Anybody ever blown the left crank bearing??

[mtuduc]

After a long ride home and then back to school (about 700 miles total) I started noticing some clicking and grinding from the engine of my m900. Looked through the timing window and noticed a wobbling flywheel. took the small cover off the end of the crank and noticed that the crank stabilizing bearing that's in the side cover was shot. All of the balls were on the bottom half of the bearing.

Today I got the cover off and found out the generator was grinding on the stator. The nut was still tight holding the generator and flywheel on. I took a screwdriver and used it like a visual dial indicator on the flywheel, and i'm pretty sure it was turning unevenly. Took the generator, flywheel, and all the gears off of the crank. I tried wiggling the crank and can't seem to get it to budge, so hopefully that means the left crank bearing is good.

Something must be warped or bent. I'll trouble shoot some more tomorrow. Has this happened to anybody? and if so, what ended up being the problem.

[clubhousemotorsports]

I have seen the bearing in the left cover fair on occasion, most of the time it appeared to be a bearing that had gotten debris in it of simply failed. I would measure runout on the crankshaft and see if you have any up and down movement from the main bearings. Good chance it may only be a bad alt cover bearing.

That said I had two 750's this year with failures of the left side main bearings. Both cases the crank floating cracked the alt cover, one was chunking the main bearing race.

measure things up and look real carefully.

[ducpainter]

raises hand...

mine was one of the cases ducvet mentioned.

[mtuduc]

If the main bearing was worn would I be able to feel some slop in the crank? Or how can I check the bearing? I doubt I'll be able to get a dial indicator until I'm home from school. Sounds like this might be a nice winter project.

[bigiain]

That said I had two 750's this year with failures of the left side main bearings. Both cases the crank floating cracked the alt cover, one was chunking the main bearing race.

Like this?

http://flickr.com/photos/bigiain/2238423424

I caught that before it did any damage to anything else...

big

[mtuduc]

Exactly like that, except there were four balls looking like that. That brown retainer had worn or just slipped further back on the crank and allowed the balls to all move to the bottom of the bearing.

Any word on what this pitting is from? Debris? Heat? Rust? I was thinking maybe rust because the previous owner let it sit a lot. 3000 miles in ten years.

[Duck-Stew]

I've replaced a few of those bearings.  Check the run-out as indicated and don't re-use the old nut.  Buy the Nichols replacement jamb nuts instead.  They are cheap insurance for $45.

[mtuduc]

While I'm doing all this is it worth the money to throw a nichols flywheel on

[ducpainter]

While I'm doing all this is it worth the money to throw a nichols flywheel on

It would be cheaper to throw a 900 in.   

[bigiain]

Any word on what this pitting is from? Debris? Heat? Rust? I was thinking maybe rust because the previous owner let it sit a lot. 3000 miles in ten years.

If that was your cause, it's different to mine - mine went at ~2.5 years and ~80,000km (~50k miles).

I've had running low on oil suggested as a cause (which I'm 99.999% sure is _not_ the cause on mine), I've also had someone I respect (Mike Soderland at Gowanlochs) say he's seen if occasionally, and he thinks it might be a manufacturing fault or metallurgy problem with the bearings.

I'm now over 200,000km on the replacement set, with no sign of the ominous rumbling noise that the first failure made...

big

[krista]

I've seen it once ... z!na's `95 900ss/cr did that.


click for my crankshaft runout page

You can buy those tools for under $40 if you're frugal. Runout usually means the crank is bent. Or on single phase models (pre98) the thin washer behind the starter gear / flywheel part is offset to the center. End float, or play along the shaft is more indicative of main bearing wear.

Personally, I'd remove the nut, check the washer (if a pre 98 model), put in new bearing and try running the engine. But I'm kinda strange...

Chris

[mtuduc]

Thanks Chris,

It's a 95. I've got the washer and I'm working on getting my hands on a micrometer to see if it has a consistent thickness. It looks like it has worn unevenly.

I would just go buy those tools, but I have access to my dad's tools once I'm home from college for the winter. I'll measure the throw then hopefully try a washer and bearing. The pisser is I finally got that cover to stop leaking oil. Definitely need to get the gasket from cacycleworks.

Is that a homemade crank turning tool?

-Brian

[krista]

Is that a homemade crank turning tool?

Hi Brian,

Thanks for writing back. No, actually, it's the one we sell. Anymore, I only "make" things when I can't find a version to buy. I'm too busy moving servers around and other IT crap to be doing much of anything lately!

Thanks,
Chris

[Bigbore4]

<snip>   I have access to my dad's tools once I'm home from college  <snip>

Assuming of course you put them away the last time you used them....

[ducpainter]

Assuming of course you put them away the last time you used them....

How you doin' dad?