wont start. ran great two weeks later wont start

[jasonwayne222]

well just got done rebuilding all mods listed below. build went good bike runs great has a lot of power. well i went to work for two weeks and was gone. got back last night, i started it and let it idle for a few seconds and killed it cause it was late.

Now today i cant get it to start for the life of me. It will pop every now and then but i cant get it to start. I know I got spark and fuel. so what the heck is goin on. Something with the jet kit or the way i set the a/f screw. its about 10 to 15 degrees cooler then it was when i built it a couple weeks ago.

[jasonwayne222]

tomorrow im gonna check the valve clearance

[fastredrider44]

400EX's are not known for their cold cranking ability. I'm not saying that its too cold outside to start, but the 400s are picky. Since you let it sit, what kind of gas are you running? I know you said you just cranked it the night before, but that could have just been a little gas that was already in the carb. That Ethanol crap that they put in gas is a killer on carbs. I'd start with cleaning the carb even if it looks clean, to make sure it's getting fuel into the cylinder.

[b.lee]

Originally posted by jasonwayne222
got back last night, i started it and let it idle for a few seconds and killed it cause it was late.


Everytime you start it, you should always ride it or let it warm up fully... if you do not you run the risk of fouling your sparkplug

Might need a new one.

Or if it was indeed very cold out, they are a bear to start in the cold temps. I would try putting a ready heater next to it to warm up the engine cases (not too close)

After it warms up it should start fine... or its the plug most likely

[jasonwayne222]

i live in louisiana so it wasnt that cold, just finally cooled off a bit, its only70 right now. And I pulled the plug and cleaned it and still the same thing. possibly the pilot circuit on the carb is clogged. I run premium gas with 104 octane booster

[jasonwayne222]

ok well worked on it today. cleaned carb, but it was good, put new plug made sure it was sparking, checked valve clearance and they had way too much clearance, adjusted them, still wasnt the problem, ended up being a blown head gasket, when i put it back together i used the old one, not good, so im gonna put a new gasket on it and be done with it, it just didnt have enough compression i guess

[fastredrider44]

Make sure to use a torque wrench and do it in stages and cross tighten the studs. Final tighten should be 28ft lbs. This will put your mind at ease if you suspect any head studs pulling.

[jasonwayne222]

Just curious where did you get your information about that torque spec? According to my manual and every other persons the torque is 33ftlbs. and i know how to torque im a helicopter mechanic