Parts sourcing - Top-End Rebuild?

[kmisterk]

HOLY CRAP!!!!
220 is WAAAY to rough!!!!
That's what caused all those deep scratches.
You should NEVER have used anything coarser than 600.
Then 1200 or 2000, and then polishing compound.

Hope you haven't scrapped it.
The idea is (was?) to polish it smooth, not to grind it down.

Whelp. I guess this is a tomorrow problem. I’ve tabled it for tonight.

It honestly felt like nothing was happening except I got the dirt and gunk off.

[gspd]

Whelp. I guess this is a tomorrow problem. I’ve tabled it for tonight.
It honestly felt like nothing was happening except I got the dirt and gunk off.

Don't give up on it yet.
Try smoothing it out a bit with some 600 grit.

[richard t]

‘80 r100t

Hey all.

Based on my Last Thread, I'm preparing for the potentially worst-case scenario in that I have to do at least a connecting rod bearing sleeve replacement job (and all seals/consumables along the way), and at worst a full crankshaft replacement and all that entails.

So my question is this:

My local dealership has what I presume to be OEM (or OEM replacement) bearing shells for 32.99 a piece. I'd need 4 of them.

Whereas, this pack has all 4 halves I'd need for less than half the full 4-set I'd need of the ones that the dealership is offering.

Should I not risk the potentially lackluster performance of the parts from ebay?

Furthermore, is there anywhere that sells a reputable "kit" that includes all the basic replacement parts and consumables you'd need to go through a job like this?

Also, any recommendations on things to watch for, common mistakes, etc? I've seen enough youtube videos (Boxer2Valve, Chris Harris), and have done a fair amount of research on some of the basic steps on getting to the crankshaft, and my plans are to not remove the pistons from the cylinders, instead electing to pull the wrist pin, as I don't want to have to deal with reinserting the pistons.

I'm nervous, and hopeful, that the *only* issue found is slipped connector rod bearings, and no extra damage. Fingers Crossed.

I worked as a mech for 49 years, I've never seen anybody sell 1/2 half of a bearing, that like selling each shoe by itself

[gspd]

I worked as a mech for 49 years, I've never seen anybody sell 1/2 half of a bearing, that like selling each shoe by itself

Most manufacturers do sell them in pairs.
BMW sells them individually, not sure why.

[Rob Frankham]

In fear of someone jumping down my throat and writing in BIG letters at me...

Why are you bothering with that crank. The journal is clearly beyond recovery without grinding and I doubt even a two stage regrind would get rid of all of the damage (and one thing I would agree with GSPD on is that regrinding is seldom a practical proposition on airhead crank)s.

Bite the bullet, get a replacement crank second hand... there are hundreds of them out there. You've already done half of the work in dismantling the engine and, in fact, it's perfectly possible (if a bit pointless) to replace the crank without taking the block out of the frame.

That crank is never going to be satisfactory... don't waste your time.

Rob

[gspd]

That crank is never going to be satisfactory... don't waste your time.

Satisfactory is a very subjective term.
Races have been won on way worse cranks than that, I've witnessed that firsthand.

There are a few used r65 cranks on ebay for under $200, so as Rob F suggested , that would make more practical sense.

It all depends on kmisterk's long term plans for this bike.

EDIT: Replacing the crank will require some special tools, some extra parts, and many more hours, and may be beyond kmisterk's scope of experience and budget.
Polishing the bad journal as smooth as possible and re-assembling everything is easy.
If the conrod big end is torqued down and there is no perceptible 'in & out' play, it will run well for tens of thousands of miles, in spite of the grooves. This would make the bike rideable and give kmisterk time to ride it around and decide what he wants to do with it in long run.

[Rob Frankham]

I would give that journal no more than 500 miles (and that's generous) before it's knocking again no matter how well it's polished... iof enough material is removed to make the surface smooth, I would be very surprised if it doesn't knock from the day it is put back together. It makes no sense to assmble the engine with a defective crank... even if K decides to get rid after the first ride, he will be more than repaid in the value of the bike and the experience of stripping the engine will be a good exercise in getting to know the bike. He's obviously not totally incompetent as an amateur wrench to get as far as he has.

Still, it's his decision, I can only advise from my own experience based on around 50 years of working with engines from steam locomotives to lawnmowers...

Rob

[gspd]

I can only advise from my own experience based on around 50 years of working with engines from steam locomotives to lawnmowers...

Technically 'by the book', you are 1000% correct.
BTW - I know nothing about steam locomotives and have no interest in lawn mowers beyond getting them to work well enough to cut the grass.

However, my almost 50 years of BMW and VW 'real world' experience makes me stick to my statement that "once the conrod big end is torqued down, IF there is no perceptible 'in & out' play, it will run well for many thousands of miles, in spite of the grooves.

[Rob Frankham]

I can only advise from my own experience based on around 50 years of working with engines from steam locomotives to lawnmowers...

Technically 'by the book', you are 1000% correct.
BTW - I know nothing about steam locomotives and have no interest in lawn mowers beyond getting them to work well enough to cut the grass.

However, my almost 50 years of BMW and VW 'real world' experience makes me stick to my statement that "once the conrod big end is torqued down, IF there is no perceptible 'in & out' play, it will run well for many thousands of miles, in spite of the grooves.

The principles of engineering are the same whether you are talking about a turboprop or a watch. Suffice it to say I wouldn't put that crank back in an engine unless it were absolutely the last chance and the lifespan of the machine was not important...

Rob

[gspd]

The principles of engineering are the same whether you are talking about a turboprop or a watch. Suffice it to say I wouldn't put that crank back in an engine unless it were absolutely the last chance and the lifespan of the machine was not important...

I'm not disputing what you are saying.
I wouldn't want that crank in my bike either.
That doesn't mean that it won't run well for a long while for kmisterk.

The principles of engineering remain the same long after the individual parts are worn way past their recommended limits.
Total destruction does not ensue instantly when the cylinder piston clearance reaches 'the book' published outer limits.
Tires don't self destruct when they reach the standard 2mm recommended wear limit.
And cranks don't stop spinning because they are grooved.
That's why there are literally millions of way past their prime old clunkers still on the road all over the world.
In their owner's minds, they still run great.
"she gets me to work and back everyday, she never let me down"
You actually see tons of them at BMW motorcycle rallies.
If 'book' specs trumped 'real world' specs, our roads would be empty.