We have the 400EX back together, and we've done the basics. Getting spark at the plug, pulled the carb and it's shooting gas into the cylinder. Every time we pull the plug it's wet with gas but that's after spinning it for a while. We were very careful to try to get the timing right back on but I'm wondering if that's our problem. It almost has to be. Either we're dead on or off 180.

Looking through the inspection hole there is a groove in the top where the plug screws in. Lined up with that groove on the flywheel was a line with a sideways T beside it and right behind that was a hole. Then on top of the cylinder we laid the cam lobes down and there is 3 lines on the cam sprocket, one pointing straight up (right near a stud bolt that holds the sprocket on) and two lines exactly parallel with the cylinder head. Now did I install this right or wrong? I'm practically convinced that is our problem because I've fooled with irrigation engines enough to know we should be running unless my timing is off.

Help, we're going to work on it again tomorrow evening. Now if that damn service manual would come in we ordered!

Thanks. Kyle

 

had a problem like this try pull starting it the compression release causes problem sometimes.

 

It sounds like you did. Make sure the mark you time it to corresponds to TDC by putting a small screwdriver in the spark plug hole and noting its up and down movement. You can't get the timing 180 off because the spark trigger is crank mounted. Since the cam spins half as fast as the crank, there is a spark every TDC, compression stroke or not.

 

Going back together, I want the cam lobes facing down right? It was smooth across the top of the cam if you were to run your finger across.

I want both sets of valves closed at TDC, right. Exhaust valve opens on the pistons downward cycle, closes, and as the piston comes back up, the intake valves open more or less. 4 strokes fire every other revolution I know.

I have the timing mark lined up perfectly in the hole with the sideways T right behind the mark on the flywheel. The piston is at TDC, pulled the plug and checked. Now what?

I'm completely stumped here. Never been in a 4 stroke motorcycle engine although I know how they look inside. She turns over and over, like the ignition is off (already checked that). When we quit last night, near the end it was kinda trying to backfire but still wasn't trying to run. Before we took it apart, it always fired right up, smoked like a freight train, but would start.

 

Trailblazer sounds like everything is go at Houston, I will be willing to fax you over some of the factory manual pages to look at I tore mine apart and replaced the cam, piston and head work when I put it together I followed the book to the tea and it's the first time I tore down an ATV like that and it fired up right away, did you adjust the cam tensioner right or even mess with it??? If it is adjusted wrong it could knock off the timing just enoug to give you fits. PM if you have a fax and want me to send you a fax on the specs how to put it together and double check it, sounds as if your reall close, remember the 400ex has a power valve in the carb if you push the throttle it will flood very easy for it will keep pumping gas in the head.

 

jim, I sent you a PM. Thanks.

 

Checked the compression if low you timing may be out.

 

I didn't realize I posted this under the question I asked the first time. In case you guys didn't notice it I copied and pasted what I wrote below.

IT WAS THE VALVES!!!! Valves were too tight, readjusted them, VIOLA, started right up. I knew we put the thing back together right. Fixing to break it in. Thanks all

Well, we started it up and it ran for a couple of seconds so we went in and ate supper, come back out to break it in and she won't idle on her own. While fiddling with the idle control screw, my brother in law tried to keep it from dying, not always successful. It died half a dozen times and refired back up fine. The last time it died, it won't fire back up for nothing. So I guess it's back to more hair pulling.

All this being said, I had to pull the head off of my Suzuki 500 4x4 because it was ticking and one of my exhaust valves slipped. A lot more to take off of it to get to the engine than the 400EX. When it rains, it pours don't it?

 

KTK, now you have me really confused. [img]i/expressions/face-icon-small-confused.gif[/img] The exhaust valve should open at the bottom of the power stroke to.......well.......exhaust the exhaust. In other words, the piston comes up primmed with fuel and air, the plug lights the mixture off at the top of the stroke, the piston travels down and at the bottom of the stroke the exhaust valve opens and the piston travels up to push out the exhaust, at the top of the stroke the exhaust valve closes and the intake starts to open as the piston travels down to suck in a new mix.................
But you said it started? Hmmmmmm.................. [img]i/expressions/face-icon-small-confused.gif[/img]

 

Doc I think your spliting hairs, we all know what he was talking about. Some people can put it into words better than others.

Let's all be glad for the fellow that everything is in order and is up and running.