Pushrod seal replacement...

[disco51]

I have the exhaust off right now as I was able to remove the exhaust nut (it came off with a dremel).  I've noticed a pushrod tube seal leak.  It's minor, but definitely notice a small drip pool on the ground since the bike has been parked for a good portion of the winter.

I've watched Chris Harris' movie on youtube, gone back through the archives, and looked over this article:
http://www.motorcycleclassics.com/mc-how-to/bmw-airhead-twin-pushrod-tube-seals.aspx

Looks fairly straightforward.  Anyone have any lessons learned tips?

How hard is it to get the piston in the cylinder?  I have no special tools and was going to use my hands.  I noticed Chris Harris used some piston compression thing.  

Any other things I should check out while I'm there?

THanks in advance.  Never done this and don't want to mess it up.

[steve hawkins]

Piston compression things are used because you actually need another pair of hands.  Although new piston rings can have sharp edges.

When Tony replaced the pushrod seals on my old/his R65 we actually found that the leak was coming from the cylinder to block interface, so we put some 'goo' in there when we closed it up.  Tony used my fingers to compress the rings whilst he gently pushed the cylinder back in place.

Seemed to work okay.

Rev light

[Luca]

I've never tried it, but there is an old trick out there that works if you have the clearance and no extra hands.

Pull the piston from the connecting rod and put it in the cylinder on your bench.  You want the piston as low as you can get it so that you can put the wrist pin back in as you're putting the cylinder on the engine.  Make sure to use a new wrist pin clip.

[Barry]

I've never use a ring compressor in my life and never broken a ring. With care you can easily do it with your hands especially if you adopt the method mentioned by Luca.

[georgesgiralt]

I too use my finger (and a large screwdriver with already used rings because they cut like a razor blades)

[Matt Chapter]

When I had that broken exhaust valve spring (!!!) I took the cylinder off to have it worked.. put it all back together just using my hands.  And some sockets to tighten it all up.  Crucial to note that I did not replace any rings.. if they were new I would have considered using a ring compressor a little harder.

Not saying that it's the easiest or smartest way, just that it can be done.  The pushrod seals are pretty easy, as long as they are aligned correctly.  I also used a little "goo" on the cylinder base.

Well worth the effort though, and certainly deserving of a cold beverage through the process and definitely after completion.

[montmil]

Yo, Disco!  Go down to the Resto Section and check "Relics Resto" thread. Some tips n' answers there you'll find helpful.

Besides the new pushrod tube seals, you'll need the cylinder-to-engine case O-rings plus a fresh head gasket and maybe a new rocker box gasket for each side. You are planning on doing all four of the tube tube seals, right? "Since I'm already there..."

You'll see a molded line on those new tube seal rubbers. That line goes down during install.

Check out Snowbum's site for an in-depth, lengthy and sleep-inducing article on replacing those hard n' leaky tube seals. Do tell me how it ends becaus... ZZZZZZ.

[Bob_W]

A large hose clamp will compress rings and only costs a few dollars and the biggest plus of all, the local auto parts or hardware has one in stock right now.
Bob

[Tony Smith]

A large hose clamp will compress rings and only costs a few
Bob

the smallish blade screwdriver you already own is even cheaper. Start the cylinder on the piston, when you get to the top ring back off a little bit. You will find that you are able to cock the piston over ever so slightly and start the ring into the bore using only your fingers. Whilst maintaining gentle pressure on the cylinder use your flat blade screwdriver slowly ease the ring into the bore. This is easier to do than it is to describe, but in very short order the ring will be fully into the bore - repeat two more times.
 
FWIW, the method above was taught to me by a guy who used to build racing Kawasaki and Suzuki engines, he could ease all four pistons into the bores quicker than I could set up 4 clip on ring compressors, drop the cylinders on and then take the compessors off again. I've used it ever since and whilst I actually do own a ring compressor that works on BMW twins, I've never used it

[Mike V]

I wouldn't bother with any sealant on the mating surfaces if you install a new large cylinder base O-ring. Just my personal preference.  Don't forget to renew the small stud O-rings.  Clean things up well. I use a little silicone grease on the outside of the pushrod tube seals and a little motor oil where they slide onto the pushrod tube (inside surface of the seal).  Here's a couple of pictures showing the pushrod tube seal alignment and the stud O-rings and the piston ring stagger.

I think it's prudent to reassemble with NEW base O-rings, stud O-rings, Pushrod Tube Seals, wrist pin circlips (if removing them)and Head Gaskets.  

I hate those freaking wristpin circlips!!!

[nhmaf]

Very good pics there, Mike, thanks for sharing!

I found it funny that our website code is still bleeping out the word "c o c k" from Tony's post - it has a habit of always assuming the worst things and bleeps out what it thinks is naughty..

[Ed Miller]

How many miles on those pistons, Mike?  Mine are kind of eroded, at about 94,000.  

[Mike V]

How many miles on those pistons, Mike?Mine are kind of eroded, at about 94,000.

They were young'ns when I did the top end Ed.  The bike only had about 12k miles on it when I obtained it.  But I decided to do the Top End (amongst other things) with upgraded valves, guides, and valve seats so I didn't have to look back.  Ted Porter did the head work who I'm very happy with.

[Ed Miller]

Thanks.  I had mine done at the Beemershop, too, so hopefully I won't need to see them again for a long time.

[jusgus]

My brother reinserted his piston from the bottom using his fingers to compress the rings. That was a 1975 R75. When I last had my jugs off I removed the wrist pin and reinserted the piston from the top with a ring compressor. The trick I learned was to use a heat gun to warm up the piston and the wrist pin will slip in or out with hand pressure and a wooden dowel. I read that one must always replace the circlip with a new one, so I did.