what the hell (jetting)

[400exrules]

My 400 seems to run good, but sometimes when i run it hard, it will start to make a weird pinging noise. And i checked my main the other day, and the previous owner jetted with a 146 dynojet main for a slipon+filter :huh :eek2: . Doesnt that seem really low?
I havent done a real plug check, but when i changed it, it was dark (brownish black), like it was running rich. Should i raise the main and do a plug check? Whats the best way to do a plug check to get an accurate reading of how your jetting is?

[nosliw]

plug check it.

put in a new plug, and go out on a long straight trail ( or road ) slightly uphill if you can.

get up to speed fairly quickly, short-shifting it the whole way. WOT the entire time. when you get as fast as you can, kill the bike with the throttle still pushed in. get to a stop and let off the gas. check your plug.


that's how i do it. i get the same color of a brown paper grocery bag.

that's a run for the main, but you can do the same for needle settings, and hell, even pilot settings if you don't like finding your highest idle. just repeat, but instead substitute WOT for half, or none.

[JOEX]

I haven't used DJ's but from what i've read the 146 should be about right.

How's the fuel? If it's old or a low octane the motor will ping.

Also from what i've read the it is difficult to get an accurate plug reading with today's fuels, they have alot of additives. Go by how the motor is running or use an O2 sensor.

[400exrules]

well...the fuel is from like, november, but ive been riding it, so it hasnt just sat their. its 93 octane, i was going to drain it and put fresh fuel in but my dad called me retarted and said dont waste it....:rolleyes:

[JOEX]

Put the old gas in the car then buy new gas for the quad;)

[400exrules]

should i rinse the gas tank out too, or just replace the gas?

what would i feel if it was lean, would it sputter and choke at full throttle (mainjet)

[JOEX]

Draining and refilling might be 'good enough' but if it's the '99 in you sig cleaning out the petcock may be a good idea. I haven't got into that part yet so i'm not sure what's all involved.

There is a way to check at least one of the jetting circuits with the choke but I don't recall how at the moment. It's been mentioned how here several times though;)

[nosliw]

you mean just letting it idle, and slowly closing the choke? yea, if the rpm's start to raise then your pilot jet it soo lean. i suppose if you were quick enough you could slowly apply the choke while going WOT, but i don't recommend it unless your on a kfx/z400