need help with my "new" 03 400 ex

[joe03400ex]

Hello all- I just purchased an 03 honda 400 ex and have not had much luck since I bought it. It came with a white brothers r4 slip on, k and n airfilter, not sure if its jetted or not-, skid plates and nerf bars- I'm going to jet it but not sure what jets to go with-, are there any "free" mods worth doing? I have already rebuilt the carrier, new chain and sprockets all oem. What type of maintenance should I keep up on besides air filter and oil changes? Previous owner said it sat for a year- it runs pretty good doesn't blow smoke but I hear the valves- is that normal? This is the first quad of my own and I would like to keep it in tip top shape all help would be greatly appreciated- I would also like to go a little faster without ruining its reliability. Thanks all hope to hear back soon!-joe

[hondaking52]

well first of all welcome. and wow you asked alot of stuff..,ur jet should be in the 140-150 range, or atleast mine was, i dont think anything in this world is free!, lol, as for maitenance, like you said change the oil, new spark plug wouldnt hurt, check everything out, see if any bearings are shot, as for the valves, the 400ex motor is a pretty loud motor, i would adjust ur valves just to rule that out tho, and as for speed, there's lots of things, hotcam, timing key(very cheap upgrade), bigger bores, change the tooth's on ur sprocket, well i hope i have answered a few of ur question's.

[rob_990]

i cant really tell you what jets you need.youll just have to see whats in there and go bigger or smaller from there.but if its not backfiring and its not bogging id lead it alone.

for free mods you can grind down your header welds,take the airbox lid off and remove your choke. but i think thats pretty much it. but if you do take your lid off you may have to rejet cause your quad will run a little leaner.

maintenance you can grease the aarms, front hubs, shock linkage, and swing arm bolt if yours isnt seized already.