Pushrod tube seals

So, one of the seals is leaking enough to leave spots on the garage floor. I am thinking of doing the job myself. I have all the tools I believe I need save for a ring compressor. I would appreciate any thoughts as to how difficult a job this is -- I take ti the R&R of the cylinder is the bis issue. I've never pulled one off a 4 stroke before. An thing else to be worried about. Mileage is 44k and it was running well when I put it away last fall.

Do you have the proper tools, such as a torque wrench, exhaust nut wrench, new gaskets etc.? Get a manual and read it is the best advice. You dont need to remove the pistons. What bike are you working on? Not a hard job but certain steps need to be followed.

This is generally not a difficult job, maybe 3 out of 5 wrenches on a scale. Often times this is done during weekend tech days...of course with lots of eyes looking on as well.

In my mind there's a couple of ways of doing this:

1) pull off the cylinder enough to slip the new pushrod tube seals in place and reinstall
2) pull off the cylinder enough to remove the circlip holding the piston the conrod, then leave the piston the cylinder and pull the whole unit off
3) pull everything off including the piston off the conrod

For 1) and 2), it's possible to leave the 6 and 12 o'clock head bolts tight, and pulling things off rather quickly and then finishing up. I would think leaving this setup with the head torqued too long (overnight?) could result in head warpage...I would not do that.

The issue with 1) is the difficulty in getting everything very clean plus the small O-rings on the top studs can't be replaced. 2) is better in this regard. 3) allows the opportunity to really look things over, make cylinder ovality measurements, decarbon the piston/combustion chamber, etc.

Oak Okleshen sells a booklet that is a valuable resource for doing all of this. Last I knew it was $25. He's not on-line but can be reached using the contact information for him found in the link in my signature line.

As 20774 said.............

I used option 1 a few times which goes fairly quick.
IIRC just standard tools and a torque wrench & exhaust wrench.

You can see the small top stud o-rings in the image.
It's not been a problem for me that these did not get replaced. YMMV
Be careful to get them in place before sliding the cylinder home.

The next time I do this I'll probably go with 3.

<a href="http://s1089.photobucket.com/user/brittrunyon/media/1992%20R%20100%20GS%20-%20ZED/P9262310.jpg.html" target="_blank"><img src="http://i1089.photobucket.com/albums/i358/brittrunyon/1992%20R%20100%20GS%20-%20ZED/P9262310.jpg" border="0" alt=" photo P9262310.jpg"/></a>

Happy Wrenching

There are always shortcuts. Sometimes they work.

I am getting ready to do the same job again myself.

I have done it several times on my old bike with mixed results.

I always pull the cylinder & piston out together just enough to get the circlip out.

The last 2 times all 4 pushrod tube rubbers cracked and started leaking again.

I am ordering all parts from Max BMW, as before they came from a different supplier.

Wish me luck!

I am not an experienced wrencher, but have successfully done three airheads, using Kurt's option #3 and Oak's manual. There are also some u-tube videos out there on the web that are helpful to give you a taste for the overall operation.

In addition to cleaning the carbon deposits off the head and piston, removing the jugs and piston make it easier to clean off all the residual base gasket material and get a clean, ultra thin bead of new gasket material when replacing the jugs (don't block the oil galleries above the cylinder studs).

Last time I accidentally slipped a piston out of the bore, but used a large hose clamp to compress the rings and it was easy to reinstall.

The hardest part for me is always the piston wrist pin circlip removal and installation (use new ones), cause I have cheap HF circlip pliers...Take Oak's advice and block off the opening to the engine case with shop towels so if the clip goes "boing" and flies away, it won't fly into the crank works....

have fun...a clean motor and garage floor are within your reach!

I get so very tired of these seals turning hard enough to start drooling as often as mine do. I wonder if you could scan a new one and then 3-D print them in high-temp silicone or some other space-age material that won't harden up so fast?

ccolwell said:

So, one of the seals is leaking enough to leave spots on the garage floor. I am thinking of doing the job myself. I have all the tools I believe I need save for a ring compressor. I would appreciate any thoughts as to how difficult a job this is -- I take ti the R&R of the cylinder is the bis issue. I've never pulled one off a 4 stroke before. An thing else to be worried about. Mileage is 44k and it was running well when I put it away last fall.

Click to expand...

You don't need a ring compressor. The old tried-and-true method works - thumb nail, and screwdriver pressure on ring, and slight pressure on cylinder to push it over the ring - one-at-a-time. You just need to be careful.

Thanks to all. Looks like Oaks book and #2 for me. It seems getting the exhaust nuts off will be the worst of it. I would not have guessed you could do it and leave the head on, but the pic above shows me wrong.

I suppose in a crazy situation, you might be able to separate the crossovers, remove the muffler clamps, and slide the head and header/muffler with it. However, those crossovers tend to be nasty and nearly glued together. Plus you'd be putting quite a bit of stress on the header/flange connection.

I'm sure you've read all about removing the exhaust nut to be watchful for that seizing/galling when you try and remove it. Be careful.

ccolwell said:

So, one of the seals is leaking enough to leave spots on the garage floor. I am thinking of doing the job myself. I have all the tools I believe I need save for a ring compressor. I would appreciate any thoughts as to how difficult a job this is -- I take ti the R&R of the cylinder is the bis issue. I've never pulled one off a 4 stroke before. An thing else to be worried about. Mileage is 44k and it was running well when I put it away last fall.

Click to expand...

Purchase Oak's Top End Manual, it is step by step! Never having done the job it is your best bet to keep from screwing up.

Additionally search this forum and the Airheads Beemer club website airheads.org. You DO belong to the Airheads club right?? There are fellow Airheads in your area who will be glad to help.

I always pull the heads, simply because it is an excellent opportunity to remove the carbon from the heads and pistons.

Take LOTS of digital photos as you go along, you can NOT have to many photos of the process.

I have used this tool - found at a yard sale decades ago - numerous times to reseat those pesky push rod tube seals without ever picking up a wrench.

tattube -

Yes those kind of "tools" have been shown in the years past...one of the aftermarket manuals also shows them. The only issues I can think that might give one pause in using those are:

- some of the collars on the pushrod tubes are brazed onto the tube...hitting the collar with this tool serves to pull the tube out of the head, or breaking the brazing and now the collar can't hold enough pressure on the seal. Now you have two problems.

- putting additional pressure on the seal can cause them to split, resulting in a higher rate of loss of oil when before it was just a minor annoyance or trickle

On a scale of 1-10 for mechanical ability/experience, I'm about a 6. Did mine 2 years ago and all's well. Left the piston in the jug. The only advice I would give is if you have the old style circlip buy a couple extra. They are fairly easy to get off but can be a PITA to get on! They will deform with too much force and can become a dangerous projectile so wear safety glasses.

Picture of old style: https://encrypted-tbn0.gstatic.com/...LhML83AdzaS1FjJFuMjKXzrT7qtTuNbHDSTOcmi9xCE8Q

For a great tutorial: http://www.pbase.com/dqmohan/prtseals

Chris Harris also has three separate youtube videos on pushrod tube seals...they're listed in the link in my signature line.

A week of penetrating oil, a little heat and the exhaust nuts came off without any hint of sticking. Picked up parts and valuable advice from Tom Cutter the other day. Next week I'll have at it. Any suggestions as to what to use to decarbon the heads and pistons?

ccolwell said:

Any suggestions as to what to use to decarbon the heads and pistons?

Click to expand...

Oak had suggested using Hyrdoseal. I bought a jug of the stuff through a local hardware store and soaked them in it for a week or so. Worked well enough that I could use a piece of wood to scrape away just about all of the carbon. My goal was not make them mirrored surfaces!! I suspect that people will suggest Simple Green. Be aware that it can be harmful to aluminum if allowed to remain in contact too long...I don't know what that is, but I would think a week is too long. Plus, Simple Green should be diluted 50-50 IIRC.

I would use the google box at the top of the screen and type in "site:bmwmoa.org simple green" and "site:bmwmoa.org hyrdoseal" and find other threads that discussed this.

ccolwell said:

....... Any suggestions as to what to use to decarbon the heads and pistons?

Click to expand...

I used carb cleaner and a couple different plastic scrapers. Both heads and pistons less than an hour.

I watched the 3 Chris Harris videos on how he does the Push Rod Tube Rubbers and was very
surprised that he uses no gasket sealer of any kind!

When I ordered my parts from Max BMW the parts guy recommended Hylomar.

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