400ex wont start

[whitt304]

Here is the background info. My 400ex was smoking like mad and blowing oil out the exhaust, but it ran fine, so I figured I would do new piston and rings in it and have it bored out a bit while doing so. So I had it bored 40 thousandths and put it back together only to have it not start. It would pop every couple revolutions or so but never start. I found I messed up when grinding the rings to fit, too much gap, so I figured it must not have enough compression. So then I decided what the heck why not get a 440 big bore kit for it, solve the problem right? wrong. Still wont start. it does pop more frequently but still no start. I checked the timing, it is good. Any ideas? Hope someone can help me. Thanks.

[JOHNDOE83]

If you pore gas into the carb and it still doesnt start, try a new cdi.

If the gas trick makes it work for a sec, then turn the pilot screw out more and try again, make sure your gas is on and get new gas if you dont have it.

[PaRedneckRiders]

Just a though, try a new spark plug mine is doing the same thing to an extent. I have checked multiple things and i have not tried a new plug yet but im going to try one tomorrow and see how it works.
0

[whitt304]

Thanks for the suggestions, I'll give them a shot tomorrow and let you know how it turns out.

[CJM]

You did try and rejet it right?

Gotta verify:
1. Its getting gas, drain the float bowl after trying to start it, it should POUR out gas, no gas means its clogged somewhere. Clean the carb and check the lines as well as the floats and jets

2. Spark: Take the plug out, put plug next to something metal and crank-should get a spark. No spark try another plug, still no spark your cdi be bad.

3. Air: Try removing the lid, putting the lid back in, remove the filter, put your hand over it and try and crank it.

Also when you put it back together you did A. Time it properly, B. Adjust/check the valves, C. The cam went in with the lobes facing DOWN, D. If stock cam the decompressor is on it and working or maybe remove it and see.

[whitt304]

I think I found the problem, the cam setting plunger is missing, so I got one ordered and will have it Wednesday afternoon, So I will get back then to say if it worked or not. I hope it does.

[whitt304]

Well it was the cam setting plunger piece, I found the one I lost, put it back in and it fired right up, So I learned to make sure and keep track of all parts. Thanks for the help.