Not another big end bearing question?

[ezzywave]

New guy here. I was given a basket case '99TLR. The motor was approx. 90% torn apart. When I got the connecting rods off I found out why it was "given" to me. The front piston's con-rod bearing wore out damaging the crank journal. After searching the forums I found this to be a rather common problem.

I measure it between .012" and .014". undersize. Of course it's out of round, and I'm measuring over the high spots. So the question is, how far undersize can it be ground? I want to use the "Honda bearing fix" that you guys have posted here, but I'm sure that the journal will end up at least .020" undersize. Is that too small? I'm not gonna race it, but it seems like a lot to have removed.

And just to be certain, are the Honda bearings the same O.D. as the TLR's? I mean, the big end of the rods don't have to be modified, do they?

Thanks for any help. This is the first 4 stroke engine (motorcycle) I've had apart, although I've rebuilt a dozen 2 stroke dirt bike engines in the last couple of years.

[The Ring-In]

The honda bearings are the same size OD however the rods will have copped a pounding so get them resized. the bearing shells nee the tang narrowing ( no big deal) and come in many undersizes.
Take the crank and rods to a crank grinder and get it crack tested first. then ground and then they will supply the bearings to suit. they usually can buy and supply cheaper than you can buy yourself .
they will understand what it is you are doing , so trust them to do it all.

so you need,
crack check
regrind
resize rods.

also the oil pump is now sus so most recommend a new one there.

[ezzywave]

Whoa! Are you in my garage I just got done looking at the inside of the oil pump and it looks like something ran thru it.

I will check the rods ends for roundness in the morning. Luckily I work in a machine shop so I can use the "good stuff".

Thanks for the advice!

Fred

[ezzywave]

Yep, sure enough the big ends of the rods are out of round. One of them is .0015" out and the other is .0045" out. The book shows a tolerance of .0002"! I'm bringing the crank and rods to the "best" grinder in town (Portland, Oregon) Monday morning, to get a quote.

Or... I found a place to buy a new crankshaft with new bearings and rods already assembled for $612.00. Plus a new oil pump, $90.00 and I'll be $700.00 into it.

I don't know... Maybe I should just part it out.

[The Ring-In]

Yep, sure enough the big ends of the rods are out of round. One of them is .0015" out and the other is .0045" out

I make this recommendation regularly and you are the first so far to follow thru and measure the rods. they actually look fine but as you've found they are out of round.

the ovality is sufficient to have a rod bearing with no clearance on two sides. it will seize rapidly .

I hope others read this and understand the need to check.

I hope you perservere with the motor, rods should be cheap enough to resize and a regrind is not expensive nor are aftermarket honda bearings.

on top of all that they are a lovley thing to own and ride.

[ezzywave]

The rod inspection actually told me a bunch of things besides the big ends being out of round.

The 'flat' area (faces? I call it the split-line) where the rod and the cap join together are not flat. A straight edge, accross the rod bolt holes, reveals that they are angled away from the center of rotation, as if there was enormous pressure trying to seperate the cap from the rod. Ahh, yeah, I guess that makes sense, since that's exactly what happened. And one of them, the real bad one, is kinda barfed up, I'm pretty sure that the kid who dissasembled it used a screwdriver to pry them apart. And, he broke one of the pins.

Also the diameter of the big ends, measured free, NOT clamped together, measured right at the split line, is very close to the book's spec. It is hard to measure, but I get .0001" or .0003" oversize.

Sooo, I wanted to remove the locating pins and grind .0030" off the rods and the caps split-lines, put the pins back in, reassemble and tighten the caps to the rods, and re-bore the big ends to the original spec. (I have access to a jig-bore machine at work) The re-bored area right next to the split-line might not clean up 100%, but it would be damn close! This way I could use the Honda bearings.

But I can't get the damn pins out.

Does any of this make sense? It sounds like youre a machinist too. Have you ever removed the pins?

I think I'm going to continue with this "project". I kinda like working with small parts. The casting I was machining today weighs 14,500lbs...

[The Ring-In]

Engine shops are set up for this job they have purpose built machines that do the job in legendary time and accuracy and usually for very little money .

I know we all love to do things ourselves but this is a send out jobby for sure.

Its called resizing and they do it to every engine when its reco-ed,

Replace the rod bolts too ...........

BTW I used to be an engine reconditioner. That's why this is so familiar to me