Engine teardown poll

[trbig]

This may seem like a dumb question, but I want your opinion..

If you had the motor out of the bike and the cases split to fix the transmission among other things, would you replace the crank bearings while there, or simply put it back together and go with it since it hasn't had any problems there thus far in 40k miles.

In this scenario, imagine you are fairly strapped for cash and trying to do this as "Economically" as possible.

Tod

[bikerphil]

If they looked ok, I would leave 'em and put her all back together. They'll probably be good for another 40K. Maybe plastigage 'em? JMHO

[DGXSER]

Since we have already figured out I am ALMOST as much of a cheap@ss as Tod, I would surely throw it together as is. Now, that depends on how much money you have into the tear down to start with, as in, how much in gaskets and parts will it be if you have to repeat this in another 20-30K miles, versus how much for the bearings? IF brearings alone is all that is needed, and they cost less than the gaskets and possible machining if you spin one, then no brainer to change them out now.

This is a little more than I have gotten to yet, so I have no clue what that would cost.

[Big Daddy Funk]

If they looked good and plastigauged ok and I didn't have the cash to do it 100%, I would reinstall.

[rpgoerlich]

Plastigauge for sure while your in there. If they are within tolerance, put it back together.

[ccogswel]

Decisions Decisions

Man I hate these. 40k isn't nothing as I know a few members have over a 100k and counting but at the same time 40k is still alot. I guess I'd mic the crank to see where it's at and then I'd use some plastiguage to check clearence. If it was out more then a thousandths or two over stock then I would wait until I could afford the bearings. JMHO.

Now if this is a thing you need running quick then I'd throw them in and run it till you need to. Maybe if you decide to do a big bore kit then maybe then. If you haven't already had that done.

I'm in the same boat with my cage. I've been rebuilding my engine for a few months now. Only buying parts when I can afford it. Takes time, but atleast I won't have to worry about tearing back into for a long time.

[jetmechmarty]

Since you already have it apart, and don't have any money, I'd suggest giving up groceries for a few days so as not to leave it apart. Replace the bearings.

[The Lorax]

I was in that boat, actually I was fixing a broken shift fork, then found the spun main. the decision was pretty much made for me, that and I coincidentally got a disbursement from an old insurance policy, so I replaced cases and bearings and such, gears too. although, I think I did something wrong when I put it back together because I put those new fangled undercut gears from Yamaha in and after about 5k, I get the occasional skip in second gear (it is getting more regular) so at some point, I'll have to contend with that again. the good news is I still have all the old gears so I'll do the machine work on the gears and then swap them out....this time since I know about it now, I'll do the washer swap as well. it should be fun yee haw.

[fredintoon]

So are the bearings OK or not and have I heard of plastigage?
Am I the sort of unscrupulous person who'd put a suspect motor
back together and flog the bike to a stranger?
And how easy are main & rod-end shells to get anyway?
BTW, one thing I'd take a real hard look at with the engine apart is the oil pump.

[Shappers]

My bike only had 36k on it and the main bearings had all flaked and were 'rubbed'. It all depends on the history of the motor and how regular the oil changes have been.

I did a lot of work measuring everything with plastigage and came to the conclusion that all the different sizes are meaningless in the real world as the stamped sizes only relate to new parts. To get my 36k crank back in spec I just went with all the thickest shells (blue ones).

What you can do is buy a full set of shells for about $130 on ebay. Use all the Blue ones and then sell the rest of the box for half price to recoup some of your money. There are a lot of people who only go by the sizes on the crank and cases and would be happy to buy a complete set (albeit missing the blue ones)!!

[randy]

Tod, you've already had two motors eat crank bearings. Plastiguage them, at least!

[trbig]

Randy,

For once, this isn't my engine.. lol. It's just one I am helping with. I have an opinion on this, but that's irrelevant.. the motor and costs aren't mine. I was just wondering what the general consensus was.

I was told that I should have mentioned that the bearings look questionable to me with some ever-so-slight copper showing on a couple, but I wanted peoples' unbiased opinion on what they would generally do.


Tod

[randy]

Well, thank goodness it's not yours. Showing copper is not good. So, what is your opinion on this?

[trbig]

Well.. it looks as though I am in the minority so far on this one, but I also realize I have had more bearing and crank problems than the norm, so my opinion may be a bit biased.

Tod

[Wildkat]

But you're leaving the question way too generalized...

Am I going to replace the bearings just because I have my engine apart and they have a few miles on them? Well... probably not... unless I just happen to have the bearings on hand... Which... we usually do... but that's beside the point...
I replaced the bearings on my FJ when they probably could have gone a little longer... but I was in there and we had them on hand...

If they look questionable... then yeah... especially if there isn't a HUGE rush to get the bike on the road and I can wait to get the bearings (if we didn't have them)... beats having to take it all apart again... especially if it spins one during riding season...