bearing question

[Loose Goose-Terry#1]

  NEVER replace only one insert bearing. Inserts come in sets for a reason...they are matched. If you replace only one insert and the remaining inserts have some time on them, then there will be a slightly closer fit and there is a real likelyhood that you could spin a bearing. Also, inserts have a "crush factor" so when installed and torqued properly, there is less possibility for the insert to spin in the journal.
Please, do yourself a favour and change all the inserts at the Same time and never re torque the same insert (even though the manufacturer may claim you can re torque the inserts up to three times). 

Terry A. Hume 

[Milwaukee Midget]

Another quick thought.  Any marks on the back of the insert or the aluminum?  Do they feel smooth?

[JimL]

Hi Jonny....noticed the pic of the bearing.  I've seen this kind of thing on cam-chain and cam-belt type engines (in cars, at least).  Usually fired up and revved/run hard before the oil pressure comes up.  Always on the "front" end of the crank.  If you bought a used engine/bike...well, now you probably know a little bit of its history.  Part of that condition can be promoted by oil choice (too thick....some cool guy using RACING stuff for the street) which makes the film build late on a cold engine that is treated badly.

This may mean the crank and block will prove to be straight, when you check it out.  Regarding "front main bearing" clearance; in Toyota-world, we often "select fit" one step tight on that bearing, to prevent crank thump when the modern "fuel efficiency" oil is fully heated, and the engine idles for long periods.  By the way, I don't mean "one step, as in .010"....it's more like .0005" difference.  In those cases, all bearings are replaced, but the front is selected "one step tighter".  We've been doing this since the early '90s and I've seen Lexus V6 run 300,000 miles with this fitting.

I don't know if the Hayabusa experiences that condition; I usually see it on "sequential throw" cranks, as opposed to "opposed throw" cranks (boy, that's a butchered up sentence!)  Anyway...my bet's on a mean former owner.

In the decades I was a line tech, I had a good friend worked next to me for many years.  He always said, "These cars want to run, people just won't let 'em!"

Regards, JimL

[bak189]

As noted by JimL, I have seen this bearing condition several times back in the "old days" on
Tri. and BSA triple (3 Cyl.) engines due (as noted by Jim) to reving the engine up before proper oil pressure was achieved. The trick was to kick the engine over about a halve dozen times (yes, that was in the days of kick-starters) with the ign. off
to get oil into the system.

[rebelce]

I thought you had to kick them over a half dozen times (or more) just to start them!    Well, at least in the 60's

[55chevr]

First you had to tickle the carb float bowls and get gas all over your hands, then you start kicking ... Joe