JayDee

That's what I was wondering, the line continuing all the way around to the outside of the head is what threw me off. And yes, the valves were set .006 on the compression stroke, this isn't my first rodeo. I never touched the cam chain, I didn't see a reason to dig into the front cover as the lifters are pushrod driven. There also aren't any signs that this engine has ever been apart, but of course I bought it as a non-runner. Your experience with that Rancher is what others had mentioned, which is why I pulled the head again to check. But, neither seat nor guide appear to be out of place. I should clarify something, given your responses you seem to be under the impression that the engine was pulled and the case was split for thorough examination. That isn't the case, this was simple cleaning with a piston/cylinder kit assembled in frame. As for the rods, I've worked on several of these machines over the years and almost all of them were ranch rigs that were beat on every single day. One was even ran out of oil twice, but still ran like a sewing machine even with 18k miles. Not once have I seen a bad rod. Generally, you can check for end play with a dial indicator while rocking the crank, which is what I did for the bottom end. If it was shot, I wasn't going to invest anymore time into this engine. Now, as I had to practically drive the wrist pin on, safe to say that isn't a problem either. The machine has great oil pressure, so I once again didn't see a reason to dig that deep.

I wish I would have got some video of the sound before I disassembled the machine again, but this video I found is very similar to what mine is like:

Funny that you should mention that... I did the first start break in and let it cool off. Everything looked and sounded good. Changed the oil and put a few miles on it today. Firm shifts and all kinds of power. HOWEVER, after getting warmed up, I noticed a clanking sound from the top end. It is RPM dependent and is only present above 50% throttle (which I did not exceed during initial break in). I double checked my valve lash and it is perfect. After some reading I found others that had encountered this issue after a top end rebuild and even a few that had replaced the timing chain without solving it. Given the nature and location of the sound, I took the cylinder head back off to investigate. Piston and cylinder still look great (I checked the rod before I even ordered a piston kit to see if it was worth rebuilding), valves and guides looked fine. Though the exhaust valve has a little more play in the guide than I would like, it is comparable to the other Foreman 450S with over 15k miles that I had apart last year. That ATV runs like a swiss watch! Anyway, I noticed inside the intake port was either a casting line or a crack? Given how well it runs, I can't imagine that is the issue, but I thought I would ask before taking it to the machine shop.

Ordered a cylinder kit, got it put back together and running. Here's some new versus old parts. (Note, broken skirt on the old piston was from dropping it on the shop floor.)

We've had non-stop rain here, so I took advantage of my free time and cracked open the Foreman. Looks like the diagnosis was spot on, she was ran HOT

Well, I have good news and bad news... The good news, the new pulse generator pickup came in yesterday. I installed it and buttoned up the machine. While cranking, my meter was still showing 0.1v AC, same as the old pickup. But, I also orderd an inline spark tester this week, so I tried it out. We have spark! Now that brings us around to the bad news. We have spark, we have fuel (even ether) and the machine still won't start. I have never seen a machine with so few miles with low compression, but here we are. I should have known given how it is by far the easiest pull start out of the entire fleet. Unfortunately, I don't have time to tear into this motor right now as Spring planting is right around the corner here on the farm, so this one will be parked in the shed for a little while. But I at least wanted to update this thread and let everyone know that the mystery is finally solved.

Thanks @AKATV for the info on the flywheel and the testing procedure. I was mistaken, I was testing the pulse generator when I did my first round of diagnostics. Silver lining, the pulse generator is actually shot, so I would have had to pull the assembly anyway. Funny though, on my yellow 2000 Foreman 450S, I saw as high as 70V AC on that pair of wires so I assumed it was the stator output. That machine was also a non-runner when I picked it up but it turned out to have just a bad CDI box. Anyway, new pulse generator is on the way, I'll report back when it gets here and I put the machine back together.

That could be, though I wonder why they would replace the flywheel? Anyone happen to have one laying around that they could measure?

Oh sorry, yes I checked that and no continuity from yellow wires to ground. By the book, the stator is good...but I still wasn't getting any AC output on that blu/ylw wire which is why I pulled it. What else could it be? Pulse generator maybe?

I just finished this test and between each yellow terminal I was seeing exactly 1.0 Ohm. HMM.

Negative, I was checking for output voltage on the grn/wht and blu/ylw wires that run from the stator all the way to the CDI box. Thank you though, I will do a continuity check when I run back out to the shop. Also, I can definitely see that scenario roasting these stators, especially the ES models. That said, it makes me wonder how my neighbor's S model is still alive. The battery in his machine has been shot for several years and he has been too cheap to replace it. I mean, the display doesn't even light up when you turn the key, only after pull starting it!

That is possible, though that wouldn't explain the lack of AC voltage being produced by the stator reading directly from the plug.

Well, today was the day, I pulled the stator and unfortunately it looks like someone has been in here before. Though the stator doesn't have any noticeable shorting going on, I do see chips and wear spots. What do you guys think?

Thanks @AKATV and yeah, I know the jumper cable car battery hookup isn't ideal, but it was running down my spare ATV battery too quickly doing all of that cranking during testing. So the ATV battery would sit on the charger while I worked on diagnostics. The stator should produce AC voltage while cranking regardless of the battery condition though, if I remember right. Funny, I worked the buttons with some WD-40 this evening and we have headlights again! Check off one problem. That leaves the biggest one...

Thanks for the suggestions! I wire-wheeled both grounds on the crankcase and the adjacent ground on the frame. Still no spark and screen still resets while cranking. I even clipped my jumper cable straight to the crankcase ground, but no change. I disconnected the plug on the frame for the stator/pulse generator and plugged my multi-meter into the blu/ylw and grn/wht leads, just to bypass as much of the harness as possible. Getting all of 0.1v AC while cranking. I hate to say it, but the more I dig into it the more I keep finding myself back at the stator. How bad is that job on these? It looks like there is almost enough room to replace it without pulling the motor. Also, here is my fuse box. The wires toward the bottom were taped off, any idea what they run to?