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Discussion Starter #1 (Edited)
A few months ago I was riding with some friends and threw the drive chain twice. When the machine was new, I threw the chain and cracked the case under the gear selector shaft. Patched it up well enough that it barely leaked and ran it like that for years, so I never put a good case saver on it. It finally caught up with me. Recently, I threw the chain and rolled it back on and started back for an adjustment check. But I did it again on the way back. It was a violent, sudden stop for the engine as the chain piled up on top of the gear selector shaft. After that, it had a no start condition. Nothing sounded crunchy inside when cranking, so I tried a pull start; still nothing. Tore it down recently to have the case repaired and replace the selector shaft. Figured the gear position sensor wires had gotten pinched (It looked that way, but the casing was unbroken) and it would be an easy fix. Tested them for continuity today; all seemed well. Had both case covers off, nothing looked mangled. Pulled the flywheel off (With the correct, safe tool) to check out the key; all looked well. Pulled the clutch off to remove gear selector shaft; all seemed well. There was a bit of play between the transmission input and output shaft, but I think it's always been that way. Had the valve cover off; no broken cams. Honestly, everything easy to see inside the case covers looked brand new. My mechanical experience inside ATVs is limited. Is the flywheel rubber bonded like on a car engine? Could the outer piece of the rotor have shifted? Again nothing on the rotor or any other internals looks mangled. Could the sudden stop have toasted any electronics? I didn't check compression. Any ideas or missing info I need to add would be appreciated!

Edit: It's an '07, not an '06. Shouldn't matter though?
 

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One thing to check, I have seen the cam sprockets spin on the cams after a sudden stop like that, which would throw your timing off. Take a pic of your cam sprockets and the lobes on the opposite side at TDC. They should be pointing at 10 and 2 o’clock position.
As far as I know, the flywheel is a solid piece.
 

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Discussion Starter #3
One thing to check, I have seen the cam sprockets spin on the cams after a sudden stop like that, which would throw your timing off. Take a pic of your cam sprockets and the loves on the opposite side at TDC. They should be pointing at 10 and 2 o’clock position.
As far as I know, the flywheel is a solid piece.
Thanks! I'll be sure to check that out and grab a few pictures next time I'm into it. After stopping at the shop i bought it from, cams were my next stop.
 

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Does it have spark? The stator wires are in the same area. If one of those got broken, or are touching another, or a ground, it could stop the ignition from working.
 

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Discussion Starter #5 (Edited)
One thing to check, I have seen the cam sprockets spin on the cams after a sudden stop like that, which would throw your timing off. Take a pic of your cam sprockets and the lobes on the opposite side at TDC. They should be pointing at 10 and 2 o’clock position.
As far as I know, the flywheel is a solid piece.
This looks right to me? The TDC mark is a tiny bit off the center of the sight... but the paint mark didn't move on the one painted cam/sprocket. With the sprocket arrows aligned, even with the sight a bit off, that's just how it was built, right? Lash looked good too. A 0.004 feeler fit perfectly with the cams positioned as pictured. Didn't bother going any further checking lash. Chain is tight.
49426
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49427
 

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Discussion Starter #6 (Edited)
Does it have spark? The stator wires are in the same area. If one of those got broken, or are touching another, or a ground, it could stop the ignition from working.
The stator wires I tested after the gear position sensor had continuity... that's not saying two of them couldn't be touching in certain positions. And I was so focused on the case damage, I never did test it for spark. Think a buddy might have after we drug it back to the truck...

I'll test compression next, since the engine is still on the floor/bench and not in the machine, I won't be able to confirm spark until it's welded. I'll be sure to get some before and after pictures of the damage for fun.

Things I'm considering could be wrong now: If compression is low (looking for 142psi, right), could the decompressor be stuck? If it was spark afterall, could the stator/CKP be bad? Or, if it's spark, I could have a cracked magnet/flywheel issue?
 

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This looks right to me? The TDC mark is a tiny bit off the center of the sight... but the paint mark didn't move on the one painted cam/sprocket. With the sprocket arrows aligned, even with the sight a bit off, that's just how it was built, right? Lash looked good too. A 0.004 feeler fit perfectly with the cams positioned as pictured. Didn't bother going any further checking lash. Chain is tight.
View attachment 49426 View attachment 49425 View attachment 49427

In that last picture, the line by the T should be in the center of the hole. The cams should be lined up at that point. I think you may be a tooth off. Being a tooth late with the cams makes pretty good odds for the exhaust valves to get hit. Your cams are pretty late. It would be a good idea to do a compression test after you get this all ironed out, or a leak down test would be better yet.
 

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Discussion Starter #8
In that last picture, the line by the T should be in the center of the hole. The cams should be lined up at that point. I think you may be a tooth off. Being a tooth late with the cams makes pretty good odds for the exhaust valves to get hit. Your cams are pretty late. It would be a good idea to do a compression test after you get this all ironed out, or a leak down test would be better yet.
I'll have a look at getting it in time then. Thanks for the insight!
 

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0.004” is at the limit for too tight. I assume that is on the intake side. Need measurements for all 4 valves. I agree timing looks off a bit. With T mark in the window (not the actual T), set exhaust cam first, then intake cam. Spin by hand for 2 revs, and check that it’s right before closing it up.
 

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Discussion Starter #10
0.004” is at the limit for too tight. I assume that is on the intake side. Need measurements for all 4 valves. I agree timing looks off a bit. With T mark in the window (not the actual T), set exhaust cam first, then intake cam. Spin by hand for 2 revs, and check that it’s right before closing it up.
Set timing according to service manual and ended up with what I have now being the closest possible. One tooth either way put the indicator entirely out of the window. Could the chain just be very stretched? Maybe the forward chain guide doesnt have enough convexity? Maybe the cam chain drive sprocket on the crank has moved? (Didn't take the primary gear off the crank. Assuming it's keyed as shown on the assembly diagram.) I could always go through the lovely work of degreeing it once it's assembled and if it does have spark.

Also, here are the lash results:
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If I had kissed an exhaust valve, I'd think my exhaust lash wouldn't be so near to the low-end spec.

I'm still at a total loss here... still think my next step, before or after welding and machining, will be compression.
 

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Where do the cams fall when the T mark is in the center? If a tooth either way throws it off, the chain may very well be stretched out.
The lash looks pretty good. It definitely is close enough to start.
That said, if the cams are running late, via a stretched chain, the compression will be lower than it should be. Possibly too low to fire with a compression release.
 

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Discussion Starter #12
Where do the cams fall when the T mark is in the center? If a tooth either way throws it off, the chain may very well be stretched out.
The lash looks pretty good. It definitely is close enough to start.
That said, if the cams are running late, via a stretched chain, the compression will be lower than it should be. Possibly too low to fire with a compression release.
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That's about how far off it is with the balancer mark aligned. Supposed I could do the decompressor inspection in the manual. That's just making sure it's a smooth operation I believe though.
 

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Timing looks good on that side and valves within spec. It should fire assuming you have good fuel, good spark, and no wiring issues. If it doesn’t, I’d check compression next.
 

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I agree, none of this should keep it from running. It doesn't look as bad looking at it this way. I've run stuff that looked like that. You will want to get a chain soon though.
 

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Discussion Starter #15
Threw everything back together today, and for whatever reason the bike runs! I'm assuming two+ of the wires between the stator cover and drive sproket were pinched and communicating. Will probably cause me problems down the line... but who knows.

Now, having an issue of fuel spraying out the bowl drain tube when cranking/running. If I loosen the drain bolt, it runs out, but actually sprays out when running and the bolt is tight. Have to play with the throttle to keep the bike running. Guessing the carb just needs a good clean after sitting. If there's anything else it might be, I'd appreciate the info before I tear it out.

Here's an idea of the extent of the crack/chunk that was smeared off:
49481


Had some wrap and silicone laying around from another project, so I threw some on. Help or not, doesn't matter because it was free and it's just a stock pipe.
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Bike still needs a lot of work to make it look as good as it did the day 15 year-old me rode it, after looking at bikes all afternoon, but I was thrilled to hear it run.
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The fuel leaking is either from something stuck in the float needle seat or the seat has dry-rotted and cracked. You can order the needle and seat in a carb kit if cleaning it out doesn’t help.
 
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