Head/barrel install - Advice needed

[r65lsk75c]

I managed to get both barrels over the pistons on my '82 R65LS. Now it appears that the new pushrod tube seals do not go far enough into the block to allow to cylinder to seat on the engine block. There is probably a 2-3 mm gap on both sides and the large o-ring is still visible. Is there a good method for moving the cylinder the last few mm? Will it pull down when I tighten the head bolts? Should I try a bit of brute force (maybe fabricate a tool to drive the pushrod tubes) to get the seals seated in the block?

Advice is welcome!

Rick Tyson
'82 R65LS
'87 K75C
'74 Triumph Trident
'75 Norton Commando

[88bmwJeff]

I just replaced R&R the left jug on my 88 R100 RT, and I had the same issue. I slowly tightened the head bolts and everything tightened up just fine. The pushrod seals seated properly. I don't know if its recommended or not. No leaks to date though.

[pmdave]

It's the pressure that squeezes the pushrod seals into place. DO lubricate the rubber seals with engine oil. DO NOT get any base sealer on the rubber.

I've had good success with that gray silicone based "foreign" goo from the auto parts stores for sealing cylinder bases. Be careful around the base of the studs where the O rings are. That's where oil squirts up the stud holes to lubricate the rocker bearings.

pmdave :brow

[pmdave]

BTW, you can use a large hose clamp to compress the rings for insertion into the jugs. Lubricate, of course. And, to back up a step, before pushing those pistons in the holes, remove the rings, insert in the bores, and check end gap is within spec at both top and bottom of bore. It's easier before the piston is installed on the rod, since the piston can be pushed down (upside down) to get the ring square in the bore.

Reinstall the rings (noting correct side up) on the piston, and rotate the rings so the gaps don't match. I normally position the oil ring gap up, and the other two rings at 4 and 7 o'clock.

pmdave

[r65lsk75c]

I assume from the recommendation for using a sealant at the bottom of the cylinder that there is not a gasket used here. I posted the gasket question a short time ago but did not get a response. No gasket is shown in the factory manual or on several online parts fische. Do you just smear a thin layer of sealant around the entire barrel/block mating surface trying to avoid the area close to the two stud o-rings?

By the way, I did use the two hose clamp approach for ring compression. After a bit of practice, it worked pretty well. Now I simply have to get the barrels snug against the engine block and I can get on with putting the rest of the engine together.

Thanks again for the advice.

Rick T

[pmdave]

There have been a number of different methods for sealing the cylinder to the block. Some use a large O ring in a groove cut in the outside of the cylinder "spigot". Some use a small dia. big O ring that goes around the base of the spigot. And some older machines had an aluminum spacer that also served as a "gasket".

The studs also serve as the oiling source for the rocker arms. Pressure actually squirts past the threads in the block and works up the stud hole in the cylinder. I'm thinking it's the upper studs on each side, but follow the book, not my antique memory. And what follows isn't BMW gospel.

BMW suggested a special sealer, but frankly it wasn't great. What I do is coat the block and jug contact surfaces with RTV silicone gasket goo, and assemble. I'm careful to not get any goo on the crank end of the spigot, where it could get into the oil. I avoid any goo in the valve lifter area or on the rubber pushrod seals. And I keep the goo outside of the O rings sealing the stud holes. The "goo" I prefer is Permatex Ultra Grey RTV silicone gasket maker 599BR

I clean the aluminum carefully with clutch/brake cleaner to remove any traces of oil or debris. Then the pushrod seals are positioned and lubricated with motor oil, the piston is inserted and the spigot partially inserted in the block. I smear the goo around (my finger seems to be a good tool, plus a small screwdriver for the hidden areas) push the jug in, pop on the head gasket (be sure it's correct side up so the holes line up with the pushrod holes) add the head, pushrod, rocker and blocks and start snugging down the nuts in a cross pattern. Watch that the pushrod seals are sliding into position and not getting pinched. Tighten in stages, around the pattern until the cylinder is seated. I usually wait a half your or so to allow the gasket goo to set up, then come back and torque the nuts.

Check the end play of the rockers. They should be free to rotate, but not have any end clearance. If they click up and down, ease off both nuts on the rocker blocks, and squeeze the blocks snug against the rocker with a large C clamp and a couple of appropriate short sockets. Torque the nuts, then release the C clamp.

If you can't remove the exessive rocker end clearance, it's time for some late model BMW rocker shims. It would be good to know this before you assemble, since you have to unbolt the rocker blocks to insert the shim.

My experience has been that once the gray gasket goo has set up (say 24 hrs) you can remove one rocker assembly at a time without disturbing the seal.

One additional caution: if you have used rubber bands to hold the con rod from banging down on the edge of the hole, be absolutely certain you remove them before attempting to install the jug. A rubber band caught between the crankcase and the cylinder spigot can crack the spigot. You don't want to know how I know this.

pmdave

[AntonLargiader]

Make sure you have the correct pushrod tube seals. There is one for just the R65 (ends in 090) and another for nearly everything else (ends in 995).