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Discussion Starter #1
I put about 13 miles on a short ride around town. It runs good!

I only ran it up towards redline once, and it acted like it hit a record limiter at 8k. Fine otherwise.

I noticed a whiring noise now, and it's hard to get into neutral at a stop. It's fine when moving slowly or engine off. I did drill out the basket and resurface the clutch plates, so I wonder if that's it. It idles lower in gear with clutch pulled, so I think the clutch is grabbing more than it used to.

At idle, I have a ticking noise from the left side of the rear cylinder. It goes away off idle. I am uploading it to my Google album. It will be at the end, along with pictures of the spark plugs. The plugs might not be accurate. I slipped on the mufflers briefly to better hear the tick. It isn't tuned for mufflers.

https://photos.app.goo.gl/MvU3U33ddipteaD46
 

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Discussion Starter #2
Nevermind. The engine just seized.

On an unrelated note, anyone looking to buy a 1989 VN750 with a freshly rebuilt engine?
 

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Nevermind. The engine just seized.

On an unrelated note, anyone looking to buy a 1989 VN750 with a freshly rebuilt engine?
Whaaat?!! How did that happen,?

Sounds like maybe it wasn't oiling?

That's horrible, man. Was trying to open the video a few minutes ago but ended up in my own album somehow.

Couldn't find the video, but the two spark plugs at the bottom of the page look lean.
 

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Discussion Starter #4
I have spent too much time on this to go at it again. I'm not giving up on the bike as a whole, but I'm taking it to a shop now. I gave it the old college try. I'll let you know what they find.

I wonder if the misplaced rocker stressed a valve spring, and caused it to break later. If it was able to hold the valve open when it shouldn't have been, it must have really pushed down on the valve when it should have opened.
 

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When it stopped, was there any bad noises or did it just slow to a stop? Does it still crank?
 

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Discussion Starter #6
It lost power crossing 4.5k. I pulled in the clutch and pulled over. I heard some metallic noises and the engine stopped. It will not turn over by starter or pushing it in gear (even 5th gear).

If the valve spring gave out, the valve would have dropped and hit the piston.
 

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Does sound like it could've swallowed a valve.
 

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Discussion Starter #8
Does sound like it could've swallowed a valve.
I don't know what that sounds like. However, I pulled the spark plugs so I could shine a light in and see if I could see anything. Nothing looked out of place in the rear.

Both front plugs however, are smashed! I stuck a zip tie in and it came out with oil on it. I put a screwdriver in and it catches one something. Shining light in there, I see dings on the cylinder wall, and some metallic mass on the piston.

I think it was actually a front valve that let loose or something. Maybe the timing chain jumped a tooth? I think I can get the front cover off.
 

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Discussion Starter #9
How about a snapped rocker?!?

I think the timing is still correct. I have to draw it out on paper to see where it should be.
 

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Hey, be careful around that valve in the first pic of your last post. That valve stem is about to slip loose from its keeper. The spring will take off like a rocket.

I'd say the head has broken off the valve stem and the chunk slapped around in the chamber, smashing the plugs and the piston. When that happened, it also broke the rocker.
 

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Well, it depends if there's any tension still on that valve spring. If the stem broke straight off , the spring may be just sitting there with no tension.
 

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Discussion Starter #12
I worked out the math for where the cams should be. The engine stopped at 50 degrees BTDC. That puts the intake cam at 290 or 110, and the exhust at 20 or 200. Looking at the lobes, that's about where they sit. If timing is off, it's a tooth or two, not way off.

Upper tensioner had decent tension. I know the piston in and broke off the valve. I just don't know the sequence of events that started the destruction.

Thanks for the warning! I would hate to have that caught in my eye.
 

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Discussion Starter #13
I'm not sure if you can quite make it out in this picture, but it was the left side intake valve that dropped. The right side just got smashed as a result. You can see there is nothing remaining of the valve stem. The Rocker is intact, though damaged. It shook around and hit the housing in one spot.

My theory as far as the sequence of events goes, is the front left intake valve let loose while running. It dropped into the cylinder, whereby it ground itself to a pulp. On one (or more) revolutions, the right front intake valve collided with the broken valve in the cylinder, snapping the rocker clean in two. From the top side, there doesn't appear to be any other damage to that valve.

I haven't found any evidence of the timing being incorrect. The cams are sitting right were I would expect, given the resting position of the crankshaft. The front cylinder was running strong when I had issues with the rear cylinder a week ago. It tested well on a leakdown test. No strange noises when running (including holding a screwdriver against the engine and my ear. I never removed or messed with the valves during my rebuild.

I think the valve just coincidentally gave out right then and there.

I will add high res pictures to the album linked above.
 

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Valve might've stuck open, then got kissed by the piston.
 
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