Need Help and Advice Please!!

[02Ignite]

I recently bought an 02 400ex, and has the following mods: different cam, different piston, K&N airfilter, different jets, HMF slip on exhaust! My issue is i want it to go faster, but first i have to get it running right! When i got it, it ran awesome the first weekend i got it. I took it out about a week later and it started missing bad and then would kill! Now the more i play with it, it seems like its only when it gets hot(it misses real bad then kills)! I had the coil checked and also swaped the CDI box with one off another 400 and still does it! I'm at a loss! Please help before i bring it to a shop and dump money into diagnostic fees!!

[REPOMAN]

what does your spark plug look like? also what cam and piston does it have exactly?

[the Z Man]

probly have crap in the carb. valves outta adjustment...

[02Ignite]

I will have to look and see i forgot what cam and piston it has, and i need to take and clean the carb out! But it just seemed like it would be electrical if it only didnt when it was hot! If it was junk in the carb or jets wouldnt you think it would run like krap from the second you start it?

[the Z Man]

Sometimes it take a minute for the crap to block the jets, one little tiny piece can screw it up..

[Pipeless416]

you said it has a different piston.. do you know what the compression ratio is? is it possible that it requires a higher octane fuel, and thats what it had when you got it?

[02Ignite]

It does, it requires 93 and thats what i have been putting in it! I'm going to drain the tank and refill it with shell gas, b/c it may be possible theres trash in there to and i'm going to clean the carb out and go from there! will keep posted! And any other suggestions keep them coming thanks! (and where is the fuel filter on these bikes b/c i'm going to change that to!

[Pipeless416]

Originally posted by 02Ignite
It does, it requires 93 and thats what i have been putting in it! I'm going to drain the tank and refill it with shell gas, b/c it may be possible theres trash in there to and i'm going to clean the carb out and go from there! will keep posted! And any other suggestions keep them coming thanks! (and where is the fuel filter on these bikes b/c i'm going to change that to!

actually there is not a fuel filter, but installing an inline filter would be wise.

[02Ignite]

I'm going to clean the carb and drain the gas tom.(monday) and pray to god that she runs right! After its running right would the Curtis Spark timing advance key be a good idea! Was also thinking of a 450 carb?

[nevadanotch]

When you clean the carb you may want to strip it down and soak the non plastic parts in a carb cleaner like Berryman. One you have done the soak you will want to blow all of the passages out with compressed air or use an aerosol carb cleaner to clear all of the passages.

Remember all it takes is a little dirt into the tank to really clog up a carb!


As far as the timing mods you will need to know what mods have already been done to the motor before using a timing key. A timing change will make your motor run hotter. You may not want or need the timing change!

Good luck!

[02Ignite]

Yea, i was reading about the timing key and said to use with stock piston! So for right now i'm going to focuss on getting the thing running right, so i can drive the thing! It kills me when my buddies are out riding and i got a broke down bike and a trx90 lmao sitting in my backyard! Will post tom afternoon after i run it!

[BigBore24]

make sure the float in the carb didnt stick causing it to overfuel and possibly get fuel into your crankcase. had that happen to me and it did the same as far as getting worse when it was warm

[02Ignite]

Didnt get a chance to test it out today, and i got school all day and night tom so i'll have to do it wed. And to be more specific it has a wiseco 11.1:1 piston w/stage 2 hotcam!