why not new rings

[Isamemon]

In the next week or two, when I have time, I have to pull the cylinders to replace the pushrod seals ( have one leaker)
I have read a lot of articles about how to do it without popping the pistons out of the cylinders
my copmpression is good and equal ( near anyway) and the bike is a 78 r80 with 49k on it
but are not the rings like about 70 bucks, so wouldnt this be a good time
of course that could open a can of worms bigger then my wallet
cause then it would be, well shcuks why not do the heads while Im at it
well why not do this and that............ :doh

[jdmetzger]

In the next week or two, when I have time, I have to pull the cylinders to replace the pushrod seals ( have one leaker)
I have read a lot of articles about how to do it without popping the pistons out of the cylinders
my copmpression is good and equal ( near anyway) and the bike is a 78 r80 with 49k on it
but are not the rings like about 70 bucks, so wouldnt this be a good time
of course that could open a can of worms bigger then my wallet
cause then it would be, well shcuks why not do the heads while Im at it
well why not do this and that............ :doh

If your compression is good, I'd leave it. Then, when you decide to get the heads done, you can go all out and replace the rings. By that time, you might need to bore the cylinder anyhow (meaning new pistons), and then you're not wasting money on a set of rings.

[kbasa]

I'd leave them too. Nikasil seems to wear forever.

[20774]

The '78 model probably still has the cast iron liners. But 49K seems a little early to have to worry about rings, since the compression seems good.

I've heard people talk about removing the clip so that piston can remain in the cylinder. I haven't done this on this era bike, but I finished up a top end on my R69S. Based upon how difficult it was to get the clip out and then get the wrist pin out of the rod end and the piston, there was no way I could have done it without completely removing the cylinder. Not that I wanted to since I was completely overhauling the engine. On the /2, you don't have the "help" of the rods to hold everything in mid air. On the /2, the cylinders bolt to the engine housing using about 25mm long studs that come through the housing. With such short bolts, you have to have 3 arms to get it done. I realize on the /7 that the clip is probably an internal circlip with is somewhat easy to remove, but the wrist pin has some interference fit which will require heating of the sides of the pistons so the wrist pin will clear. That's a lot going on...it might be easier to just remove everything and rehone the cylinder when going back together...maybe even new rings just because.

Kurt in S.A.

[DARRYL CAINEY]

The '78 model probably still has the cast iron liners. But 49K seems a little early to have to worry about rings, since the compression seems good.

I've heard people talk about removing the clip so that piston can remain in the cylinder. I haven't done this on this era bike, but I finished up a top end on my R69S. Based upon how difficult it was to get the clip out and then get the wrist pin out of the rod end and the piston, there was no way I could have done it without completely removing the cylinder. Not that I wanted to since I was completely overhauling the engine. On the /2, you don't have the "help" of the rods to hold everything in mid air. On the /2, the cylinders bolt to the engine housing using about 25mm long studs that come through the housing. With such short bolts, you have to have 3 arms to get it done. I realize on the /7 that the clip is probably an internal circlip with is somewhat easy to remove, but the wrist pin has some interference fit which will require heating of the sides of the pistons so the wrist pin will clear. That's a lot going on...it might be easier to just remove everything and rehone the cylinder when going back together...maybe even new rings just because.

Kurt in S.A.


I have done my pushrod tube seals several times this way on my 1977 R100RS.
You do not need to heat anything, just undo the snap, ring push out the piston pin with a drift the right size. Watch you don't let the rod fall hitting the crankcase.
Replace the seals the right way, reinstall the piston pin. Make sure the snap ring is facing the right way for the load!

Good Luck!

Darryl 425,000 mile RS

[20774]

I have done my pushrod tube seals several times this way on my 1977 R100RS.
You do not need to heat anything, just undo the snap, ring push out the piston pin with a drift the right size. Watch you don't let the rod fall hitting the crankcase.
Replace the seals the right way, reinstall the piston pin. Make sure the snap ring is facing the right way for the load!

Good Luck!

Darryl 425,000 mile RS

Darryl -

Those snap rings on the R69S were really a bear for me...maybe I just didn't know the "trick". I had to find something to hook the ring through the small slot and then pull it up out of the groove so I could get them out. Once out, I didn't like the idea of drifting the wrist pin out by hitting sideways on the rod...just didn't seem like a good idea. So, I used a heat gun to expand the hole in the side of the piston somewhat. Then I used a wooden dowel to drive the pin out. Worked OK, but it still was a lot of fiddling that I could not have done while trying to hold the cylinder in mid air. Just not enough hands!

Kurt in S.A.

[Isamemon]

sounds good and reasonable
Ill leave the rings for now
I dont want to "worry " about rings , just seems I am so close
but alll I really need is pushrod seals, well one this week anyway
who knows a thousand miles from now, so, :dunno
they are all gonna be done
............................
kbasa makes reference to nikasil, but I thoutht that was later in evolution of BMW.
but if this ol girl has nikasil, then I must be "lookin good"
well not me, Im ugly, im talkin about me girl
love me scooter, not tryin to take the easy way out, thats why I asked

[jdmetzger]

I have done my pushrod tube seals several times this way on my 1977 R100RS.
You do not need to heat anything, just undo the snap, ring push out the piston pin with a drift the right size. Watch you don't let the rod fall hitting the crankcase.
Replace the seals the right way, reinstall the piston pin. Make sure the snap ring is facing the right way for the load!

Good Luck!

Darryl 425,000 mile RS

I've removed cylinders more than once; including removing the wrist pin. On the 78, they have an internal snap ring, which is easy to remove as long as you have snap ring pliers. After removing the snap rings, I heat the wrist pin/piston with a hair dryer for a minute or two. Generally thats all it takes, and I can push the wrist pin out with my thumb, with a minimal amount of force.

[RandyB]

If you end up pulling the pistons out, you can always remove the rings and check the end gaps by putting them back in the cylinder. That'll get you the best answer. Careful though: Rings are brittle and sharp. While you're in there....

[kbasa]

kbasa makes reference to nikasil, but I thoutht that was later in evolution of BMW.
but if this ol girl has nikasil, then I must be "lookin good"
well not me, Im ugly, im talkin about me girl
love me scooter, not tryin to take the easy way out, thats why I asked

I was wrong on the Nikasil thang. Thanks for correcting me, guys. :buds

[jbcollier]

Randy is right. Pull the pistons and check the rings (end gap and fit in ring groove). If they are within tolerances, then don't change 'em.

[6659]

I have replaced my pushrod seals but did not take the heads off. I just rotated the pistons to TDC and moved the heads out just enough to keep them in the cylinders.

[Isamemon]

but wont the cylinders start leaking where they go to the block. when you move the cylinders out enough, isnt there a gasket there and wont that leak
I just assumed that I would have to replace whatever gasket is at the bottom of the cylinder as well as the head gasket

thanks

[flash412]

1981 was the first BMW model year for Nikasil in the USA.

[paulfinney2]

Was Nikasil in all models of 81 BMWs? and used universally since then?

[Bill Burke]

but wont the cylinders start leaking where they go to the block. when you move the cylinders out enough, isnt there a gasket there and wont that leak
I just assumed that I would have to replace whatever gasket is at the bottom of the cylinder as well as the head gasket

thanks
Three points:
1. I think your model has small o'rings at the top two cylinder studs. These o rings provide a seal for the oil flows through those top two studs for rocker lubrication. It is recommended to replace those two o rings on each side. My model (1975 /6) didn't have these, but I think yours does.
2. Yamabond 4 (available at Yamaha dealers for about $8) worked well for me as a sealant (jugs to block). I used acetone to clean everything up prior to the application of a THIN coat of the Yamabond.
3. Oak Okleshen's Top End Manual is invaluable when doing this work. A classic.

[169347]

Be very careful when using any sealants on the base area of the cylinders. Less is more . It's possible to block oil flow to the rockers when sealant blocks the path of said lubricant. Don't ask me how I know.

Woodgrain:doh