spark plug question

[cant400exbeatit]

i just got an HMF slip-on for my 400, and i'm gonna jet it this weekend. if i'm going to check the spark plug condition to determine if it's running lean or rich, how long should i run my quad so i get an accurate reading on the spark plug.

also, what size main jet do you guys suggest, only performance mod's are the pipe. i am going to run it with the airbox lid on also. thanks.

[RideRed250ex]

If you want to make a main jet check you need to get a new spark plug. Put it in somewhere where you have plenty of room to ride. Get on it, ride it pinned full throttle to top speed keep it at top speed for a minute or so. Pull in clutch and kill the motor. Kill it while its still pinned and not while the revs are goin down. Stop, take out the plug, if it is wet main jet is to big, Brownish color or something like that it is the right main jet, if its a peachy color main jet is too small. Like I said thats only for the main jet. there are different ways to determine the clip and piolet jet. If you do a search you should be able to find it. I don't know what size is normal for the 400, but i would recomend that you get a aftermarket filter with your pipe and removed lid. K&N or UNI are prolly the best. Just to get a lil more performance outta the pipe and rejetting. Hope this helps.
Anyone else if you see something that needs to be corrected feel free! Otherwise i'm pretty sure this is how it is done.

[cant400exbeatit]

thanx for the info!..........anyone have any other ways of doing this??

[cals400ex]

i would start around a keihin 152 mainjet.

[nosliw]

i did mine like mentioned but i short-shifted the **** out of it up a very slight grade to put a load on the engine. heard it was the right way to do it. cant complain it worked and i'm running a 152