Crank bearing failure and damage.

[yamanube]

Helping a buddy rebuild an engine. He found damage to the pistons and domes and upon disassembly the front crank bearing straight fell off the crank snout and the middle one had rashed up his cases. I think some part of the middle bearings went through both cylinders and it looks like they where getting hot.
Any speculation on the cause? Cases are pretty rough, are they re-useable?
It looks like those middle bearings where getting HOT, I would be hesitant to re-use them but there is obviously some value in the porting that would be a shame to throw away.

 

[yamanube]

@Jr. I'm sure you have seen these pics...but if not.

 

[BruceSki]

We’re those cases properly torqued? I expected to see all three locator pins pressed in to have bearing movement like that.

I’d clean them up and re install new crank with loctite bearing retainer on the outer races of all bearings where they seat into the cases.

 

[Jr.]

Have not seen these pics directly, But......
Typical crank chatter, when the crank is simply worn out! Or, was running cheap bearings?
cases need to be fully inspected and verify journal's are still round. Also make sure cases are not cracked and any epoxy work is still sound.

 

[yamanube]

It was a hot rods crank (japanese bearings) in an, allegedly, low hour engine. I question how low hour it was, the piston skirts showed a bit of wear.
I think she was also drinking some water.

 

[yamanube]

We’re those cases properly torqued? I expected to see all three locator pins pressed in to have bearing movement like that.

I’d clean them up and re install new crank with loctite bearing retainer on the outer races of all bearings where they seat into the cases.

I suspect they where property torqued but didn't build it myself.

 

[Jr.]

Hotrods cranks are not what they used to be. I no longer use them.
many say low hr motors. Unless you actually log the amount of fuel consumed?
you have no way of knowing?

 

[kevbo]

Thats fretting, they all do if the bearing is able to move in its bore. I measure the holes before assembly and surface the halves on a lapping plate to make sure they're tight. Then I use strong loctite on the bearing to case and have never had any fretting. All these cases are ruined by careless assembly.

 

[yamanube]

Thats fretting, they all do if the bearing is able to move in its bore. I measure the holes before assembly and surface the halves on a lapping plate to make sure they're tight. Then I use strong loctite on the bearing to case and have never had any fretting. All these cases are ruined by careless assembly.

So you are measuring the bore, surfacing them, re-measuring the bore then comparing that to the actual measured bearing OD?

 

[kevbo]

I bolt the cases together clean and dry and measure the bores, then compare that to the bearings. I want to see some interference.

 

[Sparkplug]

I've slapped 2 dif cases together and sent it no issues. Like 10x. Keep good bearings on the crank and it won't fret. Tye aluminum case is more than willing to yield itself to the crank.

 

[wmazz]

oops.

 

[wmazz]

upon disassembly the front crank bearing straight fell off the crank snout and the middle one had rashed up his cases. I think some part of the middle bearings went through both cylinders and it looks like they where getting hot.

We had the same case chatter problem on the 1986 and
up 650's to about 1991. I was under the opinion that these
cranks, were not strong cranks and just flexed too much.

I suspect the main bearings had some rust damage that
contributed to the bearing failures.

Look at the old front main seal. Does it have a loose or
worn out fit on the crank? Worn out front main seals
allow all kinds of garbage to get sucked into the front main
bearings.

Often front main seals wear out first on the vacuum side
(The flywheel side), and that allows the junk to be sucked
into the engine.


Bill M.

Was the flywheel and bendix rusted?

Was the bendix replaced recently (last couple of seasons)
because it was rusted and fell apart?

Does the ski have a fuel primer?

Was there any rust or pitting on the crank nose where the
main seal rides?

 

[yamanube]

@wmazz The ski had an improperly installed flywheel o ring, the front crank seal was leaking and had rust from the snout to the front web face. It also had a leaking head o ring and was injesting water there. Both cylinders had debris run through them with pitted pistons and domes. The bendix is headed to the bin as well. It's a full rebuild, I advised a new set of cases but again, the owner obviously would like to keep the porting work.
I have never measured the crank bore, nor installed it with loctite and have never personally had this happen. I am not likely going to start either to be honest.
Funny enough, the engine builder was adamant about "gluing" everything with 1211 to fully seal up the engine from saltwater, and it leaked in multiple places. All the 1211 did was make it more difficult to tear down.

 

[Myself]

I've seen SEVERAL cases like this. The 65u 1200 seems prone to it. Clean everything, lap the case halves as Kevbo suggested, also clean the new crank bearings with brake parts cleaner. Seal up the case halves with case sealant AND at the same time, smear the sealant in the bearing grooves. Bolt it all together and don't touch it for a day. It will all set up nice and the new bearings will stay put, end of story.

 

[Half flip95]

That's the worst chatter I have seen (fretting?). Buried in an old thread on here, I think chuckie had mentioned putting a dab of 1211 (or loctite?) where the bearing meets the case to keep it from moving around. I did it on a set of cases that had the pins pushed out to make sure the oil holes stayed lined up.

I wouldn't run that as is, unless its going into a beater ski.

 

[WFO Speedracer]

We had the same case chatter problem on the 1986 and
up 650's to about 1991. I was under the opinion that these
cranks, were not strong cranks and just flexed too much.

I suspect the main bearings had some rust damage that
contributed to the bearing failures.

Look at the old front main seal. Does it have a loose or
worn out fit on the crank? Worn out front main seals
allow all kinds of garbage to get sucked into the front main
bearings.

Often front main seals wear out first on the vacuum side
(The flywheel side), and that allows the junk to be sucked
into the engine.


Bill M.

Was the flywheel and bendix rusted?

Was the bendix replaced recently (last couple of seasons)
because it was rusted and fell apart?

Does the ski have a fuel primer?

Was there any rust or pitting on the crank nose where the
main seal rides?

Kawasakis fix for this other than the redesign on the cases and crankshaft was to use a thin coat of red loctite on the bearing during reassembly.

 

[BruceSki]

Loctite makes something specifically for this. I’ve fixed electric 15HP drive motors for chilled water pumps at work that had sloppy bores for the OD of the outboard bearings on motor. The motor to the right of the red one is one I fixed with that bearing retainer compound.

It’s a cheap fix for old clapped out stuff. We finally got the $$$ to replace 1 pump and motor out of a set of 3 in each of the 20 buildings we service. Now they will run until failure like everything else does

 

[Sparkplug]

Loctite makes something specifically for this. I’ve fixed electric 15HP drive motors for chilled water pumps at work that had sloppy bores for the OD of the outboard bearings on motor. The motor to the right of the red one is one I fixed with that bearing retainer compound.

It’s a cheap fix for old clapped out stuff. We finally got the $$$ to replace 1 pump and motor out of a set of 3 in each of the 20 buildings we service. Now they will run until failure like everything else does

God I don't miss working in poopholes like that during shutdowns. Doing the stuff the plants own millwrights didn't wanna do.

Spec for us was 3 threads minimum tho. Boss saw some jank shiat like mis matched bolts on a flange. You'd get a walk to the door.

Loctite green is running the world. You wouldn't believe what it can do. Just imagine what the Taiwanese guys are making work.

 

[BruceSki]

God I don't miss working in poopholes like that during shutdowns. Doing the stuff the plants own millwrights didn't wanna do.

Spec for us was 3 threads minimum tho. Boss saw some jank shiat like mis matched bolts on a flange. You'd get a walk to the door.

Loctite green is running the world. You wouldn't believe what it can do. Just imagine what the Taiwanese guys are making work.

I ask the boss to order 1000 bolts, I get 750, 500 are the right size. Half the time it’s the purchasing department finding “a cheaper bolt”. Gotta make due with what we’ve got. Just pretend you’re working during the Great Depression, then put on my uniform.

As long as I make it not leak and pump water or steam through it, it passes as good for the next 20 years. I posted that pic on a stationary engineering page and the guys bitched the bolts were too long .

They keep my check coming every Friday and I do as I’m told, fix what I can on a shoestring budget.