R60/5 rebuild nears completion – with some puzzles. . .

[Tin Woodman]

Managed to get a few things accomplished yesterday before a bunch of buddies showed up. Lapped the valves/seats. Hadn't done it in years and had forgotten how satisfying it is -



Was going to improvise method of inserting main seal but after much research, particularly one of the old threads on this forum, decided to borrow a tool from a local inmate. Questions remain - install wet or dry, is this the most current design, should it be driven all the way home?

[Plaka]

Originally Posted by Tin Woodman

Managed to get a few things accomplished yesterday before a bunch of buddies showed up. Lapped the valves/seats. Hadn't done it in years and had forgotten how satisfying it is -



Was going to improvise method of inserting main seal but after much research, particularly one of the old threads on this forum, decided to borrow a tool from a local inmate. Questions remain - install wet or dry, is this the most current design, should it be driven all the way home?

Examine the crank for wear. If it has grooves in it from the old seal it's nice to get the new seal lips running on fresh metal. The seal gets fully seated so to move it out a skinch requires some shims.

Just a bit of lube on the outside to get it in. Full on assembly lube on the inside however where it contacts the shaft. When you first fire the bike, you want it lubed on the shaft from the very first instant.

Valve looks ok. Did you mic. the shaft? Any signs of blowby at the guide? (lot of dark residue on that side of the head by the rocker arms).

[Tin Woodman]

Plaka, flywheel mating surface has polished line but no ridge -



I'm assuming the new seal contacts a different part of the surface anyway.

Yes, mic'd valve stems and guides and they are within spec. So far I'm getting off lucky.

[Plaka]

Originally Posted by Tin Woodman

Plaka, flywheel mating surface has polished line but no ridge -



I'm assuming the new seal contacts a different part of the surface anyway.

Yes, mic'd valve stems and guides and they are within spec. So far I'm getting off lucky.

Beautious. Skip the pizza tonight and get a tube of honest-to-gawd assembly lube with plenty of moly and other goodness in it. Goes on the shaft prior to the seal, the valve stems, the rocker bearings and valve stem contact surfaces, the pushrod tips, the lifter faces and bores, big end bearings if apart, etc.

Before you build the heads go in the sink and get scrubbed with hot water, a brush and dish soap. Though shalt have no particle of valve lapping compound anywere on your parts, your body or the nice towels you use to clean up. If the ol' lady bitches get a new ol' lady.

Understand the seal is supposed to weep. if there isn't an oil film between the shaft and the seal the seal will wear rapidly. The difference between "weeping" and "leaking" is "leaking" washes the dirt off . The ideal surface for the seal to run on has a very slight texture. It is difficult to achieve and I wouldn't screw with it. The seal bore needs to be perfect. Any dings get dressed out.

[Lornce]

Originally Posted by Tin Woodman

Tonight's discoveries were straightforward. Rear seal actually pulled out easily. I wonder what left the bright mark on the flywheel mating surface? Is this normal? Not a ridge, just a highly polished line.



Teeth on the flywheel looked fine until I took this close up photo. Looks like the Bendix has chewed up the teeth a little - is this flywheel toast?



Cylinders are perfect with exception of course of the pitting on the left one. Pistons seem to be in spec - can still see the original machining on the piston walls. These are the original pistons (or rather, they have the markings of the original ones of 73.47 B), I'm a little mystified - the hone marks look fresh in the cylinder barrels. The ring end gaps are way out of specification - almost like the last mechanic mixed up metric and standard measurements.Or do the rings just wear like this? This would possibly explain oily buildup on exhaust.



Observations?

This has been interesting: Had no idea the cam was in two parts - and I've seen a few broken cam ends repaired with a tapped hole and an allen bolt.

Haven't read the entire thread (I'm not retired) but just a few thoughts on your top end re & re and questions and points you've raised.

Unleaded fuel: It's a non-issue. Don't give it another thought. But I'd properly resurface those valve faces and seats before reassembly, if I were you. The problem with haveing this done professionally is that most shops will hog too much material off the valves and out of the seats when just a gentle kiss is generally all that's required. See if you can find a guy who does aircooled Porsche heads or the like and express your concerns.

Cylinders and Pistons: R60's don't make enough power/heat relative to their cooling surfaces to wear themselves out. A bit of an overstatement, but generally true for the bores compared to 750 and larger airhead cylinders. ie: A rebore might be a little over the top for this situation. Bet you a donut a good, modern, three piece oil ring would render that pitted cylinder fully functional. (Hastings makes a cast ring set with a modern three piece oil ring for a Renault 4cyl motor that's a direct replacement for the R60 airhead motor. I've reworked several R60's with these rings with excellent long term, high-mile results). Failing that, good used R60 top ends used to be fairly easy to find with all the enthusiasm for "bigger is better" type thinking that goes on in the motorcycle world. I'd be looking into those options before going the rebore route.

Camshaft: Looks like it's too late, but I'd have taken the opportunity to go with a good used 308 degree cam from a 750 or 900 motor.

Look forward to reading the rest of the thread as time allows. Very interesting discussions going on here.

[disston]

Originally Posted by Tin Woodman

Observations?

Some install the rings that BMW sells even when they show this defect. BMW apparently doesn't consider it a problem.

Some buy the next size up and grind the ends to get the correct gap. The problem with this is (or may be) that the curve of the larger ring doesn't match the cylinder curve very well. Maybe it wears in or maybe it's not an issue but it does seem to be not right to me.

Some use after market rings which may have different profiles or may be different in some dimension (thickness or width being compromised to get the correct ring gap?)

These are the solutions I've heard others mention. I don't know which one works the best. Or at all for that mater.

When I had this problem in my R90 I bought a new pair of pistons because they came with new rings. And those rings fit correctly. Turned out the new pistons were also an improvement over my worn out old pistons (which I was originally in denial about)

My solution was not the cheapest but I had the money in those days. Money is a lot tighter than it was 5 or 6 years ago and it's more difficult to justify throwing a lot of it at my problems.

If I had to chose today I think I would go with the OEM new rings and the too large a ring gap. I would keep and eye on compression and also talk on the forums for the day that riders say it no longer is a problem. I totally expect that to happen some day and then all of us will buy a new set of rings.

[Tin Woodman]

Wow, fellas - that's a lot of data to digest. You probably all know by now I take your suggestions very seriously. Plaka, I actually run a lot of my parts through the dishwasher including the heads - my wife actually approves! Thanks for reminding me of the assembly lube - I was using ordinary motor oil. Good point. Picked up some today.

Lornce, welcome to my little project and thank you for your comments - finally got a definitive opinion about unleaded gas. Will check out the oil ring issue and thanks for the suggestion. Cheers.

Bill and Charlie, keep the comments coming - this project has suddenly become very interesting. I wish I had found this forum years ago - hell, maybe I'd be finished by now.

[Bill Harris]

I wish I had found this forum years ago - hell, maybe I'd be finished by now.

What? We keep sending you off on these little side-trips.

But seriously, you have made a lot of progress the past few weeks.

--Bill

[supershaft]

Originally Posted by Tin Woodman

Managed to get a few things accomplished yesterday before a bunch of buddies showed up. Lapped the valves/seats. Hadn't done it in years and had forgotten how satisfying it is -



Was going to improvise method of inserting main seal but after much research, particularly one of the old threads on this forum, decided to borrow a tool from a local inmate. Questions remain - install wet or dry, is this the most current design, should it be driven all the way home?

You got that RMS at a BMW dealer? I didn't realize you could still get the earlier type? Do not use that seal. The newer type works SO much better. Either type should not leak or weep at all. The later type seal is much more likely to get you to that goal. Chamfer the seal boss with an exacto blade. Put motor oil on the outside of the seal. Install the later type with no oil on the inner seal.

I think running standard size rings work better than oversize despite the large gaps. Less tension and friction too.

That engine might of ran a little and sounded OK but those bores are way past really running. It is going to USE some oil! It needs a bore job IF those cylinders are not too far gone. It will be close if they aren't.

Install pistons and rings with no assembly oil. I wouldn't oil the valve stems either. Valves/guides don't need or want oil. All it will do is make your bike smoke like a mofo on start up instantly oiling your top end that hopefully should remain dry for a few strokes to better seat in the rings.

[disston]

This is the modern rear main oil seal. Part #11 11 1 338 342



Notice it is mostly black, the inner lip is a kinda brown. This seal has a lip made with Teflon. You should form the lip of the seal with your finger before installation, check the fit against the part it fits, either spacer or flywheel. It is installed with the lip of the seal dry. The outer edge may have a little oil applied to aid installation.

It should be installed with the proper tool and not beat in with hammer and block of wood.

It is not made like the old seals. This info may seem strange but it is correct. Dry.

[supershaft]

Originally Posted by disston

This is the modern rear main oil seal. Part #11 11 1 338 342



Notice it is mostly black, the inner lip is a kinda brown. This seal has a lip made with Teflon. You should form the lip of the seal with your finger before installation, check the fit against the part it fits, either spacer or flywheel. It is installed with the lip of the seal dry. The outer edge may have a little oil applied to aid installation.

It should be installed with the proper tool and not beat in with hammer and block of wood.

It is not made like the old seals. This info may seem strange but it is correct. Dry.

I have had good luck installing them per a later service bulletin. Dry seal with no preforming. I have installed a lot of them thusly with never a problem. Lightly oil the OD.

[Tin Woodman]

I knew that photo of the seal would stir up controversy - no, I didn't get it from a BMW dealership. Clearly it is old stock and I suspected as much. Definitely will get a modern one this time. I've come this far, might as well do it right.

SS, I see what you mean about using the seal insertion tool as an extractor. Those sheet metal screws would cause damage if screwed in indiscriminately. Looks like a great tool for installation, though -



Reinstalled valves last night before reading the last few posts - too late to un-lube the stems. It doesn't help that the shop manual insists they be lubed. BTW, the manual is often vague and ambiguous and glosses over key points. Also, it would be great if there was a glossary!

[Plaka]

Originally Posted by Tin Woodman

I knew that photo of the seal would stir up controversy - no, I didn't get it from a BMW dealership. Clearly it is old stock and I suspected as much. Definitely will get a modern one this time. I've come this far, might as well do it right.

SS, I see what you mean about using the seal insertion tool as an extractor. Those sheet metal screws would cause damage if screwed in indiscriminately. Looks like a great tool for installation, though -



Reinstalled valves last night before reading the last few posts - too late to un-lube the stems. It doesn't help that the shop manual insists they be lubed. BTW, the manual is often vague and ambiguous and glosses over key points. Also, it would be great if there was a glossary!

The manual says to lube the stems because that is a pretty standard way to do it. If you follow SS's posts you will note he often has his own way of doing things and it's often at odds with the rest of the world. Not saying that's a bad thing but it's well worth being aware of.

The guides are oil impregnated. Then they get oiled plenty from above---once the oil pressure is up. You can get guides with a teflon scraper on top intended to minimize oil leakage down the stem.

If the seal you get has installation instructions, follow them.

putting the rings in "dry" is one method and has it's proponents. There are a number of others. if you want to see a real Fords 'n' Chevies pissing match watch the various camps go at it. I use the "wet" method. Some oil in the combustion chamber is trivial. Do a wet compression test and you get a Lot of oil in the chamber, like a tablespoon or more. Don't hurt nutin'. Might need to clean a plug but other wise it just burns off. Some vigorous riding helps. These pistons and heads have seen multiple wet compression checks in the months before I tore it down:






I have found, as a general rule, that when there are several camps on some issue, and the battle year after year after year about who's right, then it doesn't make a hoot bit of difference. Any of the methods will return good results. This is of course the last thing anyone in any camp wants to hear, they are invested in "rightness". So if you don't want to alienate anybody, keep your mouth shut.

When I build a motor or gearbox I customarily use assembly lube anywhere a part gets lubrication in service.

As far as dynamic seals, yeah, they all weep. They have to. It's also a physical impossibility to prevent it. Think about what happens when you oil a shaft before installing a seal. As you slide the seal on it wipes away all the oil it can. Any oil left between the lip and the shaft represents the gap between the seal and the shaft. if there is no gap then ALL the oil will be wiped away and you have effectively installed the seal dry---except for some oil on the inside of the seal. Gonna be a lot more oil on the inside of the seal as soon as you fill and start the motor so that's moot. I think you'll find it is quite impossible to slide a seal on an oiled shaft and have it wipe the shaft dry.

I've tangled with some problems where I wanted a seal on a rotating shaft where these was oil on one side of the seal and thick glue on the other. No oil could pass the seal to contaminate the glue. After talking to a number of seal suppliers I was finally convinced that it could not be done. I ended up going with a sealless design.

[disston]

Originally Posted by supershaft

I have had good luck installing them per a later service bulletin. Dry seal with no preforming. I have installed a lot of them thusly with never a problem. Lightly oil the OD.

I have no problem with that. The shaft or in this case the flywheel will form the seal as it is installed.

[Tin Woodman]

Originally Posted by Plaka

I have found, as a general rule, that when there are several camps on some issue, and the battle year after year after year about who's right, then it doesn't make a hoot bit of difference. Any of the methods will return good results. This is of course the last thing anyone in any camp wants to hear, they are invested in "rightness". So if you don't want to alienate anybody, keep your mouth shut..

Yes, I have seen a few dust ups on other historical threads - some of you guys are pretty passionate about your beliefs. Makes for interesting reading but more importantly, it challenges conventional wisdom and helps define best practices. Syncs up nicely with my philosophy of questioning everything until the ambiguity disappears.

Thanks Charlie for your precision on digging up the part number on that seal - my supplier will exchange it this week. No, I was never going to hammer it in with a block of wood but I confess I thought about it.