Other Motor help

[Vumad]

Can you guys tell me what you think happened before I go any farther?

http://www.x-h2o.com/threads/129452-Onyx-G1-Sponsored-in-part-by-Tom21

Watch from the 1:00 - 1:10 mark and turn the volume up.
[video=facebook;10200902789040695]https://www.facebook.com/photo.php?v=10200902789040695&set=vb.1494233296&type=2&theater[/video]

My ski was running great. It GPS'ed at 50mph which is appropriate for the setup I have. It started right up 1st push of the button, idled perfect. It made awesome power and pulled hard from right off idle to 50mph. I had no bogs, hesitations or any indications of problem. No tach so I don't know how much RPM i was turning. I was cavitating some in the corners but overall my ski ran amazing.

Then all of the sudden this happened. It was about the 8th lap around the track hard on the throttle. You can see in the video what happened. It ran great, I rounded the corner, it bogged, made horrible noises, didn't respond to the throttle and died. I had twin 500 gpm pumps running, the hull was dry, and my new hood design takes on very little water in the corners (ran the go pro inside, and the bilges never pump on the track).

I got towed, put it on the trailer and checked the plugs. They were black. Piston tops looked good. I started it and it fired right up, idled and rev'ed properly. I thought it was vibrating a little more than normal, but nothing like omg this thing is F'ed up.

So today I took it apart. Everything looks perfect. I turn it by hand with the head off and it spins super smooth. Before I go any further and make this more compicated than it needs to be, is there anything other than a crank bearing that can cause this? and anyway I can know for sure it's not the crank w/o disassembling the motor.

To me, everything looks perfect, and I don't want to spend extra money on unneeded gaskets and time waiting on them to arrive to reassemble if there's nothing wrong.

Thanks.

Rear -------------- Front

 

[Vumad]

PS. I was making WOT runs for the full length of the lake a few days before. The plug test (WOT to stop button, check plugs asap) were brown with a few lighter spots, so I gave it another 1/8th of a turn richer on the top. I don't think my carb tuning is the problem, but I'm open to any input from those more experienced.

Edit: Compression was 140/140 after this all happened, which is that same as it was when I put a new top end on it.

 

[Freakrider]

Your piston wash is very safe and on the rich side.

 

[Freakrider]

There are at least two crank test you can perform with your motor with the head off. First is check for excessive tolerance in rod bearings top n bottom by bringing pistons just past tdc and while holding coupler push piston down with fingers and listen and feel for play. Second is to check for a twisted crank by comparing pistons that they are in sync at tdc and bdc.

 

[Lucaumpits]

It looks like you have a rag in your exhaust ancake:

 

[Dmac80sc]

Where are the air intakes on the hood?

 

[Vumad]

Where are the air intakes on the hood?

Above the hood latch. The cowling is now part of the hood and the air comes in at the top of the seat and through the hood liner on both sides of the steering. The seat hasn't been installed yet but will sit almost flush to the cowling/air intake.

 

[Speleopower]

Odd for sure. I have gotten a couple plastic bags and seaweed stuck in my pump that caused bad vibrations and cavitation.
Good luck-

 

[tom21]

lol maybe you ran out of air!!! or a needle got stuck. something stupid happened. hard to tell exactly from the video as the "horrible noises" sound like you pulled the choke and it bogged and died. maybe you ingested a fish? lol

you should be relieved you didnt burn a top end or throw a rod. I'd do a complete inspection of the crank and driveline and check for dings in the impellor(fish?) put that ada on and take a nice practice lap and see if there is any noise.

 

[Vumad]

lol maybe you ran out of air!!! or a needle got stuck. something stupid happened. hard to tell exactly from the video as the "horrible noises" sound like you pulled the choke and it bogged and died. maybe you ingested a fish? lol

you should be relieved you didnt burn a top end or throw a rod. I'd do a complete inspection of the crank and driveline and check for dings in the impellor(fish?) put that ada on and take a nice practice lap and see if there is any noise.

I'm going to split the cases and check the crank bearings on Monday. Everything looks great but I'd hate to have a bad bearing grenade on my minty top end.

Motor gets plenty of air. Believe me I am very relieved to see the inside of the motor is in such great condition. I'm going to put that Ada you got me on but I wanted to so some testing first to make sure I wouldn't ingest water and destroy my new parts.

 

[phreeride215]

Vumad, Is that a 650 or 750 motor? What are you running for an ignition system? From your video, it looks exactly like the problem I had with new plug wires spliced into a Kawi coil. It was fine for about two years with the NGK wires, then it just crapped out.

 

[phreeride215]

Who did your porting? If my engine looked like that, I wouldn't show my mom the pictures,

 

[GIL]

I would like to think the problem is obvious. You don't use Honda wax!!!

 

[Vumad]

Vumad, Is that a 650 or 750 motor? What are you running for an ignition system? From your video, it looks exactly like the problem I had with new plug wires spliced into a Kawi coil. It was fine for about two years with the NGK wires, then it just crapped out.

750 XI SS motor with the electronics from the same ski.

 

[Vumad]

Who did your porting? If my engine looked like that, I wouldn't show my mom the pictures,

It's not ported. It's stock bored 0.75 over.

 

[ridethelip]

Is cylinder deck flat? Those piston tops are awfully clean. Steam clean.Sometimes on saki's around cyl. head studs the threads are raised making sealing very difficult.Pull studs check with straight edge or lap cylinder to see low areas and surface deck of cylinder as needed. What was the color of the exhaust when ski lost power?