Replacing a Timing Chain on BMW airhead motorcycles

Replacing a Timing Chain
on your BMW airhead motorcycle

Understanding your motorcycle's chain operation; advice and hints on replacing it and necessary associated parts.

Preface:

Replacing a chain is not overly difficult, but for the vast majority of airhead owners, it is one of THE complex jobs that might be tackled. 'Complex job' herein means such as a transmission overhaul, rear drive overhaul, and engine crankshaft removal, camshaft removal, etc. The timing chain job is probably the simpler of these. Most folks will find that a timing chain job is MUCH easier to do than a transmission overhaul...as you do not need some very specialized tools, and do not need to know too many 'tricks'; nor, deal with all the variations, in a transmission job. No precision tools are needed for a timing chain job.

A proper chain replacement job will always involve a new bearing, new guide/follower shoe and new tensioner, and usually a tensioner piston spring...and usually a new crankshaft sprocket. It might include a new camshaft sprocket (they wear more slowly than a crankshaft sprocket).

What is it? Where is it? What does it do? What happens when it wears out?

Your BMW airhead motorcycle's engine has a crankshaft located in the middle of the engine, and that crankshaft drives the lower located camshaft via a chain. A chain is used rather than gears, as a method for adjusting the mesh of gears would be needed over the life of the gears and associated bearings. Gears can also be very noisy, especially if not totally immersed in an oil bath, so are rather difficult to quiet down, especially considering the expansion rate of the aluminum case...and using gears would reverse the direction of rotation of the camshaft unless an extra gear was used as an intermediate idler. That adds a LOT of complexity. BMW could have designed the camshaft to rotate in the opposite direction, compared to the crankshaft, but for several reasons, did not.

The chain is located between the engine casting and the timing chest middle casting, and is hidden from view even if you remove the timing chest outer cover. The crankshaft nose area has a sprocket and a bearing pressed onto it. A sprocket is a type of gear that meshes with chain rollers.

The chain travels from the crankshaft sprocket to a larger one, located below, on the camshaft, and then back to the crankshaft sprocket;... The ratio of the sprocket sizes is such that the camshaft rotation is exactly half that of the crankshaft. The chain travel, as you face from the front, is clockwise. Another way of saying that, is that the engine rotates clockwise, faced from the front. Since the camshaft is a load on the crankshaft, that is, the crankshaft is the driving force via the chain for the camshaft, then ONE side of the pockets of the crankshaft sprocket have the most pressure on them when the throttle has the engine applying power, and the other side of the chain roller sprocket pockets have some force, when the throttle is backed off. The result of this is that you can SEE if the sprocket is excessively worn, by a simple visual inspection. Viewing sprocket roller pockets towards the top of the crankshaft sprocket, if the left sides are quite worn, then the crankshaft sprocket needs replacement....almost always this is true. For the camshaft sprocket, the force is similar, but the sprocket size distributes the forces over a wider area, and it is probable that the sprocket is somewhat harder...so the camshaft sprocket is not replaced as often.

The camshaft operates the cylinder head valves, the oil pump, and the ignition triggering points or electronics. The forward end of the crankshaft has not only that sprocket and bearing, but also the alternator rotor. The engine rotates in only one direction during operation, clockwise as facing from the front, and as the engine rotates, the chain on the pulling side of the sprockets, the left side, will be taut, and the other side looser. There are one or two 'shoes' that the chain rides against, that are spring or hydraulically loaded, so to maintain some sort of chain tightness. Otherwise the chain would whip around, especially from throttle on-off and/or shifting gears if not perfectly synchronized, and the chain would be rather soon stretched and the sprockets well worn.

From the beginning of the /5 series, through 1978, the chain was DUPLEX (two sets of rollers in width). That chain was at that time an ENDLESS type, that is, no clip and master link was used, the chain was installed together with the sprockets, all as an assembly. For the average person, as well as the shop pro, this was NOT an overly pleasant situation. Today, master-linked chains are used for both Duplex and Simplex chains.

In 1979 BMW made a considerable number of changes, one of which was to use a SIMPLEX chain (one set of rollers in width), and they also changed the method of tensioning the slack in the chain, a new hydraulic method was incorporated. At that same time a master-link system was incorporated. The master-link makes the chain easier to replace, both sprockets not necessarily needing removal...or replacing. Many will cuss at replacing the master link, 'easier' is not 'easy'. Note, however, that the chains don't wear much, but the crankshaft sprocket DOES. Note also, that if you follow the hints and advice in this article, you will find that installing the master link is not as difficult as you might be trying to make it appear!

The chain stretches, some anyway, from normal use. The amount of stretch is actually very small, is almost entirely in the chain rollers area and not the side plates, and what is typically called a sloppy or worn chain is really the much higher amount of wear on the crankshaft sprocket. A removed chain from an engine with fairly high mileage, compared to a brand-new chain, may well look nearly identical in length. There will be some differences, especially if twisting the chains. BMW seems to have made the crankshaft sprocket of a slightly softer material than the camshaft sprocket.

As wear proceeds, which it does from day-1 of new parts, the camshaft will begin to lag the designed timing relationship to the crankshaft,; and, thus, the timing of the camshaft itself will retard in relation to piston movement, and the ignition also is retarded. The wear occurs rather slowly, and it is usually not noticed by the rider that the power has been slowly reducing. The ignition is usually checked every 5000 or 10,000 miles, and its timing setting is adjustable, and one will probably not notice the very tiny compensating changes one makes in ignition timing, made over many many miles. This is very especially so with points ignition. Thus, the ignition point will remain more or less correct in relationship to the pistons and crankshaft markings for ignition purposes, but the valve openings and closings will lag, versus the pistons.

It is hard to give any type of firm mileage at which a chain should be replaced. It is also hard to give more than a few 'rules' to help reduce chain wear.  The chain itself does not wear all that much...but....for both chain and OTHER components.... certainly lengthy low rpm idling is not good.... as the oil supply is reduced...as the oil for the chain comes from the pressure release valve area above the chain. See item #8, well below.   This means that trying to get the lowest possible rpm for idle is a BAD idea.      Rapid on-off throttle movement probably accelerates wear, as does excessive use of the very highest rpm area.  As a very general rule, for most things mechanical, wear tends to increase more exponentially than directly, from incremental increases in rpm, this is especially so at the higher rpm levels.    If shifting, especially downward, is done jerkily, with large excursions of rpm, that may also accelerate wear.   Chains/sprockets/etc., can be worn excessively in 30,000 miles....or 150,000 miles.   Perhaps most bikes will signal a need, from unstable ignition marks as seen with a strobe lamp, or, from power reductions, but especially from noisy chains (Duplex, especially) at idle rpm.... for replacement around 85,000 miles.

If the chain and sprockets wear enough, the tensioner's will not do a very good job and the chain will slop around, and may well start rubbing against the bearing carrier, and one may find some metal particles in an unrolled engine oil filter. Chain slop causes the ignition to jump around due to the irregular loading of the chain by the camshaft, and the timing will likely start having a difference BETWEEN the two cylinders, and this can cause vibration.   It is entirely possible to find some plastic/hard rubber guide parts in the folds of the oil filter element (one should disassemble filters at every filter change, and inspect all folds, inside, outside).....these may be tiny globules of melted plastic-like substance.

The simplex and the duplex chains models do not sound the same when they wear considerably, and only with considerable experience will someone know what the difference sounds like.

There is no really good method of positively determining a chain and sprockets and tensioner/guide condition without considerable labor in removing the front of the engine.

HOWEVER:
For the canister ignition models (1979 and later), the split image tends to be a good clue as to worn chain and sprockets, as these models have a more precise method of operation. That is, the triggering of the ignition is more precise between left and right cylinders as the cam jerks about a bit. This is particularly so for the electronic canister trigger models (1981+) where one can be relatively certain that a split image (perhaps over 1/16" or certainly over 1/8") is due to chain and sprockets, as opposed to the 1979-1980 POINTS canister models where some irregularities in the points area can possibly cause a slightly bigger split image. Anything over 1/8" is ONE clue that a chain job MAY be necessary. SOUND at idle, hot engine and hot oil, is another clue....there may be a very distinct chain rattle noise. That noise might be quite noticeable to the average owner, at 900-1000 rpm, and less so at 1200 rpm.

NOTE, that in the models PRIOR to 1979, a bent camshaft tip can cause a larger split in the timing image. In fact only .001" of runout on the cam tip will cause a very noticeable split image. That is usually fixable, the fix is not part of this article, and it involves making sure the bearing is not overly worn, and using a dial gauge on the camshaft tip and hitting the tip with a small brass hammer in a very careful manner. In some instances, the two lobed cam that is part of the automatic mechanical timing advance mechanism on the PRE 1979 models might need slight attention. That is not commonly done anymore.

NOTE: timing chains for all models are available with master links; not necessarily from BMW. Removing an old non-master linked chain is best done by cutting.

The Details:

It is NOT overly difficult to do a timing chain job, even for the average owner, but there are MANY special 'hints and tricks of the trade'. I will attempt to lay out all of these, that I know of. If you feel REASONABLY competent to remove a cylinder to replace the pushrod tube rubbers, you probably are going to have little trouble with a chain job, if you follow instructions here.

You are probably familiar with the alternator and ignition triggering parts, as those are very easily at hand after removing the front outer cover. The bearings, sprocket gears, tensioner and chain, ETC., are located REARward of these parts, behind that timing chest area. You have to remove the outer parts and then the timing chest casting for access to the timing chain. If your motorcycle has rubber diode board mounts, NOW is the time to order the solid metal mounts....It is VASTLY easier to install these VERY worthwhile metal mounts (Thunderchild or Motorrad Elektrik's are both good) during a chain job.

In 1979, coincident with the change to the canister ignition and the change from the duplex chain to a simplex chain, there was an incorporation of a spring loaded hydraulic damper for the chain. That spring is 68 mm long. See item #8, well below.

Purchase chains with a master link/clip so that both sprockets and chain do not have to be removed and replaced as an assembly, which is the method seen in much of the literature. BMW sells ENDLESS chains for DUPLEX. Old NON-masterlinked chains were usually removed by high speed cutting tool or very strong chain link cutter. Master link type of simplex chains may already be installed. Use of cutting is completely acceptable...keep bits out of the engine lower end though.

There are some other chain bits and pieces available from such as for Mercedes cars, frankly it is not of much importance at this point....and I don't do this Mercedes stuff myself. I only mention it because some have done a chain job with these parts; where BMW only offered an endless (SIMPLEX) chain;.....again, I WILL NOT, AND DO NOT.

If the chain drive system becomes too loose it might flop around and eat away at the front main bearing housing, depositing metal flakes into your oil filter, not a good thing (you DO use large side-cutters, remove the filter end caps, and unroll the filter paper at each filter change, and fully inspect?). This happens more on the Pre-1979 bikes with the duplex chain. A modest amount of chain slop is not really damaging much, and you will hear the chain flopping around at idle rpm on a hot thoroughly warm-up engine. Besides the chain needing replacement, you will also have to replace the gaskets, seals, tensioner shoe(s), guide, the spring inside the damper piston, and almost for sure the crankshaft sprocket and the bearing. It is probably penny-wise, pound-foolish, to not replace parts as reuse, such as of an old rather worn crankshaft sprocket, will not only accelerate wear on your new chain, but the engine performance will REALLY suffer, as a worn crank sprocket gives poor ignition stability and lousy engine idling....and using an old relaxed pressure spring is also not a good idea. Whilst, for curiousity, most folks will check the crank nose bearing (or, for that matter, any such bearing) by 'feel' and 'rotated sound', and a crankshaft bearing may thusly check out OK; that bearing SHOULD BE REPLACED...why take the chance that its clearances are getting sloppy? I RECOMMEND....you replace ALL the parts, INCLUDING and ESPECIALLY that bearing!!!!

NOTE: The oil pressure relief plunger must operate smoothly, and the spring in it should be at least 68 mm long when relaxed...if not, install a new one.

The chain is lubricated by flow out of the oil pressure regulator located at the top area. Because of that, the chain and sprockets, etc., may well get INsufficient oiling at idle rpm, particularly with hot oil, and thus excessive low rpm idling time is always a BAD idea.

I am going to REPEAT some previous information you read well above in this article, saying things differently, and add some things.....before we get into the real meat:

***A worn chain (from this point, Worn Chain means wear of all the parts mentioned...as a system of parts) causes other problems, and not just some noise or a few teeny flakes in the oil from the front bearing housing. When the crankshaft is rotating, CW as you face from the front, the crankshaft sprocket, being the POWERED sprocket, is pulling the chain upwards, on the left side. As the chain/sprockets wear, this is only somewhat compensated for by the tensioner on the right side, and only partially compensated on the late models by the guide on the left side. Thus, the camshaft is, in effect, from the very first ever engine start, slowly lagging the crankshaft more and more as the chain wears. This changes the timing of the camshaft (and thereby the valves) relative to the pistons. The effect is very slow, cumulative, and most do not notice the lowering of the power output, in fact most do not notice the excessive chain slop noise until it is pointed out to them. Another effect is on the ignition timing. As the chain/sprockets wear, one must readjust the timing to compensate. You then have the timing set correctly for piston position, but the camshaft is lagging!

On the pre-1979 models, the points are located, unsupported by any outrigger bearing, at the nose of the camshaft, and that camshaft nose may be ever so slightly bent. In fact, only 0.0008" of runout on the tip is the specification limit. Any runout makes for different ignition timing between the two cylinders, as there are TWO lobes on the IGNITION cam, located in the camshaft tip area (part of the automatic advance unit). Even if the runout is quite small, there will be developed ignition timing discrepancies. Since the camshaft that operates the valves is an UNeven load on the chain, that makes the chain jerk about somewhat, more as the chain gets sloppier. That makes for even more spread dual image, a timing variation between cylinders, as seen on the flywheel with your ignition strobe light. Any irregularity, run-out, ETC., on a cap tip, or in some part of the ignition triggering system, will also contribute. Thus you can get ignition irregularities from more than once source, and if enough, you will not only get a wee bit extra idling roughness, but also some higher rpm vibration. This higher rpm vibration may trick you into thinking the carburetor throttle cables need synchronizing. You could get engine vibrations well away from the normal 4250 rpm (or so, depending on model)....at several rpm areas. All sorts of combinations of things are possible. A worn chain/sprocket can definitely cause poor idling.

For the 1979-1980 models, the cam tip type drive was abandoned and the canister points models use an offset keyway drive off a large flat nose of the revised camshaft. This reduces the split image problem from the points area by making the timing better controlled over the entire rpm range. On the 1981+ electronics models, the points were eliminated, and the timing is more precise than all the points models, and certainly there are no high rpm irregularities from points....and no points to wear (and be replaced regularly).

But, on any 1979 and later model, chain wear will still cause ignition irregularities. 1/8" of split image distance is usually acceptable, but at 1/4", it is really time...past time!...to replace a chain. Certainly, excessive chain noise and/or fine flakes in the oil filter pleats is a warning that it is time to think SERIOUSLY about a change of timing chain and associated parts.

The MEAT!

Firstly: Do all this work with the engine at the OT (TDC) mark! At this setting on the flywheel/clutch carrier, you have a reference. LOOSEN the valves rather completely so pressure is off the camshaft. Remove the battery negative wire(s) and start work on the front area. You will find that if the wheel and lowers are removed, this is an easier job, but that is up to you. MAKE NOTES on where the various bolts, etc., go, as you remove them; some may be of different lengths. The first thing to do is remove the front outer cover, so you can then remove all the alternator parts. Well, actually, the first thing to do is to disconnect all the battery negative post wires!

You will have to heat around the alternator seal area in order to free the bearing from the inner cover. Try reinstalling a lower inner cover allen screw, and pull...tap with a plastic or other very soft hammer onto the area near the top. The cover should free up.

To restate this differently: to allow the chain case cover to be removed and replaced easily, this is done with it HOT;....heat the cover around the crankshaft ball bearing. NOTE those words "..AND REPLACED"! That means you heat it again, when replacing it!

1. Use of a BMW puller for the crank sprocket (removed after the chain and front bearing is removed) is wonderful if you want to get one or have access to one. It is NOT a must, and has problems, as do all tools. The crank nose/taper must be protected against damage of any kind. I highly recommend that you use the BMW tool, or, a common heavy duty three jaw puller and remove the crank sprocket and the nose bearing all at one time....that is, together, as a pair....and HEAT the sprocket and the center of the bearing before pulling them. Do NOT even think about reusing this bearing!!
SOME will say: "When chains are changed, the front crankshaft bearing may need replacement". I SAY: ALWAYS replace that bearing!!!

NOTE!...you simply MUST protect the nose of the crankshaft!! This can be a HARDENED screw/bolt. You can purchase or make a puller. Very good pullers are available from such as Motion Industries.

NOTE!....the crankshaft sprocket, at OT (TDC), has its matching indicator line at 6:00; and the keyway will be at 9:00. At this same positioning, the camshaft sprocket has its own matching line and keyway both at 12:00, after the tensioner is in place.
***During your work; BEFORE the tensioner is in place, there will be a slight error in lining them up.***

BTW: if you replace the cam sprocket, be SURE you get the correct one for YOUR YEAR AND MODEL. BMW changed the keyway position by 3° during a change in the 1977-1978 years, which amounted to, obviously, 6° of equivalent cam-to-crankshaft change. Engines in USA bikes had this change FROM 1/1/1978. Thus, the duplex sprocket was available in two types. The timing was advanced to meet emissions rules. Some 1978 production year models did not have the emissions camshaft. I had my own way of determining which camshaft was in the bike...but, Tom Cutter posted a rather nice and easy way...and it is posted in an article on this website. The method determines, easily, if the cam is symmetrical, or not. You would not want the 1978 cam with the earlier sprocket (11-31-1-250), as it would retard cam timing. The R60/7 1976 and 1977 cams would give TDC-40-40-TDC timing when stock. The R60/7 for 1978 would give 6-34-46-6 timing when stock. The larger engines gave, when stock, in 1977, 10-50-50-10 timing...symmetrical.....whilst the 1978 would give 16-44-56-4 timing.

2. To remove the bearing separately, heat the inner race, and then pry off with two stout screwdrivers, or a generic puller.   Again, though, I recommend both bearing and sprocket together.   Once in awhile, you remove the cover, and the crank bearing just pulls off easily without any puller, heating, etc.

3. Replace BOTH the tensioner shoe and the follower shoe.   Maybe I should explain this a bit more.   pre-1979 models have a two-roller chain, called a Duplex Chain, and you WILL BE replacing the tensioner and its spring. For the 1979 and later models, they have a one-roller chain, called a Simplex Chain, and you WILL BE replacing the tensioner block unit.

4. Fit the follower shoe so it holds the chain run STRAIGHT....as seen from sprocket-to-sprocket....do NOT push it in too tight...or the chain will wear fast.

5. Besides a bearing, seal(s), cover gasket, tensioner/follower, and perhaps spring, and of course the chain, you will need to replace two (2) small round gaskets at the top of the case cover. These MUST be the same thickness as the new main gasket. MEASURE THEM.   Select them at your BMW dealer's when you go pick up these parts, that is, MEASURE them to be sure the two small gaskets are the same thickness to each other, and the SAME as the large gasket.    Failure to heed this advice will result in leaks. You can MAKE these washers, if you want to, from old gasket or other material.

6. It is critical that every teensy bit of the original gasket be removed. Use a sharp tool such as a single edge razor or Xacto knife of the needed style. NOTE: It is often not appreciated that the new gasket is specially treated. DO NOT use a sealant of any kind....or the two surfaces will 'walk...or move' over time. This is CONTRARY to some advice, yes, even advice from other 'guru's'.   If you want to, use a gasket removing chemical.   Do NOT injure the mating surfaces!!!

7.   When replacing the two seals, be sure the seal mounting surface is quite clean, and you can use a very fine grit sandpaper, cleaning afterwards, then oiling if you want to, before pushing the seal into position. The seals go flush to the surface, the alternator seal with front surface; the cam with rear surface (install that one from behind). When installing the cover you have to heat the cover again around the seal area (I've mentioned that, above). Install it well before it cools down, and install the 3 sleeve nuts and one cover bolt closest to the seal.   When the cover has cooled, center it on the cam BEFORE final tightening.             Loosen the three sleeve nuts and the one cover bolt slightly. Center the cam in its seal bore, using a caliper to measure the distance from the cam to the edge of the hole on each side...tap the cover (left-right) to center it. BMW has a tool for this, but it does not fit closely enough to do the job. Failure to do this properly will result in cam seal leaks. Sometimes there is some confusion over this heating/cooling.   The cast cover must be heated to fit over the crank bearing.

8.  The 1979 and later models had a hydraulic chain tensioner.   Just how much they helped, I am not sure.   BMW had some problems I suspect, and came out with a Service Information (bulletin) 11-014-80 (2015), entitled "Sealing Cap for Chain Tensioner Bore" which said that the sealing cap for the bore would now be punch-pricked in production; and, that any that came in to a shop for service (meaning in that area), the caps should be staked at two places.   The cap is 07-11-9-932-412, and note that the convex side (dome side) is OUT. This may be an obsolete part! This number has been checked against old fiche, and was accurate...at least in 1985!   It will be found in the parts books as an obsolete lock plug, A16.    Take a look at the photos or sketches of the main bearing holder. So, if you are in there, and yours does not have two punch pricks, add them, to ensure that they don't pop out.

9. Use Loctite BLUE on the inner stud bolts.

10. The installation of the master link plate and fish-clip can be frustrating. You may have to have a number of tries at it. Plug up the holes into the engine with clean rags.

Before getting started, some definitions:
DUPLEX chain: TWO rollers wide. BMW supplies them as endless unfortunately; but, there are aftermarket master linked ones available. Duplex chains are used before 1979.
SIMPLEX chain: ONE roller wide. Used on 1979+ Airheads, standard is masterlinked.
LINK, or MASTER LINK: A metal plate, usually in somewhat of a figure 8 shape, with two permanently affixed metal rods.
PLATE: a metal plate, usually in the same shape as the above metal plate, with holes for those two rods instead of having the rods affixed permanently.
FISH CLIP: A funny-looking clip that fits in a groove on the two rods. SOME chain link setups use SEPARATE round clips which are NOT directional.   The FISHCLIP type of fastener MUST be installed in the CORRECT direction. That direction is ALWAYS such that the rounded closed nose, is pointing in the same direction of chain travel.

Method #1: Installing the link on the rear side. This is done on SIMPLEX chains. Push some cloth into the 7:00 (+-) case hole at the cam gear area and tape over the hole.   Arrange the chain so that you have the break right there at about 7:00. Install, maybe half way or tad more, the OLD master LINK, from the front.   This will hold the chain together!   Use some sort of tool to install the link from the rear, which then pushes the old link out as the new one is pushed forward. Install the link plate and clip on the front. The engine rotates clockwise so install the open end of the fish clip pointing the other way.   Before doing anything more, double check that the crankshaft is still at OT, and that the crank and cam sprocket marks line up!   As a double check on that, when the crank is at OT, its keyway is at 9:00, the cam keyway is at 12:00, and the marks line up.

Method #2: Install the master link itself from the front. This is done on DUPLEX chains that have master links. Then put the clip in from the rear.   Try doing this at about 2:00 or 4:00 on the CAMshaft sprocket area. Some prefer 10:00. I really prefer to do this job the 'proper' way, which is #1.

No matter what you do, be sure that the tail of the fishclip (assuming you have a single piece type here...there are two-piece types......) is installed so the round nose is leading in the direction of rotation (CW facing front). If you are confused, then if the fishclip is on the left side as you face the front, the round nose of the fishclip points upwards; downwards if the fishclip is on the right side as you face the front.

There are some articles on doing timing chains on the .org website that may help you install the clip(s)...can be a PIA (Pain In the Ass), but you will do it!......the grease on screwdriver tips works nicely....so does a screwdriver magnet, etc.

11. When replacing the two seals, be sure the seal mounting surface is quite clean, and you can use a very fine grit sandpaper, cleaning afterwards, then oiling if you want to, before pushing the seal into position. The seals go flush to the surface, the alternator seal with front surface; the cam with rear surface (install that one from behind).
NOTE: The following seals information is also in other articles on this website; but is repeated here so you don't have to look. There is sometimes confusion over the alternator and camshaft seals used in the the inner cover. All models use 11-14-1-255-011 alternator seals, probably 28 x 47 x 7 mm...have not measured to confirm that size.
The camshaft seal up to models built in 9/1975 was 11-14-1-261-193. It must not be use in later models, or there will be leaks.
The later cam seal is 11-14-1-262-977, is 20 x 32 x 7 mm.

For the curious, the chain size is 3/8 x 7/32, both SIMPLEX, and, DUPLEX.

Crankshaft bearing: For many years, this was number 07-11-9-981-722, and is 35 x 62 x 9 mm. The bearing number has been changed to 07-10-1-468-882. It is a common bearing, but you must get the correct GRADE. The bearing is FAG16007-C3

HINTS!:::

    Prepare the sprocket first. Use a stone or crocus cloth to round the sharp machined edges on the ID of the sprocket so it can't hang up while being installed.
    Set the crank with the key at the 9 o'clock position, OT on flywheel will give this position, as noted. Check that you have the sprocket going on in the right direction...there is a 'step' in the ID. The larger ID goes on first, then the tighter part.
    Don't use anti-seize. Just oil the crank nose with a thin film of petroleum, not synthetic, motor oil. Heat the OILED sprocket evenly, until it JUST begins to smoke. This can be done on a hot plate, with a protective metal plate separating plate and sprocket. Do NOT overheat the sprocket, the heat treatment from the factory already has it a bit on the soft side, which is why that sprocket wears! If worried about the heating and using a thermometer, put the sprocket in a can of oil, and heat the oil on the stove. CAREFUL!!
It is important NOT to let the sprocket get over 290°F!!!
You can purchase 'sticks' that wipe a temperature sensitive coating on the sprocket. Use a 250°F type.

    Grab it with a pair of dry leather work-gloves.   As quick as you can, slip the sprocket all the way onto the oiled crank until it seats.
NOTE that you will need to ensure that the sprocket goes all the way onto the crankshaft. In order to ensure this, have ready a brass or lead hammer and some sort of sleeve made of brass. Tap the sprocket with those, right away, before the sprocket cools off. Hold it there as it cools slightly.

    Before you install the bearing, make a nice, visible timing mark with some white paint or White-Out, right on top of the faint sprocket scribe mark. You must heat the bearing with a torch from a distance, or use a close-by oven, or can of hot oil.
     If the bearing or sprocket sticks part way on, you will need a piece of sized hard pipe and a quite big hammer. Even then, you risk doing more damage than good. SO.....SO>>>...DO the job with heat and cold. Cold crank, very hot sprocket.

Heat the bearing, oiled, until it smokes....or use the same oil can method as for the sprocket...or the temperature stick. Don't exceed 290 or 300°, and use a 250°stick if using one. Put the bearing on quickly, and use the soft hammer and brass piece again.

After all the rest of the chain, tensioner's and everything else is in place, recheck that the OT mark is in the timing window, the crank and cam timing marks are lined up, and the tensioner shoe is free to move the piston in and out. The follower shoe gets LIGHTLY pressed to the chain and the nut/bolt tightened. Make sure you have the thick 8mm washers under the tensioner so it lays flat.

Earlier in this article I talked about the cover, heating it, and so on:....when replacing the cover, it is important to heat it around the crankshaft area, where the bearing fits. If you do not do this, the cover likely will not go on FULLY over the bearing....so have the cover HOT!...and the instant you have it fully over the bearing, start torqueing up the bolts!.....that means you have to center things at the cam seal too! ...but that can be done later, after the cover cools, you can loosen the bolts. Think about all this, before you start the the installation of the cover! Otherwise, you have to heat, remove the cover, and start over.

Re-read all the things on this page, again and again. Perhaps write a procedure, step by step, for yourself, highlighting just what YOU feel you need to have in writing!....as this article does jerk around some; yes, sorry, haven't fixed that yet......

Rev.
02/09/2008: incorporate all previous updates and edit some for additional clarity.

Return to Technical Index Articles Page

Return to Homepage