spark, therfore is very sensitive to fuel mixtures and clean plugs.

Jeff
00 400ex
87 Warrior

 

mine starts all the time any weather but my brother has the same year and he has problems staring his all the time. he always has to put a new plug in.

 

Stock 400s start hard because the factory jets lean to meet emisions standards (they note this in the owners manual), so they are very cold blooded. Once I richened mine up, starting was no problem. Never had any problems with plugs.

 

i have the same problem with mine i had to get a new plug or clean it after i have a day of hard riding......it sucks!

 

My buddy has a 02' 400ex he got last month. It's being stored at my house so I have started it many times. No matter if it's warm or cold outside I put it on full choke and hold half throttle. It turns over a couple times and always fires. Then slowly move the choke down. It actually says this in the book somewhere. We haven't had a problem with it since then.

 

A 45 pilot jet will do the trick. Mine fires right up even with the rev box on it.

 

change the pilot to a 42 or a 45 to get rid of the factory lean setting. If it is cold, the 400 will have a hard time starting with the vev box. The rev box is made for a kick start engine that spinns faster than your electric starter will spin the engine. There is a starting routine for every atv and motorcycle. If you don't learn that starting routine, you will not start the 400 very well. Maybe, that is why some people have to put plugs in every ride. My plug is over a year old. Also, what what kind of gas that you buy.

 

the best setup I have come up with is a 45 pilot jet and always, always use at least 93 octane