HELP kfx400 not running

[kfx400isdashiz]

ok i ate the tranny on my 03 400 so i got a new bottom end. i switched the top end over. used a drz e base gasget. stock cams and pistons and now it doesnt run. it blows the sucks jsut a lil the blows again out the exhaust. anyone know whats up

[GPracer2500]

Could be the cam timing isn't set correctly.

Is there spark?
Is the carb delivering fuel?
Have you checked the compression?

[kfx400isdashiz]

i was thinking cam timing, but how do i check that? it has spark, you can smell fuel out the exhaust. but is it normal for it to suck in a lil bit on the exhaust.?

[GPracer2500]

The exhaust valves do open a little bit Before Bottom Dead Center. But I don't think that would create much if any noticable suction through the exhaust. Sounds like the timing is off.

A service manual will tell you exactly how to set the cam timing and I would highly recommend that you get one. But there are going to be some marks on the outside face of each cam sprocket. With the piston at Top Dead Center those marks will align with some reference point on the head.

Here's a couple pictures. Notice the arrows on the cam sprockets? They should be aligned as shown in the pictures with the piston at TDC on the compression stroke.

http://www.mxsquid.com/images/camtiming.jpg

http://img208.imageshack.us/img208/2990/picture18ti.png

[GPracer2500]

Here's a pic of the "T" line that marks TDC as seen through the inspection hole. Remember that there are two TDCs--compression and exhaust. So if your cams don't look right with the TDC mark lined up then spin it around another time.

http://img54.imageshack.us/img54/1363/cimg1423resizejf5.jpg

[kfx400isdashiz]

thanks man i think that will help alot

[kfx400isdashiz]

ok i didnt touch the cams, and i got it running. it idles high and no matter what i do with the adjustment on the carb it wont go down. it also will shoot flames out the exhaust and back fire. i do need to rejet because of a new exhaust. so any tips on that would be good. and i am curious what reasons its idling so high

[kfx400isdashiz]

does cam timing have any affect on the idle?

[GPracer2500]

Excess heat, erratic idle, shooting flames, and backfiring are likely because the jetting is too lean with the addition of exhaust mods. Rejet (don't forget about the pilot circuit) and I bet those problems go away.

Also make sure there are no air leaks between the carb and the engine. A good way to check for leaks is to spray starting fluid (or almost any flamable liquid) around all the joints and listen for a change in idle speed. If it changes when you spray on a particular spot than that identifies a leak at that location.

[kfx400isdashiz]

ok thanks ill put in bigger jets, anther question, i kinda liek the flames otu the back is ther a way to get this and have your quad run right. its an lrd slip on . it sooms to be jsut a straight pipe


so yo uthink jsut a main jet and ill be alright

[GPracer2500]

Originally posted by kfx400isdashiz
ok thanks ill put in bigger jets, anther question, i kinda liek the flames otu the back is ther a way to get this and have your quad run right. its an lrd slip on . it sooms to be jsut a straight pipe


so yo uthink jsut a main jet and ill be alright

Flames are generally an indication that irregular combustion is taking place (because of being too rich or too lean). I'm not aware of a practical way to create flames with a correct air/fuel mixture. Sometimes I'll see certain (professional) road race bikes shoot orange flames on decel. I think that happens from engineers purposely setting the FI systems to go rich on a closed throttle for cooling purposes. Don't try it on your carbureted ATV engine.

If the fuel screw provides enough adjustment to get the pilot circuit correct than a main jet change may be all you need. But you may have to change the pilot jet to get the pilot circuit correct. There's a "How To" in that section detailing the procedure for setting the fuel screw and confirming that the pilot jet is the correct size.