Trouble starting

[fauxamish]

I am having trouble getting my 2000 400ex to start. I can only get to the bike on the weekends, as it is at my dad's house. Last weekend, the bike started normally, I went out and rode for a little bit and then put it away. This weekend, I changed the float bowl gasket and turned the air/fuel screw in a 1/4 turn, due to a fast idle (i tried the idle adjustment screw, but it wasn't touching.) When I went to start it to see if the idle problem was fixed, the bike cranked and cranked but would not start. I adjusted the air/fuel screw back to how it was and still nothing. Eventually I got it to start and it ran kinda rough and idled really low. If I gave is some throttle, it revved and ran ok. It then stalled and would not start again.

I got a new spark plug because the spark seemed kinda weak with the old plug and the tip was black/sooty. With the new plug, it would not start.

I bought a coil off eBay but it will not come until the end of the week, and I cannot get to the bike until saturday. Does anyone have any suggestions in the mean time?

Some things that might or might not be important: The bike was recently jetted... it ran lean before that, but it ran. After jetting it idled really fast! like 3/4 throttle. I took the carb back apart and turned the A/F screw in a little bit. It ran, and that was last week when it was still a little fast. My rings are worn and I'm burning oil, but I do not think the compression is bad enough because I can still do wheelies through 3rd and lift the front in 4th. There was still spark so it is not the killswitch... Any ideas anyone? Thank you.

[rideracelivemx7]

soudns like you sucked up some junk, and sounds like the pilots cloged. did you jsut get a new main? whats your jetting, a good start would be a 40 pilot and 165 main.

[fauxamish]

Thanks, yeah, I got a new main (170) and the stock pilot. I'm running the airbox with out the lid (it did not come with one...) and a K&N airfilter.

I figured the coil could be a back-up if nothing else. I will take the carb apart and clean it all out. I'm tearing the whole thing down in a couple weeks and I have a really clean 450r carb that is going on. I just wanted to see if anything else needed fixed. I would hate to put it all back together and not have it run, you know?

[rideracelivemx7]

i ran that with my ex, it was bone stock, and i crammed the stage 2 setting down its throat lol 40 pilot and 170 main, it ran awsome and it was a nice brown plug:) deffinetly replace your pilot, i have a feeling its going to run horendous, sporatic idling and what not

[fauxamish]

yeah, the one time I got it to start, it idled really rough. I'll clean it out this weekend. Thanks for the insight.

[fivepointnine]

your pilot is waaay to small for your mods, you need a 40 at the minimum and a 42 would likely be perfect

[rideracelivemx7]

if he does a 42 pilot he might as well rip the choke out and get some more air to the hog. wont need the choke after that. quick two cracks at the throttle on start up and it will start right up.

[rideracelivemx7]

if he does a 42 pilot he might as well rip the choke out and get some more air to the hog. wont need the choke after that. quick two cracks at the throttle on start up and it will start right up.

[rideracelivemx7]

if he does a 42 pilot he might as well rip the choke out and get some more air to the hog. wont need the choke after that. quick two cracks at the throttle on start up and it will start right up.

[rideracelivemx7]

if he does a 42 pilot he might as well rip the choke out and get some more air to the hog. wont need the choke after that. quick two cracks at the throttle on start up and it will start right up.

[fauxamish]

I'm putting the 450r carb on when I rebuild (starting in 2 weeks probably...) so I just wanted to get it running and see if anything else needed fixed. I wanted to have it running when I started the rebuild so that when I am done, it should start... That would eliminate a lot of things if I had trouble later on. Thank you for the suggestions though.

Any idea what the 450r carb should be jetted for when I am done? It's gonna be a 416cc 11:1 with 450r carb, full yosh pipe, K&N... I think that is it for now.

[RaginRedneck]

Change your pilot (they are cheap). Is your filter Clean? Clean out the carb. Stop Using the A/F screw to adjust your idle, that's not what its for, there is an idle adjustment screw for that. Screwing with the A/F screw might make it idle different, but its gonna screw up another circuit.

[fauxamish]

I know that the A/F screw is not the correct way to do it, but the idle adjustment screw was not even touching the throttle... I'm gonna clean everything out next time I get the chance.

[fauxamish]

Ok, not to revive a dead thread, but I tried to start it again this weekend after cleaning out the carb (jets, everything) and it still does not start. I tried shooting starting fluid straight through and nothing. So I pulled the boot off the spark plug, put a new plug in and touched it to the frame while cranking. I got 1, maybe 2 sparks for 5 seconds of cranking... and these were the weakest sparks ever. I had bought a new (ok, new to me... not really new...) coil off eBay and put it on. Still nothing. Not even one spark. I got out my volt meter and started testing. I got about 9v (battery is getting a little run down from cranking and cranking and cranking...) at the connnector right before the coil. I tested the wire going the to spark plug and got 0.02v. I tried this on both coils and got the same or 0.

Now, I realize that both coils might be bad, but is there something else I am missing? It is getting fuel for sure. There was a ground lug between the frame and the square thing on the front of the coil. I sanded it so I have a good connection. It also started last time I rode, no problem. Any ideas would be greatly appreciated.

Oh and if Brauap starts a stupid arguement on this thread, I am going to be pissed.

[fauxamish]

Anyone?

[hoogiesngrinder]

Charge your battery. 9v is not >= 12v. Clean you battery post and cables while you're at it.

Is it just me or does 170 main sound a little much for a filter and exhaust on a presumably stock motor? I was thinking a 40-42 pilot, roughly 2.5 turns out, and 152-158 main, 4th clip :confused:

[fauxamish]

The battery is being charged. I did some searches and found a lot of people running 170 with the full yosh, filter and no lid. I am just trying to get it running again before the teardown over thanksgiving. A 450 carb is going on, so I'll figure the jetting out for that. It started before, it just wont start now. Also, the plug wasn't black when I pulled it (not that the plug is the best check anyways...)

Anyways, I still don't have spark...

[hoogiesngrinder]

There are a lot of things to take into consideration:

A coil is essentially a voltage multiplier and capacitor all in one. It takes ~32,000 volts for an arc to jump 1cm, and thats open air. A typical plug needs at least 15 thousand volts to properly fire depending on gap and other conditions inside the cylinder. A weak battery means a slower charge time resulting in a sporadic or no spark situation. The coil has to charge up to a certain voltage before it can arc at the plug and discharge, then the cycle repeats. (sorry if my math is off)

As for the main jet, they usually start to kick in at 2/3 throttle and take over at 3/4-7/8 to full. This is why the bike must be run at full throttle the shut off, coasting to a stop, and then checking the plug. The only time I've seen someone run a 170 was with a built 440 setup for oxygenated race fuel. Just my $.02

[fauxamish]

Ok, thank you. I guess it must have been that the battery got run down trying to start with the carb plugged up, and now that the carb is cleaned, the battery is too weak. Thanks.