if valves were drastically out, he would not get a good compression reading, long story short did u check your fuel issue? dump some fuel down the spark hole or start shooting carb cleaner down the carb and see if it fires, almost allways a fuel issue it seems

 

Thats what I was figuring as well. I shot carb cleaner right through the carb at WOT and it won't even pop at all. Petcock flows fine, I'll have to go through the carb again to make sure all is well but something just seems fishy.

 

Guru huh [img]i/expressions/face-icon-small-smile.gif[/img]

Sounds like you have checked most all of the normal things, and now just go dbl check that the info you used was correct (timing marks etc).

The only thing that stood out from your descriptions was the bad spring in the decomp on the cam as this is not used with the hotcam, and could very well be causing your problem.

From memory what happens is the cam opens the valves sooner and closes them later and if used with the decomp you will cause a loss of comp when its needed to make the engine fire. I could be wrong, but I think that is the explation. It would still make comp on a guage, but not as much without the decomp etc.

Another thing that is good to keep in mind is that you really cant set up this engine 180 out because it fires on each stroke (twice per rev etc) and if it was out the cycles would just swap.

Now since it looks like you have checked the basics of what any engine needs to run (comp, fuel, spark) now start looking at things that are specific to this engine like the aftermarket cdi box (as mentioned earlier) high enough cranking speed, starter gear clutch bearing etc.

Only other thing that comes to mind is what actually was wrong originally, how it was fixed, and what other things the initial problem could have effected that could make it not fire.

Hope that helps...

 

Thanks for the reply. It actually isn't the cam decompression spring that broke. That spring was removed when the cam was installed. The broken spring was on the cam chain tensioner mechanism itself, not in the valving. It has the stock cdi as far as I know. Before tearing into it a few weeks ago, after cleaning the carb, it did actually fire up and run like it should (soundwise....with the exception of the slapping cam chain as this was before I fixed the tensioner) for a minute or so until I turned it off with the key. It has never come to life since then.

 

Just to get the CDI question out of the way did you check the letters on your CDI yet or is the quad not within reach?

 

No, I didn't check them. I'll post them tomorrow when I head into the shop and we can go from there. Is there a way to determine the numbers or code on a stock cdi vs. aftermarket? Thanks

 

I believe a stock one should have "HN1" on it but it's been awhile. There are many people on here that have one in there garage and could double check that. My White Bros. one had a WB on it. Others are marked with their logo. Not saying this is your problem, but it's so easy to check and so many people, including myself, have learned the hard way that you might as well check in. It's under the headlight on the right frame rail if you don't know. You can slide it off the frame rail and if you pull the little tabs outward it will just slide out.

If it's not that, it's time to just pull start the thing.

 

Sounds good. I do know right where the rev box is at so I'll post what I find tomorrow morning. I'd really appreciate it if somebody could post what their factory boxes are stamped for comparitive purposes. Thanks in advance...

 

Lets not take for granted that your spark is good enough or that your compression is high enough.
The spark should be a blue and should "crack" when it fires and you should be checking it at the plug electrode. If it is orange and weak, this is your problem. I got burned on this once before and found a bad plug cap only after an engine tear-down and a considerable parts purchase.
A weak spark can run the engine but only in perfect conditions. This may be why it started for you once.
You said that you planned to replace the plug, did you do that yet?

What was your compression reading? I don't have specs on the 400 but I would guess that it Should be well over 130 PSI.
I love those good deals where a guy gets frustrated and sells out. If you are in the right place at the right time and have money, it can be profitable. I won't ask what you paid but I'll bet you got a good deal.

 

When my 400 doesn't start, I throw a new plug in it. That has worked every time so far.