Tooth wear and oil pump rotor

[Soeren]

I'v been working my way into the clutch husing, to have a look at the rear main seal and oil pump o-ring.

What is your take on the flywheel tooth wear? Is it ok to use?

And what's up with the two grooves on the innter rotor, I havent seen them on any other rotor. If it was wear wouldent the grooves be present the whole way around on the rotor?

Last pictures in the Google album: https://photos.app.goo.gl/CAA8aJdgayJrNNdX8

[Tony Smith]

Your starter is striking the ring gear will it is not rotating. I would service the bendix and possibly replace the pull in solenoid depending on how much crud I found in the bendix. It is most likely that servicing the bendix will cure th  problem. The ring gear is fit for further service, besides I see you have a kick start gearbox anyway :-).

Your clutch driving plate is toast with that much concave wear on it, if you put a new clutch plate in it will have a reduced contact area and probably slip. I would buy a serviceable 2nd hand one - in fact if I could buy a clutch carrier and complete clutch pack in good condition for a reasonable price I would replace the lot with a new clutch plate.

Your oil pump is a bit disturbing, at some time something hard has gone through there. If you know the oil pressure before you started work and it was OK, you could maybe choose to reuse it, but for the relatively low cost of an oil pump, opposed to the time it takes to get to it, I'd replace it with a new one.

I see you are about to fit an 860cc kit. May I ask what the mileage on your bike is? Given the oil pump I'd want to have a look at the bearings before subjecting them to the load increase of the 860 kit. The rod bolts are cheap enough - I'd pull the crank and inspect all bearings. If the bearings measure even slightly worn, providing everything is still round and after polishing is still within spec I'd put it back together with new bearings.

On the other hand, if the bearings look and measure OK don;t be afraid to put it back together with the same bearings - two sets of rod bolts are a cheap investment to know how good or bad your bottom end is.

Whilst the rods are out, check the small end bushes against the new wrist pins - the slightest movement/rock is ground to replace the small end bushes.

I have to say that my very strong suspicion of the cause of many unhappy outcomes with big-bore kits is fitting them to a well worn bottom end. You are increasing the capacity to 132% of original.


Lastly, your heads - pull the valves and check the guides - new guides or k-lines according to your preference. if the bike has more than 50,000km on it I would shout it new exhaust valves and collets, and preferably also new inlet valves and a full set of springs. If you want to reuse your old springs - here's a tip using some oversized body washers and a length of threaded rod, thread all 4 of your valves onto the rod with washers between each spring. Then use a pair of nuts to tension the springs until at least one is approaching coil bind. If the springs are not all equally compressed - chuck the lot and replace with new. OTOH, if they are equally compressed, they are probably OK to reuse.

I could go on and on but I will simply make the point again that you should not fit an 860 kit to a worn and tired bottom end, self destruction awaits those that do.

[Soeren]

Thanks a bunch Tony, that is a very usefull reply. Ill start looking at the bendix right away. And I'm happy the flywheel has some more miles in it

I was acctually about to buy a new clutch all together, from motobins. But I guess a used one with minimal wear would suffice.


As far as I know the oil pressure was ok, at least the oil pressure light indicated that it was fine. But what the actual oil pressure was I dont know. When you say new oil pump, is that a new outer and inner rotor plus a new cover, or does it involve additional parts?


I haven't had the rods out, but they rotate freely with no notecable rod play, and seem to be at good health. But I'll pull 'em out if you strongly advice to.

Followers and cam, have no pitting and look good.


And my heads where rebuild two years ago, new seats, new valves, new springs, new guides and new cups/caps/cotters. Everything is tip top

[Tony Smith]

When you say new oil pump, is that a new outer and inner rotor plus a new cover, or does it involve additional parts?

Providing the housing is not badly scored, inner and out rotor and new cover will suffice. If the housing is badly scored the only cure (that I know if) is to have the block machined so that a new steel housing can be pressed in - that is expensive.

I haven't had the rods out, but they rotate freely with no notecable rod play, and seem to be at good health. But I'll pull 'em out if you strongly advice to.

It's your call. You didn't say the mileage on the bottom end. Me, I'd pull the crank and mic it for both size and ovality, if it checked out OK, I'd have it polished and put it back with new bearings.

The BMW is a strong and long lived bottom end - but you know that stuff that scored up your oil pump - you know where that went next.

[Soeren]

Finaly got around to have a look at the bendix gear and take a picture of the oil pump housing.

Housing looks like this: https://photos.app.goo.gl/LRMCK86VtkRjTYRDA


The bendix gear looks alright to me, but the windings have a groove worn into them, I suspect this is not normal?: https://photos.app.goo.gl/t2JqKERPuZ4XuTRM9

[Tony Smith]

I'd use that pump - new gears and cover though.

The bendix is *just* fit for further duty and it looks utterly dry. Starburaghs paste is good on them, otherwise really heavy axle grease - sparingly. The field windings are obviously not shorting - yet. Your nearest bunnings will sell Spar Varnish in small cans. Clean and degrease the rotor and give it a birthday with spar varnish over any damaged portions, that will at least provide insulation. Be careful with the varnish though , it does build up and could easily decrease the distance to the field coils.

I'd shout the starter motor a new pair of bushes (buy from an auto electrician) if the old ones are worn and have any significant movement - axle grease i there too.

[Soeren]

Snapped a few quick pictures of the connecting rod bearings: https://photos.app.goo.gl/uUgwu7vGT51RjXzz8

They dont look too bad. I guess one small piece of debris went through one of the halves, and there are some dark spots (what are they?).

Use or replace?

[Tony Smith]

Replace.

The cost of a set of bearing inserts is fairly trivial.
There are two big questions to be answered before slapping new bearing inserts in and buttoning up.

1/. Using a micrometer, measure the big ends. Whilst I fully expect the size to be within range, I would check the ovality as this is a sign of an impending problem.

2/. One of the problems you can have if you replace only the big end bearings is that you can, in some circumstances, have difficulty in maintaining oil film to the bearing as if the mains are worn the oil will flow out through them and not through the big ends. Happily if is pretty rare and if the inserts you have removed are well within wear limits you will not have a problem with new ones.


Did you measure the cold/hot oil pressure before pulling it apart? Oil pressure can tell you a lot about the internal health of an engine.

The dark spots are a bit interesting - they are not wear, they are the remnants of the lead coating applied to the insert shells to assist with running in. That it is still there is a sign that there is a few microns out of round in the insert shells when installed. I would not worry about it.

Aside from the witness mark were a piece of cr@p went through the bearing, those inserts are in fine condition, but on principle I tend not to reuse inserts (although ?i did just that with the mains on my own R65 when I rebuilt it, but then I knew it had done less than 60,000km and they measured so close to perfect I doubt that new ones would have fitted any better). I would however still replace the big end bearings because they work so hard.

[Soeren]

New bearings it is.

Ovality seems good aka not pressent.

And no, I didnt meassure oil pressure before pulling it apart, I just know the oil preassure was good enough to make the oil light turn off.

A new minor problem has come up. When I pulled one rod, I had a hard time getting the two halves apart. It turns out one of the guide pins is slightly bend and makes it a hasstle to get the two parts to fit together, or go apart, without a lot of force.

Can I fix the pin, or should I get a new rod?

[Tony Smith]

Can I fix the pin, or should I get a new rod?

Out of curiosity, was the rod with the bent pin the one with the lead coating still visible on the insert shell? If so we have an answer to the "why?" question.

The purists will lynch me for this, but unless you can find a rod very cheap I would carefully reuse the one with the bent pin - love to know how that happened but I'd suspect that the Romanian guest worker dropped it on a Monday morning after a hard weekend on the turps. Don't try and straighten the pin, just put it back together carefully. Use new big end bolts of course - there are many people who say it is OK to reuse them, the much revered Snowbum included, and I must say I don't always follow BMW's edicts on whether or not to reuse bolts myself. BUT, the two places I will never, ever, reuse a bolt is the gearbox output flange and conrods. The reason is simply that over the years I have had a failure of the flange bolts on my own bike and (worse) failure of conrod bolts on an engine I helped put back together. I looked carefully at those bolts and measured them for length against a brand new one and said "I reckon it's ok to reuse them". Approx 20k km  later half the rod exited the block immediately above the RHS cylinder.

So, I use new bolts cause I reckon they are cheap compared to the alternative.