Nytro misfiring, closed spark plug gap

[UncleBubbles]

Brand new to this site, fairly new to Nytros, but sledding is well known to me. I have a nytro missing on the center cylinder. I went for a ride a few weeks ago, the sled started fine cold, got to our meeting spot with the group, shut it off, tried to start it 20 minutes later and it would turn over but not fire, was flashing code 34 on the screen. (I know now that is a code for the center coil) I disconnected the battery and reconnected it and it started with no code and ran fine. Half way through the ride I was on a a straight away and let out of the throttle completely, and it backfired HARD in the intake, I saw snow dust puff out of the vents when it happened. Stopped on the trail and looked it over but couldn't find anything. Then late in the day it went down to two cylinders without any warning. Happened at 90mph on a lake, again stopped and looked it over and again didn't find anything. So now today I am tearing it apart and I've got the plug out of the center cylinder, the gap is closed and there's a mark on the ground where something has come and hit it. I am pretty sure all three of these events are related, closely. Has anyone experienced something like this? I have a bore scope and will try to have a look in the cylinder, but I don't know if it will fit into that wee little spark plug hole. How difficult is it to lift the head with the engine still in the sled? Any recommendation are welcomed!

 

[canoehead]

Well if anything hit it, it was the piston........Mmmmm, what are you running for plugs?

 

[UncleBubbles]

The plugs are stock nytro from the factory, NGK CR9E0.

The story gets better, I couldn't compression test it, nor bore scope due to the tiny plug holes, so I unbolted and lifted the valve cover... center cylinder first intake valve lifter is shattered and stuck in it's lifter bore, thus causing the valve to stay in the open position.. which means the piston meet the valve.... which likely means a broken piston... which will mean a scored cylinder... which would be the final straw for this shortblock. I have pictures I can post up if anyone is interested

 

[moab11]

yes, please do post pictures. Failures on these motors are so rare, it's always good to see what happened and hopefully prevent it.

 

[canoehead]

Did you just buy this sled???

 

[yamafreak]

pics would be great

 

[UncleBubbles]

It's my brothers sled, which I have plans to buy. Interestingly, this sled has had a relatively easy life, with only 1900 miles on it, its never been boosted or sprayed, raced or anything of that nature.

 

[UncleBubbles]

Is there a way to time these motors while its in the frame to pull the head? Or does the engine need to come out?

 

[canoehead]

Ouch! What oil has it been running?

 

[UncleBubbles]

Yamaha spec oil from yamaha, not sure what weight it is. New theory, what has happened is the cam chain tension bolt, backed out and fell out of the block. This allowed the cam chain to loosen right off, which then allowed the cams to jump teeth backwards and forwards on the chain while it was running. I believe the intake cam gear jumped two teeth forward (or tried to to) the intake valves tried to open, directly into the face of the piston. I'll know for sure when the engine comes out and apart.

 

[canoehead]

I'm thinking that the 08's and earlier had a recall for cam tensioners.