Crankshaft questions a Ulis

[andrew handley]

Hi All,

Just looking at my R69s engine and hoping for some advice please?

The crank was rebuilt here in the UK by someone who was referred by a couple of people with good knowledge of BMW /2 engines. It was put together using NOS parts (rods, big ends and bearings).

Having run the bike for 500 miles the oil seems very dirty as it did when I changed it at 300 miles. There is some metal present, both very small and a few slightly bigger sand grain size. Oil analysis said all in spec but added a comment about only relating to microscopic. The bike runs really well having been fitted with all new bearings, first oversize pistons and 2 new top ends. Only concern is oil condition and presence of metal.

Having looked in some detail today I'm struggling to find challenges aside from:

- measuring runout right on the front of the crank gives approx 0.04mm runout so in spec.
- Con rod end float appears over spec at 0.2mm although not sure if I've measured properly (wobble rod and insert a feeler into the gap.

So, questions if I can:

- how much metal, if any, would I expect in the first 1000 miles.
- How do I measure the rod end float and is over spec that much of an issue?
- Should the oil holes in the crank pin bungs point straight down or is somewhere hear good enough?
- Are Uli's refurb cranks any good assuming I need another one?
- How many times can the mains be pulled without damaging the seats?

A lot of questions I know but hoping someone with experience and knowledge can set me straight before I go do a load more work and spend more money.

[caker]

Hi,

Is the stuff you're seeing in the oil ferrous metal (magnetic) or alu, or ?

Was the case sand blasted? If not properly cleaned out the blasting media (sand, glass beads, oxides, etc) can stick to the casting and then come back out after rebuild, and ruin your engine.

I would expect very little stuff in the oil.

If the connecting rods have ANY *radial* float (in and out), it's already too far gone.

It looks like 0.20mm can be ok for big end axial clearance? Disclaimer: I am not a crank rebuilder But, read this from Salis' website:

Use a feeler gauge to set the axial play to a value between 0,07 and 0,10 mm. This is the original factory specification, However, nowadays some experts set the conrod axial play to 0.20 – 0.25 mm: this is to prevent the big end of the connecting rod from rubbing against the inside of the crank web due to the bending of the crankshaft under high load.

Not sure what you mean about "mains", but I would NOT expect the bearing carriers front and back and the crank journals to be harmed during removal and installation, when done correctly.

-Chris

[andrew handley]

Thanks Chris - had forgotten about that video which answers my question in the most part.

By Mains I mean main bearings so your reply covered it.

[Slash2rider]

Hi
Do you have any scratches on cylinder bores?
After rebuild most running in metal is in the oil after 20 miles so if first change is after 300miles there will be a lot but if you clean the oil pan after 300 miles and there is still as much metal after next say 500 miles you have problem .There will always be some metal shinning in the oil as long as you can't feel any grit when smearing residue from oil pan between fingersit should be Ok.Are grains you found metallic?I found it almost impossible to clean the engine after media blasting but oil testing should show glass or other media?How many magnets can you fit in oil pan

[Flx48]

Hi Andrew-
To add to the comments from Chris and Slash, since we're not there to see/feel your oil, we only have your description with which to speculate/opinionate.

Oil's primary job is lubricating, followed by cleaning, cooling, and sealing.

I use detergent oil, and expect with every oil change, to find the oil to appear dirty.
Fresh oil will turn dark in color within a few miles, from honey colored to black.
The color change is the result of the detergent picking up the combustion byproducts that have entered the crankcase.
And since our engines have no oil filter per se, the oil is the filter, as the dispersant keeps the debris in suspension within the oil.
Which is why these engines need very frequent oil changes, otherwise the oil slingers become debris reservoirs by default.

During break-in, most of the metal debris accumulated is from the new rings wearing into the new honing on the cylinder walls.

Bear in mind: in an engine with an actual oil filter most of the break-in debris is captured by the oil filter, and so can only be viewed by cutting the filter open to inspect.
Whereas with a /2 engine we get to "view the sausage being made" during the oil change, as the filter is, in effect, already cut open.
Best-
George

[808Airhead]

If oil is getting black soon, you have poor ring seal/ rich mixture washing the rings. I went through this …attention to ring gaps and valve sealing is essential. Blowby and poor valve sealing will cause oil to turn black quickly.

[andrew handley]

Thanks everyone and apologies for taking a while to respond... I've been away working so haven't had much time available.

I might be worrying for no reason here but after having a push rod break and grind itself to pieces on my R27 I'm keen to get ahead of any problems this time.

I stripped it down to just the crank and cam left in the block today and can't find any obvious faults so will pull the crank out and see what's there.

I'll measure the crank again and see what I find. The pistons were new into rebored cylinders so that could account for some of the metal and I had new valves, guides, springs fitted in the top end along with one new rocker and some new rocker rollers. Ring gaps were set carefully so don't think it's that but will check again. The oil doesn't have a sandy feeling but there are a few larger bits in the rocker covers and a rare earth magnet in the sump does move some dark particles when I move it through the oil (which I thinned with some break cleaner to get a better view.

Thoughts and insights really appreciated!

[jeffreestar]

Given the complexity of these issues and the importance of engine reliability and performance, consulting with experienced BMW /2 mechanics or forums dedicated to vintage BMW motorcycles could provide valuable insights and guidance specific to your situation.
fnaf

[808Airhead]

In the process at the moment of breaking in a 58’ R69. I changed the oil at 50 miles, 100 miles,300 miles, now at 580 miles on break in. With a magnetic drain plug the swarf is getting less and less and the oil remains clearer longer, and there is less oil consumption, so breaking in nicely. The swarf, as long as it is very fine is OK and normal. As everything beds in the engines just get better. Enjoying the ride!

[vechorik1373]

When I built engines for customers, (and in ALL of my personal machines) I placed a LARGE rare earth, POWERFUL nickel plated magnet in the steel pan. They stick to the steel pan, and will magnetize a large area surrounding the magnet.
There is no fear or possibility of the magnet to move, I promise. If you dislodge one, you have killed yourself in a head on crash! You may find this incredible, but more than once, I have returned from a ride, and noticed a steel wood screw, that was kicked up by the front tire, and was stuck to the outside of the pan! As part of regular maintenance, after the break in, one should remove the pan, and clean the pan and the magnet. The tiny drain plug magnet, while it helps, is totally inadequate. If you are running an deep sump aluminum pan, simply place the rare earth magnet on the top of the steel oil pickup screen. Then when you do drop the pan, you can pull the oil pickup screen, slide the magnet off and clean all the hair off of it. Don't forget to thoroughly wash out the pick up after the magnet has been removed, using spray carb cleaner, to get all the metal particles washed out of the inside of the pick up.

This is the link as to where you can order these magnets.
https://www.kjmagnetics.com/

This is one I always used, and sold when I had bench mark works.
BY0X02SH
2" x 1" x 1/8" thick
Nickel Plated