Classic Valve Shim Change FAQ

by Kristian #562
Please read the Disclaimer before attempting any work in this FAQ.
Last Updated: 28 January 2007, by Winter #1935

For other related FAQs:

Introduction

This FAQ is for CHANGING the Shims after you have checked them and found them to be out of specification. For simply performing a Valve Shim Clearance check refer The Valve Check FAQ. This is a simple job you can do yourself and save some money doing it. BMW recommend the Valve Clearances are checked every 10,000km or about 6000 miles. You should change the shims when they are OUT of spec. If you are new to all this or have additional questions, it is recommended you also read the Valve Misc. FAQ.

Note that while this FAQ was primarily written with the Classic in mind, it can be used as a guide for CHANGING the Shims on Both Classic & GS/Dakar. For GS/Dakar Specific information, see the Valve Shim Adjustment GS Style part of the GS/Dakar Shim Check FAQ.

Tools

Parts

What is the Part No. of the TDC Bolt-Location Crush Washer?

Valve Shim Part # Table

mm inches BMW Part #
2.00 0.0787 11 32 1 460 147
2.05 0.0807 11 32 1 460 148
2.10 0.0827 11 32 1 460 149
2.15 0.0846 11 32 1 460 150
2.20 0.0866 11 32 1 460 151
2.25 0.0886 11 32 1 460 152
2.30 0.0906 11 32 1 460 153
2.35 0.0925 11 32 1 460 154
2.40 0.0945 11 32 1 460 155
2.45 0.0965 11 32 1 460 156
2.50 0.0984 11 32 1 460 157
2.55 0.1004 11 32 1 460 158
2.60 0.1024 11 32 1 460 159
2.65 0.1043 11 32 1 460 160
2.70 0.1063 11 32 1 460 161
2.75 0.1083 11 32 1 460 162
2.80 0.1102 11 32 1 460 163
2.85 0.1122 11 32 1 460 164
2.90 0.1142 11 32 1 460 165
2.95 0.1161 11 32 1 460 166
3.00 0.1181 11 32 1 460 167

Torques

Procedure

A. Remove Tank

Why? To access the Valve Cover.
How? See Gas Tank Removal-Replacement

B. Remove the Valve Cover
  1. When the Tank is off you faced with this: The Valve Cover. View from LHS. View from RHS
  2. Gently pull off your Spark Plug Leads and remove a Spark Plug. This will allow the Crank to be able to go a full cycle without fighting against Cylinder Compression.
  3. Removing the Valve Cover entails undoing 6# M10 Bolts. You should leave the Valve Cover attached to the Breather Pipe, put a cloth around it and tie a piece of string through a couple of the boltholes, hoist it up, removing it out from the LHS Side of the Bike and over your handlebars and tie it firmly in place, out of your way. Don't twist the Breather Pipe Hose (let it rotate at the Valve cover if possible) if it's an older pipe and brittle, it may break. The OEM clamp holding the cover vent to the vent hose is non-reusable, so if you do take it off have a spare (small, about 10-12mm) hose clamp handy to replace it. You CAN get those OEM clamps back on, but it's not easy and not always as tight as when you take them off. Bottom line is you don't need to remove it.
  4. The Cams and underneath them, the Shims, will be exposed.

    The bike MUST be cold, even after 4 hours I got a 0.01mm difference when compared to leaving it overnight and checking it again.

C. Re-checking Current Clearances
  1. It is highly recommended that you check to see if the current clearances are in fact within or out of specification. if you haven't checked your Valves before refer the Valve Shim Check FAQ before trying to change your Shims.

    Valve Clearance Specification - Classic:

    The "Classic" BMW Manual specifies:
    0.10mm ~ 0.15mm or 0.004" ~ 0.006"
    for Both Intake & Exhaust

  2. Re-measuring the current clearances:

D. Determining the new Shim Sizes
  1. Note the nomenclature here. When talking tight or loose clearances we talk about what you actually measure, NOT what the Valve is in doing in the head.
  2. OK, you've checked your Valve Clearances and some of them are out of spec. How do you know what to replace them with. You know the clearance and you know it must be either increased or decreased, but without knowing the current shim size how do you know which way to go and which ones to buy? The answer is if you haven't already done this job once and taken a RECORD of what's in there now, you don't know. I do not know for a fact, but I very much doubt the same shim sizes were put in at the factory for every bike.
  3. If you are at the lower end of the range, i.e. 0.10mm, (Tight Clearances) Flash recommends leaving it to see which way they go. Other Chain Gang members have been told by their dealers loose is better than tight, as the clearances very often, but not always, decrease as the valves seat with wear. It is advisable however, not to wait another 6000 miles to check, or a burned (exhaust) valve may result.
  4. Johnathan #145 notes "You want them tight for better performance, however, on the F650 too tight can and will get you into trouble with wear on the cams. At least on the carbed engine. For the new GS, this isn't the case because the cams in the FI engine are made of a better quality metal than the carbed version. The cams (and I believe the head Ed.) are the only parts that Rotax does not make the for the FI engine." Please note I only put this in inverted commas as I cannot easily verify this information.
  5. One of the additional reasons to avoid too tight (i.e. < 0.10mm) exhaust clearances is the possibility of damage by overheating (burning) an exhaust valve. This occurs because the valve is actually open more/longer and contacting the cylinder head less and is therefore unable to cool properly by heat transfer to the valve seat in the water cooled head. (The camshaft quality problem is rumoured to only affect some bikes across one and a half model years, '96~'97~'98.) So for an exhaust valve, if it is unlikely to be checked for another 6k miles, stick with 0.155mm rather than go to 0.105mm and risk wearing down past 0.10mm. For most people, longevity of the engine is more than worth a slight loss in power.
  6. Now various dealers and after market parts places will sell you either individual shims, to sizes you specify, or a block of commonly used Shims of various thickness. You'll normally find it'll be one of those. The shims come in increments of 0.05mm. Alternatively you have to take OFF the Cam Carrier (See Section E below) and remove the current shims and beg, steal or borrow a micrometer and measure the current size, so then you can go back to the dealer and tell him which sizes you want. Note that a cheap US$7 Micrometer will be able to tell the difference between 2.40mm & 2.45mm, so treat yourself.
  7. Note that you can also use the Shims that are currently in the bike in another location that needs the Shim size you currently have, if you didn't get the right replacement sizes and you want to get the bike back on the road. This means it is possible to replace just one of the Shims and swap some of the other ones around, depending on the sizes you need. The Shims themselves don't really wear "out" (of course there is some wear), so don't think of it as "renewing" your shims. What happens is the Valve Seats get worn, because this is where all the hot action is, literally, particularly the exhaust Valves. However, the Shims are not really that expensive and while it's probably OK, certainly it's OK in an emergency, in higher mileage applications and on other types of engines, Shims have exhibited wear patterns. At 6k miles, probably not a problem. At a greater mileage, probably inadvisable. They're pretty cheap, so it is advisable to buy a few extra and you will then also have some spares for future valve adjustments.

Note:

E. Taking off the Camshaft Carrier
  1. OK, you've determined you need to change the Shims and you need to know the sizes currently in the bike or you have your new shims and just need to change them. To do this you need to remove the Camshaft carrier, which is the frame which holds the Two Camshafts in Place like a Sandwich, then lift the Cams up (in the frame) enough so that you can get to the shims and remove them. You do NOT need to take the Cam Driving Gears off the Cam Shafts and you do NOT need to remove the Camshafts completely from the Camshaft Carrier.
  2. STUFF SOME RAGS IN ALL PLACES, ESPECIALLY AROUND THE CAM CHAIN, WHERE SMALL BITS, SHIMS, TOOLS ETC CAN FALL DOWN!
  3. First you need to be able to get the Cam Chain loose enough to lift up the Cam Carrier enough to get to the Shims. To do this you need to undo the Chain Tensioner, (Chain Tensioner Bolt Location) accessed from the LHS of the bike at the back side of the engine. There is a large 22mm Bolt. Undo this bolt. Note the Crush Washer should be replaced when reinstalling. It is the same size as the Oil Drain Plug Crush Washer, or at least that washer fits, so if you have a spare one of those you could be in luck. Behind the bolt is a Steel Cylinder, which is the "Hydraulic Tensioner" itself. The steel cylinder pushes up against the Chain Tensioner Guide under OIL PRESSURE. The BMW service manual "Engine Oil Circuit" diagram shows the chain tensioner as shown as being fed off the high pressure oil line. So it only tensions when the Engine is running. Elsewhere in the manual it's described as a "Hydraulic Chain Tensioner". Remove this cylinder so it doesn't drop onto the ground and score the sides of the cylinder.

    Note that you can UNDO the Chain Tensioner Bolt with a ring spanner, but the darn Carbs can get in the in the way for torquing it up. Here's a recommendation:

    "With a new washer, and using recommended sealer (e.g. Yamabond as a substitute for ThreeBond 1209 on the washer), I just do mine by hand. Gingerly. I can't see that setup withstanding 40Nm forever. I think I can get a small torque wrench in there with some strange adapters, but it only goes to 30Nm, which is plenty as far as I'm concerned. You can easily tell if it leaks - looks like a good candidate for drilling and safety wire to me, good washer and sealer, and forget the 40Nm." Hombre sin Nombre. See Where can I get Optimoly MP3, Loctite 243 etc. Are there any Substitutes?
  4. At this stage I highly recommend tying the Cam Chain to Gear wheels with some zip-ties.

    IF YOU WANT TO CHECK YOUR CAM BEARINGS AT THE SAME, you CAN remove the Black Plastic T-Piece in between the Timing Gear Wheels, however this is NOT Necessary. These two bolts tie the Upper Frame and Lower Frame Together, and if you don't remove it the Cams can be lifted with the Cam Carrier, as one unit, at least enough to access the Shims. See here for a picture of the T-Bone Spacer. (Note Marks not lined up in this Photo)
  5. If you want to you can take the chain off the Cam Driving Gears, but it is NOT necessary and the advantage of leaving the chain on the gears, (and tying them to the Gear wheels with some zip-ties) is that your chain doesn't move with respect to the Gears. If you do decide to take them off to have a really good look around in there, MARK the position of the Chain with respect to the Gear Wheels so you know where they go back. Also MARK which Cam (with Gear Wheel attached) is the front (Exhaust) and which is the rear (Intake). If you do take the chain off, tie a piece of string onto it first, and tie the free end to the handlebars. Be careful you don't accidentally drop the chain into the Cam-chain Well.
  6. You can also remove the FRONT Black Plastic Chain Guide (Don't try and take out the Rear one) by just GENTLY pulling it upwards and slightly backwards. This will loosen the chain some more and let you really get the Cam Carrier up. See here for what it looks like when it's out: Front Chain Guide.
  7. Note that The rear cam chain guide rail has a bolt stuck through it at the bottom and will NOT pull out.
  8. At this Stage I highly recommend putting a Large Cloth in the Cam Chain Well so you don't drop anything (like the Shims) into this well. Not a good idea.
    Hint for removing the cam carrier
    A word of caution---Even though I had a rag stuffed down in beside the cam chain, [the washer from the cam carrier bolt] still made it's way down there. I would advise not pulling the bolts out of the cam carrier but loosen them until they are free of the head and then pull the entire cam carrier and bolts out as one unit. Return them the same way. Maybe it will save you this pleasure. jagdkampf #1761
  9. Remove the Camshaft Carrier. It has 8 Allen-Head Key Bolts in it. Check you have a Torque Wrench and Allen Key Socket that has a low enough combined height to fit under the Frame of the bike for when you go and torque them up. The frame is actually in two parts, a lower and an upper frame, but as they are tied together by the T-bone, they will come out as one unit. Loosening the bolts undoes both in any case. Lift up the entire frame and prop with a wooden block, to access the Shims.
  10. If you took out the black plastic T-Bone, you can lift off the upper frame only. The lower carrier can remain in place. This will give you access to the Cams, which you can now lift up and prop in the air with a Wooden Block, just enough to get the Shims out.

F. Removing the Shims
  1. The Shims sit in Shim Buckets, (like an upside-down bucket) which fit over the Valve Stems & Springs. They look like little silver coins and are around 2.5mm thick, to give you an idea of the size. The Shims sit in a small well on the top of the upturned Buckets, with two little slots on the top and close to the edge of the Bucket. The Buckets can be easily rotated to give you better access to the little slots. Don't worry you are not unscrewing them or anything!
  2. Using either a very small screwdriver, a toothpick or some other small and thin object gently prise the shim out of the well, gaining access via the slots. It is held in place only by Oil Suction, and when prised free comes out easily. Do one at a time and take care you don't drop it anywhere into the engine. See tip above about cloths.
  3. Clean, measure and/or mark each one with thickness and/or the Shim location, so you know where it came from, in case you don't have a micrometer but do know the old thickness. Make sure they are clean and free from specks of sand or grit before you pop them back on. Some people use surgical gloves.
Johnny K Note
"I found that even with some nicely sharpened tools it was tough to budge the shims with the buckets in place, due to oil surface tension/suction. However, if I raised the bucket 1/2" or so, whatever that space is that's available below the raised camshaft assembly, I could then push upwards on the shim edge and it pops right out. Another advantage is that with the shim and bucket in contact with the cam assembly, the freed shim is less likely to flip out into the sump. Took your advice about the rag stuffing too though. There is no way to get even the skinniest prying utensil under the shim if it's fully in the bucket. The space in there clearly is deeper than the slots. So when you pry you are really just pushing with friction against the side of the shim. That's why it helped to have the bucket up so I could be pushing upwards against it, I assume. I also noted as you suggested in the notes that the new clearance should only be measured after turning the engine over a full rev. The oil on the new shim must be forced out and off before the reading will be accurate. I discovered too that the shims from 2.25 to 2.75 (that diameter) are pretty common in the mc world. Since a BMW dealer is a ways off, I tried a guy locally who builds Rotax race engines for track racers. He had a whole assortment of shims that were Yamaha that he uses. I just swapped mine for one of his." (Thanks, Johnny K).
Werner #547 Note
The rag works well, as Flash says. But you can be doubly sure by lifting out the whole cup holding the disk. (Do one at a time, so as not to mix them up during reassembly). Then you can sit down on your barstool and remove the little disk with your pointed nail while sucking on a tall bubbly.

G. Replacing the Shims
  1. Well, from "D" above, by now you should have been able to calculate which shim should go where to be in spec. So pop them back in at the correct location. As far as I know there is no correct way up, although I would say if you can see a smooth side, face that up.
  2. It is a good idea to wet everything with oil (both sides of the shims) during reassembly.

H. Replacing the Cams/Carrier/Chain/Chain Tensioner/Tank
  1. If you took out the T-bone Spacer, before you replace the Cams in the lower carrier, make sure the lobes are nice and clean. Inspect the Lobes (and Cam Bearings if you took the Cams out of the Carrier) for pits, marring or flaking. Note this is a warranty item if found. Each CAM runs about $375. Make sure both the Cam lobes and the Cam Carrier bearings are nice and clean. Replace the Upper Frame.
  2. Make sure the new shim (or opened cam bearing) and the cams and bearings are well coated with oil for installation - they should not be installed dry and left dry, as it will take several engine cycles for the oil pressure to reach them. The cams and buckets can be slathered as they are re-installed or just before the valve cover goes on, but the cam bearings should be wet with oil when re-installed.
  3. Replace the Cam Carrier, checking the timing marks still line up on the Gear Wheels Timing Marks. (They should do if you zip tied the chain to them!). Check the Cam Gears are able to be toggled and are not pinched, then Torque them up. The Torque value is 10N.m. Check you can Toggle the Cam Gears once again. The Manual also says to tighten the Camshaft Carriers from the inside out. The inside is the flatter, less pointy end of the Cam Lobes as they are at TDC. Tighten once by hand lightly, or to 5Nm, then finish with 10Nm.
  4. Don't worry if when you put the Cams back, the timing marks are out, it is possible to lower the chain far enough so that it disengages from the drive gear at the bottom end (i.e. in the Crankcase) and goes along one tooth, as long as you STILL have the TDC bolt in place. You can simply cut the zip ties and put the Cams back WITH the marks on the Cam Wheels aligned WITH the lobes outward.
  5. Note: It is very difficult to properly access the rearmost RHS bolt with a 3/4" drive torque wrench and a 3/4" tool bit as it is just too high and just won't fit between the frame and the Bolt. I made up a 1/4" drive, 5mm bit for a 1/4" drive torque wrench. See (picture) Otherwise that last bolt must be torqued by feel, based on the torque you put into the other 7, so do a few of the other 7 first to get a feel for it.
  6. If you took it off, replace the black plastic T-Bone Spacer. Only do this after you Torque the Carrier Bolts and use Loctite 243 on these bolts.
  7. Replace the long black plastic Cam-Chain Tensioner Guide by feeding it in behind the chain (at the Rear of the well), keeping it close to the face of the well, until it engages at the bottom of the well. Make sure it's properly seated.
  8. Reinsert the Chain Tensioner Cylinder, giving it a squirt of oil before you feed it in, followed by the Large Bolt (complete with new Crush Washer). Torque Bolt to Spec. (40Nm). The manual also recommends using ThreeBond1209 or Yamabond on the washer. Be careful to NOT exceed 40Nm torque as it seems an excessive amount of torque on such a thin and delicate portion of the engine. Be careful NOT to put too much of any silicone-based sealer anywhere, e.g. threads as it can get into and clog thin oil passages. See Where can I get Optimoly MP3, Loctite 243 etc. Are there any Substitutes? for a more detailed explanation.
  9. Note: The Chain Tensioner cylinder is a miniature hydraulic cylinder, acting as a self adjusting spring on the cam chain guide, pressurized by the engine oil pressure. If its tiny check valve is leaking slightly, it will reseat and allow you to install the Large Bolt easily. If it's not leaking, it may seem too long to re-insert and install the Large Bolt. You must de-pressurize it by looking in the opening, finding the tiny ball bearing check valve, and pressing it open with a pin to allow oil to leak out. This will allow it to shorten enough to install the Large Bolt. If you think you have a problem with noise from a loose cam chain, especially at start-up or low oil pressure, or find wear on the chain guides, this is one of the parts to consider replacing.
  10. Give the Cams, Bearings, Shims and Cam-Chain a squirt of oil, check you haven't left anything in there that there shouldn't be there. Use a flashlight! Make sure no bolts are loose.
  11. After installing new shims and tightening the cam carriers/tensioner, but before installing the valve cover, it's worth taking out the TDC locating screw and rotating the engine by hand a few times, with the Socket in the Flywheel, just to see if everything is right. This is the important part, to spin the motor around at least two revolutions, maybe four, and measure again before you button it back up. (The oil film will take up some of the clearance until you spin the motor to squish it out.) It is a REALLY good idea to re-measure the clearances also, just to make sure. It's better than finding out at start-up that it was re-assembled 180 degrees off. Do not worry if they are not exactly what you calculated!. Close but not exact. The difference is mostly in the Oil Film.
  12. Check the Seal Surface of the Valve cover is clean, Check the seal is in its groove, Replace the Valve Cover, Torque the bolts to 10Nm.
  13. Replace the Tank. See Gas Tank Removal-Replacement

That's it. Ride off (into the Sunset) and Ride Safe. Go home, have a few beers with the money you just saved, and feel very very satisfied.

Time

Lots of Leeway here. You should be able to do it much faster.

See also these beautiful photos of the Valve Shim Replacement Valve Adjustment Photos from Jim Powell. Jim also likes to be called John :-) and likes cars (blah!) with 400HP!
Note in Jim's Photos, the Timing is off one tooth!

Many thanks to Flash, Richard, Todd, Marty436 & Johnathan Gifford, for all their very constructive comments which are reflected in the FAQ.