Broken DASA Power Valve

K

Ken23

Location
USA
I definitely believe water can be getting to the guillotine when we nose in a back flip and the ski goes all the way under and we ride it out. I have to assume some water is sucked into the carburetors which is definitely entering the cylinders which could be getting to the guillotine.
 
I

Iconicsuperpoop

Location
Here
Ken23, can you get a closer pic of the fracture? End on, and from the side? It's hard to see if it's porosity in the casting, or a stress fracture. And, is that a shadow from an uneven break, or a gap? The valve blade shaft itself looks out of round.
 
DAG

DAG

Yes, my balls tickled from that landing
Location
Charlotte, NC
JC's picture looks like its from a tensile test. The forces required would be in the 1000's of lbs, not the likely culprit here. Likely a fatigue fracture which happens at a order of magnitude lower strength. Not so sure about side loading, id assuming there would be a lot of galling on the post and hole if it was
 
Kaylee.S

Kaylee.S

Location
Redondo Beach, CA
False. I can answer in more detail later when im not at work. All we know is it failed along the plane of maxium shear. Really need a closer picture to determine failure mode and propagation. Torsion failures of ductile material and fatigue failure look an awful lot like a tensile failure of brittle material to the untrained eye.

@DAG @Jr.
 
Jr.

Jr.

Standing Tall
Staff member
Site Supporter
Location
Hot-Lanta
Look at the operation of the Giotine and how its supported when its in service?
There is little to no side loading, unless the top bellows mount is not machined square?
I doubt the cap install screw torque had anything to do with it?
And likewise, not water related. No piston impact is being reported either?
Its a simple push / pull operation. Distance of trave is only 10-15mm The OP stated second failure in same slot?
That leads me to believe its some sort of clearance / machining issue?
Or possibly mis matched parts for the application?
 
I

Iconicsuperpoop

Location
Here
Close ups, please. Kinda looks out of round, with stress from pressing. But, alas, I'm just a simple bloke that huffs 2 stroke.

I like cheesy poofs, so it may be the powdered cheese residue obscuring my view.
 
DAG

DAG

Yes, my balls tickled from that landing
Location
Charlotte, NC
I'm kinda confused how their is no reported piston or ring damage. If the guillotine is disconnected what preventing it from contacting the piston?

1537299438226.png
 
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K

Ken23

Location
USA
DAG Luckily for me the stem broke off above the stop, not allowing the guillotine to drop into the cylinder. I am concerned that the shinny spot on the guillotine is an indication that the rings did make contact.
 
DAG

DAG

Yes, my balls tickled from that landing
Location
Charlotte, NC
Ken23 said:
DAG Luckily for me the stem broke off above the stop, not allowing the guillotine to drop into the cylinder. I am concerned that the shinny spot on the guillotine is an indication that the rings did make contact.
Click to expand...
I bought a off the shelf nothing special DASA 970 some years back and had a PV contact the piston and the guillotine was in one piece. DASA may have changed the design in the past few years but just wanted to double check are you 100% sure it didn't make contact?
 
I

Iconicsuperpoop

Location
Here
Fitment/ pressing stress? I wish I could see this in person. (still looks like a very porous casting)

You have a GOOD machine shop/ foundry near you? Tool and die maker/ inspector would be perfect for this mystery.
 
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