11 BMW 1977 R100RS Replace Timing Chain, Crankshaft Timing Gear & Nose Bearing

I am replacing all the engine electrical components (Dyna III ignition, alternator, diode board and wiring) as well as replacing the timing chain, crankshaft timing gear and the crankshaft nose bearing and all the seals in the timing chest cover. You can read about how I removed the engine electrical components here:

You will need to remove these components to get access to the inner timing chest cover, so this procedure starts after the engine electrical components have been removed and the timing chest is accessible.

Timing Chest Cover Exposed with Cover Puller on Crankshaft Nose

Timing Chest Cover Exposed with Cover Puller on Crankshaft Nose

Parts List

Here are the parts I used for this work.

Part # Description Qty
11 21 1 250 198 SPROCKET (to 09/78) 1
11 31 1 250 258B MASTERLINK CHAIN 1970-78
 MAX BMW Part #
1
11 31 1 250 258 7 MASTERLINK FOR DUPLEX CHAIN
 MAX BMW Part #
1
07 11 9 981 722 GROOVED BALL BEARING – 160 07 1
11 14 1 338 428 GASKET 1
11 14 1 338 429 WASHER-GASKET 2
11 14 1 262 282 CAMSHAFT SEAL – 20X32X7
(superceed by 11 14 7 705 086)
1
11 14 1 337 654 CRANKSHAFT SEAL – 28X47X7 1
11 31 1 256 861 TACHOMETER SHAFT SEAL – 7X16X7 1
11 14 1 262 644 POINTS SEAL STRIP 1976-1978 MODELS 1

Their are three oil seals in the timing chest cover, the crankshaft, camshaft and tachometer shaft seals. I replace all three of these. I replace the seal strip that  fits in the groove of the housing that contains the points and ATU.

Tools

I use the same Cycle Works tools I used for the 1975 R75/6 work.

Disassembly Procedure

I previously did this much of this work on my 1975 R75/6 and where the procedure is the same for this 1977 R100RS, I provide links to the R75/6 procedure.

New work I did on the R100RS project includes replacing the tachometer drive cable and measuring the run out of the camshaft to see if it’s straight.

Remove Timing Chest Cover

Here is the front of the engine with the engine electric components removed from the timing chest cover. The crankshaft nose is covered by the Cycle Works puller nose.

Timing Chest Cover Exposed

Timing Chest Cover Exposed

I did this work previously on my 1975 R75/6 and the procedure is the same as required for the 1977 R100RS.  I use the Cycle Works tools to remove the timing chest cover. You can read about how I did this here.

Note that the 1977 R100RS has (3) Allen head nuts and (9) Allen head bolts securing the cover.

Allan Head Nut

Allen Head Nut

I decided to use wheel bearing grease to lubricate the threads of the puller bolt this time.

Remove Oil Seals

I remove the three oil seals from the timing chest cover; the crankshaft, camshaft and tachometer drive.

Inside of Timing Chest Cover: Top-Crank Seal, Bottom-Cam Seal, Left Angle-Tachometer Drive

Inside of Timing Chest Cover: Top-Large Crank Seal, Bottom-Small Cam Seal, Left at Angle-Tachometer Drive

Front Side of Cam Shaft Seal

Front Side of Cam Shaft Seal-Inset on Front, Flush on Rear

Back Side of Crankshaft Seal

Back Side of Crankshaft Seal-Recessed, Flush on Front Side

I heat around the crankshaft and camshaft bores and remove the seals with a seal puller.

Removing Crankshaft Seal

Heating Case Around Crankshaft Seal To Ease Removal

Seals Removed: Crankshaft-Left, Camshaft-Right

Seals Removed: Crankshaft-Left, Camshaft-Right

The tachometer drive has a helical gear that can be seen from the inside of the cover. The gear turns on a shaft in the bottom of the gear.

Pulling Tachometer Drive Gear-Pivot Gear Hidden

Tachometer Drive Gear Shaft is Hidden

On the outside of the cover I can see the seal as the bushing the tachometer cable mounts in came out when I removed the cable.

Tach Drive Seal-Bushing Already Removed

Tachometer Drive Seal Visible From Front Side-Bushing Already Removed

I heat the case around the tachometer seal. I pull the gear to expose the shaft in the base of the gear. I use a screw driver and plastic mallet to gently tap the base of the helical gear to push it out. I don’t want to chip a gear tooth.

Heating Around Seal To Remove Tachometer Drive

Heating Around Seal To Remove Tachometer Drive

Pulling Tachometer Drive Gear Away from Pivot Pin

Pulling Tachometer Drive Gear Away from Pivot Pin

Using Screw Driver to Carefully Remove Tachometer Drive

Using Screw Driver to Carefully Remove Tachometer Drive

Tachometer Drive Shaft Coming Loose

Tachometer Drive Shaft Coming Loose

Tachometer Drive Coming Loose

Tachometer Drive Coming Loose

Here is the tachometer drive removed and it’s parts: the seal, a washer and the helical drive with shaft.

Tachometer Drive

Tachometer Drive

Tachometer Drive Parts

Tachometer Drive Parts

Add Timing Mark to Camshaft Sprocket

I position the crankshaft so the engine is at top dead center.

Setting Engine to TDC (OT)

Setting Engine to TDC (OT)

Since the camshaft turns at 1/2 the rate of the crankshaft, I carefully set the engine at TDC so what I think is the timing mark on the camshaft is at the 12:00 position. The timing mark is faint and I put some white paint on it. Note that it is not necessary to get this mark to the 12:00 position and you may not even see a mark on the camshaft sprocket. But it is very important to mark the valley of the camshaft sprocket that is straight up at the 12:00 position when the engine is at TDC so the relation between the crankshaft and camshaft timing is correct when installing the new timing chain and crankshaft gear.

Vertical Scratch in Cam Sprocket MAY Be the Index Mark

Vertical Scratch in Cam Sprocket MAY Be the Index Mark

Camshaft Sprocket Painted Timing Mark at 12:00

Camshaft Sprocket Painted Timing Mark at 12:00

NOTE:
The crankshaft sprocket has 19 teeth. Therefore the camshaft sprocket must have 38 teeth so it turns 1/2 as fast. This means the timing mark on the camshaft sprocket is in a valley while the mark on the crankshaft sprocket is on a tooth. But with the timing chain installed, you can’t see the mark on the crankshaft sprocket tooth. I show it later when I install the new crankshaft sprocket.

Remove Timing Chain Tensioner

The timing chain tensioner on the 1977 R100RS is the same design as the one used on my 1975 R75/6 and comes off the same way.

Timing Chain Tensioner Assembly

Timing Chain Tensioner Assembly

Before I start, I use a shop towel as a napkin to prevent the C-clip for potentially falling inside the engine through one of the holes on the front of the block.

Shop Towel "Napkin" to Keep Small Parts Out of Engine

Shop Towel “Napkin” to Keep Small Parts Out of Engine

Here is how I removed it on the R75/6.

The rubber rubbing block is in good condition so I don’t replace the tensioner arm nor the spring as I did on the R75/6.

Timing Chain Tensioner Rubber Shoe-Minimal Wear

Timing Chain Tensioner Rubber Shoe-Minimal Wear

Remove Timing Chain

The original timing chain is continuous loop without a master link. I cut the chain using a bolt cutter. The new chain uses a master link.

On the 1975 R75/6, I used a cutoff wheel to cut through the plates of the timing chain. But that created a lot of shrapnel and debris as shown here:

I rented the bolt cutter at my local rent-all place. I got a very big one with 41″ handles. I almost couldn’t fit the jaws into the available space. I suggest getting one with 24″ handles. I took me two minutes to cut the plates on the double row chain and fracture the pins on one of the links so I could remove the chain.

Timing Chain After Using Bolt Cutter

Timing Chain After Using Bolt Cutter

Remove Crankshaft Sprocket & Nose Bearing

I use the Cycle Works tools to remove the crankshaft sprocket and nose bearing at the same time. Here is how I did this on the R75/6 and the procedure is the same for the R100RS.

Note that the two aluminum puller halves have a wide and a narrow shoulder inside. The narrow shoulder goes behind the crankshaft sprocket.

Puller Part Orientation-Thicker Lip To Outside

Puller Part Orientation-Thicker Lip To Outside

Puller Parts Assembly-Thinner Lip Behind Crankshaft Gear

Puller Parts Assembly-Thinner Lip Behind Crankshaft Gear

My son bought me some 1-3/8″ box end wrenches for this puller so this is their inaugural use.

Pulling Nose Bearing & Crankshaft Sprocket with My New 1-3/8" Wrenches

Pulling Nose Bearing & Crankshaft Sprocket with My New 1-3/8″ Box End Wrenches

The sprocket teeth are not badly worn, so the mileage on the odometer is likely accurate at 37,000 miles instead of 137,000 miles. Nonetheless, I’m replacing the sprocket and nose bearing while I’m in here. And, no signs of rust on these parts unlike on the other side of the timing chest cover, so that’s good.

Crankshaft Sprocket Teeth Are Still Serviceable

Crankshaft Sprocket Teeth Are Still Serviceable

Check If Camshaft Nose Is Straight

Since the Dyna III magnet on the ATU showed it had been rubbing on the left pickup, it’s possible the camshaft nose is bent. With the timing chain removed, it’s time to check and see how straight it is. I use a dial indicator with a goose neck that attaches to a pair of vice grips. I got this set at Harbor Freight.

Dial Indicator Kit From Harbor Freight

Dial Indicator Kit From Harbor Freight

I attach the vice grips to the left side timing chest cover stud and adjust the goose neck to the probe of the dial indicator rests on the tip of the camshaft.

Dial Indicator Mounted To Check Cam Nose Runout

Dial Indicator Mounted To Check Cam Nose Run Out

Here is a short video of the measurement.

CLICK VIDEO TO RUN: Checking Camshaft Nose Run Out

The camshaft is not bent, so the rubbing must be due to misalignment of the pickup plate itself. I’ve ordered a new Dyna III ignition.

Installation Procedure

I refinished the timing chest cover to remove the corrosion and bring the finish back to as close to original condition as I can. I install new metal diode board mounts to replace the original rubber mounts.

I install a new timing chain, crankshaft sprocket and nose bearing and timing chest cover gaskets. The procedures are the same as what I documented for the R75/6.

Install New Crankshaft Sprocket

Install New Crankshaft Nose Bearing

I marked the crankshaft sprocket teeth behind the timing mark so I can see the mark when the timing chain is installed.

Crankshaft Teeth With White Paint Aligned with Camshaft Gear

Crankshaft Teeth With White Paint Aligned with Camshaft Gear

I moved the timing chain one tooth off to show how much misalignment occurs between the timing mark on the crankshaft and camshaft sprockets.

Timing Marks When Sprockets Are One Tooth Out of Alignment

Timing Marks When Sprockets Are One Tooth Out of Alignment

And here’s how the timing marks look when they are correctly aligned.

Correct Gear Alignment

Correct Gear Alignment

Install New Timing Chain with Master Link

The procedure is the same as I followed for the R75/6. This time I used masking tape to cover the holes in the engine case. I want it a bit sticky, but not too sticky so I can remove it easily. The trick is to rub the sticky side across my pants leg a couple times before sticking it on the engine case.

Covering Engine Holes with Masking Tape

Covering Engine Holes with Masking Tape

Note that the master link chain comes with two C-clips to secure the plate on the master link. These are very small and harder to install than a fish clip. I purchased a second master link with a fish clip. The link looks like the one that comes with the C-clips, but it is different. The grooves in the ends of the pins are wider. I got them mixed up and couldn’t get the fish clip to go on. I removed the link and found this difference in how they are made.

Install Timing Chain Tensioner and Spring

Although the following procedure shows installation of a new timing chain tensioner and spring, it’s the same procedure for installing the original parts on the R100RS.

Clean Timing Chest Cover & Engine Block

The timing chest cover has corrosion around the top, sides and on the outside.

Front Engine Cover and Timing Chest Cover Corrosion

Front Engine Cover and Timing Chest Cover Corrosion

Grunge and Corrosion On Outside of Timing Chest Cover

Grunge and Corrosion On Outside of Timing Chest Cover

I decided to clean the cover using bead blasting followed by an experimental home brew vapor blaster I have access to.  Here is the result; the corrosion is gone and it looks like new again.

Restored Finish on Timing Chest Cover

Restored Finish on Timing Chest Cover

Restored Finish on Timing Chest Cover

Restored Finish on Timing Chest Cover

Restored Finish on Timing Chest Cover

Restored Finish on Timing Chest Cover

Install Crankshaft Front Seal, Camshaft Seal and Tachometer Seal

I didn’t replace the tachometer drive seal on the R75/6. Here’s how I replaced the crankshaft and camshaft seals in the timing chest cover.

Restored Finish on Front of Timing Chest Cover

Restored Finish on Front of Timing Chest Cover

I install the tachometer drive with the parts in the following order.

Order of Parts on Tachometer Shaft

Order of Parts on Tachometer Shaft

I put a bit of engine oil on the circumference of the seal and I use a socket and extension to drive the tachometer drive and seal into the bore from the front side of the timing chest cover. I didn’t heat the seal bore and the assembly went in smoothly.

Tachometer Shaft, Seal and Driver

Tachometer Shaft, Seal and Driver

Driving Tachometer Shaft and Seal

Driving Tachometer Shaft and Seal

Here is how deep the seal goes and how it looks inside the drive housing.

Depth of Tachometer Seal

Depth of Tachometer Seal

New Tachometer Seal Installed

New Tachometer Seal Installed

Install New Metal Diode Board Mounts

I removed the original rubber diode board mounts and ground wires. I install new metal mounts from Euro MotoElectrics.

Euro MotoElectrics Solid Diode Board Mounts With Extra Nut & Washer

Euro MotoElectrics Solid Diode Board Mounts With Extra Nut & Washer

Installing Metal Diode Board Mounts

Installing Metal Diode Board Mounts

New Metal Diode Board Mounts Installed

New Metal Diode Board Mounts Installed

Install Timing Chest Cover

The procedure is the same as I followed for the R75/6.  It’s important to clean the gasket mating surface of the engine block and the rear of the timing chest cover before mounting the gaskets. Here is the procedure.

I’ve had good success by heating the cover in the oven to 275 F. The cover slides on the crankshaft nose bearing easily, so I have not needed to use the Cycle Works tools. I installed new stainless steel bolts from a bolt kit in the four bottom holes which are outside the front engine cover and used the 5 of the original Allen bolts and 3 Allen nuts and torqued them down.

NOTE:
This time the nose bearing did not seat all the way into the bore of the timing chest cover. I did not find that out until a day later when I tried to rotate the engine by turning the flywheel in preparation for removing the flywheel to replace the rear main seal. It was very hard to turn the engine. I had installed all the engine electrical components on the timing chest cover, so they had to be removed. Then I loosened the (9) Allen bolts and (3) nuts and the flywheel easily turned the engine again. I heated around the front crankshaft seal with my heat gun until it was 190 F, used a plastic mallet and a socket extension and tapped around the ridge in the timing chest cover surrounding the seal. When I torqued the bolts and nuts again, the flywheel remained easy to turn.

So, an easy test to tell if the nose bearing is seated all the way in the bore is to try turning the flywheel when you have the bolts and nuts torqued and it should be very easy to turn (assuming the spark plugs are out).

Here is engine with the new timing chain, crankshaft sprocket, nose bearing, refinished timing chest cover with new crankshaft, camshaft and tachometer drive seals. They should be good for another 40 years.

Timing Chest Cover Installed

Timing Chest Cover Installed

The next work is to install the new engine electrical components and wiring harnesses. You can read how I do that here:

4 thoughts on “11 BMW 1977 R100RS Replace Timing Chain, Crankshaft Timing Gear & Nose Bearing

  1. Hi Brook
    I’m impressed with all your articles and photos on your BMWs. I still have my 77 RS in virtually stock condition with the exception of snowflake wheels, CC ss exhaust, and different shocks. It sits quietly in my garage with some avgas in the tank and a batterytender attached. Last time I ran it it started immediately and ran smoothly.
    I like the finish you got on your timing cover. I know you bead blasted it but what’s the brew vapor method? A good friend with a complete machine shop has a oven for cleaning cranks, blocks and anything else that’s cruddy with filth and grease.
    I am currently finishing up rebuilding a 1951 Vincent Black Shadow for an old friend. Basically bolting and screwing everything back together and bolting it onto the rebuilt engine. Like the BMWs, all the rotating parts ride on tapered bearings.
    Keep up the great work,
    Regards,
    Mac Morgan

    • Hi Mac,

      Thank you for the kind words about this site. After awhile, I ended up with quite a few procedures documented. But there’s lots more to do that I haven’t gotten to do yet.

      By hand, I can get a good finish with aluminum cleaner, and steel wool (00 down to 000) followed by aluminum polish. I documented a number of products and techniques I use with the “hand method” here:

      –> http://brook.reams.me/bmw-motorcyle-rebuilds/1973-bmw-r755-rebuild-project/51-bmw-r755-refinishing-techniques/

      The vapor blaster is an “experiment” by the owner of a small vintage British bike shop I work in a couple days a week. It’s not something I’d recommend anyone try to copy as it’s a shade tree design with a number of limitations.

      Cool beans on having the opportunity to work on a Vincent BS. IMHO, it’s a bike with a beautify and distinctive visual design that compliments it’s legacy for speed.

      Best.
      Brook.

  2. Hi Brook,
    Thank you for posting your work, it has been incredibly insightful. I’m a new owner of an R75/6. Recently, I detected a leak at the tachometer drive seal. In your opinion do you think there is a way to remove and change the seal without removing the timing chain cover?

    Thank you for the time to read this and the advice!

    • Hi Keith,

      I’ve not tried to do that, so I have no experience to share. It’s a tight fit. I vaguely recall someone saying it was possible. Perhaps a “hook” that you can slip under the lip to pull up on the seal will work. I would heat the aluminum housing around the seal to get as much expansion of the hole as I can. I might also put some kroil or other “rusty nut” lubricant around the seal to help it slide. Then I would try the hook and pull on one side and then the other to wiggle the seal and get it to slide.

      Again, the above is speculation on my part as I have not replaced the seal with the cover in place on the engine.

      I hope this helps.

      Best.
      Brook.

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