What follows is a pair of emails that I found tremendously informative about the rockers on most all BMW R-bikes. -RdR
Date: Thu, 25 May 95 15:46:57 EDT From: Don Eilenberger
Subject: BMW: RE: Boxer rocker arm endfloat... (longish, but good!) In which Robert Fridman answered Noemi, and I add some longish comments and ASCII artwork: >From: firstname.lastname@example.org (Robert Fridman) >Date: Wed, 24 May 1995 15:50:43 -0600 >Subject: Re: BMW: Rocker arm endfloat (G/S wrenching -- phase II complete!) > >> Every now and then I hear something or other about rocker arm >> endfloat. Looking in manuals, and at the rocker arms on my >> '81 and '83 boxers, I see nothing that would allow any freeplay >> or adjustment of the rocker arm assembly. The manuals mention >> how to test for endfloat, by jiggling the rocker arm assembly >> up and down, but mine don't move at all. The manuals also mention >> shims in the pillow blocks for engines so equipped, but aren't >> specific about how to adjust endfloat on those without shims. >> Maybe I'm just confused about what to test for. > >The rockers with the plastic washers need shims to take up the end >float. If you have end float, you need to get new shims. Feh! To >check and adjust `normal' rockers, you test rocker end float by >loosening the valve and moving the rocker up and down. Make sure you >only move it up and down and not about the axis as the push rod >would move it. I sit right in front of it and grab it with both hands >to make sure its not pivoting. I you can see oil squish out from the >rocker and pillow block, you have to much end float. True - True.. but read on... >To fix this, loosen the top head bolt about a 1/4 turn. Then use >a soft drift ( I made mine from a piece of brass) to gently and >solidly tap on the top pillow block. I hold the hammer head with >my hand (ie not the handle) to prevent the hammer from bouncing. >Give it a tap and check for squishiness. If its still there >give it another whack. If after about 2 or 3 whacks its still >loose, re-torque the top nut and loosesn the bottom one and repeat. Actually I came up with what I think is a slightly better way of doing this.. I found an old bicycle stearing head bearing ring.. (basically a 1/4" thick washer about 1.25" OD with about a 1/2" hole in it) that I place on the rocker shaft where it sticks out of the top pillow block. I then loosen the nut for this block, and put my GIANT "C" clamp on the washer and the bottom of the shaft (bad ascii art follows): /----------------------\ | | | |------------| | /----\ | | Washer----> |---| |---| | | |---|xxxx|---| | | xxxx=rocker shaft !===|xxxx|===! | | Pillow Block----> !===|xxxx|===! | | <<<< xxxx >>>> | | <<<< xxxx >>>> | | Rocker----> <<<< xxxx >>>> | | etc..etc..etc..etc..etc OTHER END !===|xxxx|===! | | !===|xxxx|===! | | |xxxx| | | ------ | | | | | | \ / | | __ / \____________| | | | |_________________________| \ / / \ <-- clamp screw 0============| |=0 <-- C-clamp adjuster ====== Now, after loosening the top head nut, you can very precisely control the force on the top pillow block - and apply controlled pressure while tightening and retorquing the top nut (which is a head bolt - gotta be torqued!) This works - done it on several other bikes besides F/C and it generally helps noise. Replacing the rocker bearings had NO effect on noise (been there - done that). >Before re-torquing the nut, make sure the rocker moves easily. >If not, then its too tight and you have to loosen it and start >again. If you use small whacks, you should be ok. As Robert mentioned - make CERTAIN the rocker moves easily, back off the adjuster and make SURE it moves - otherwise you're gonna bend pushrods (happily - have NOT been there and have NOT done that!). >Then retorque all the head nuts and set the valves. Yep! >> I ask because my R80 makes excessive valve noise on the right >> side...and before you jump in and say "noisy valves are happy >> valves," note the word "excessive!" My R65 and the left side >> of my R80 aren't that noisy. So, I wonder if there's something >> to this rocker arm endfloat thing. What sounds like rocker noise can also be cam-chain noise. On the later single row cam chain models - when it loosens up it tends to slap against the guide on the right engine side.. and the noise sounds an awful lot like a noisy valve. To test this - either use a listening stick or stethascope, or just DO the cam chain replacement (due after about 40k miles anyway). Now - for the real problem with the end-float adjustment. I measured the end float on F/C both hot and cold using 0.0005" and larger feeler gauges - and found that it changed when the engine gets hot (gets bigger) - and doesn't change uniformly. If you look at the heads - you can imagine how they will expand with heat, and see that the main head/cylinder studs (which the rocker shafts and pillow blocks go right through) will tend to move away from each other as the head expands.. opening up the clearance you've carefully set with it cold. It also has the effect of tilting the pillow blocks just slightly as it expands - meaning the clearance is not the same all they way around the pillow block to rocker arm (measure it - you'll find one spot with NO clearance, other spots with up to 0.002".. and as it changes temperature - these will change). I suspect a certain amount of noise will always be in this system.. the plastic inserts are an attempt to damp out the metal to metal noises, and adjust for the changing dimensions (plastic flows a bit - especially when warm). Other things I've done that also helped: 1. Added the rubber fin dampening blocks used on later models.. the fins if undamped tend to 'ring'. 2. Put in the new timing chain - one of my 'valve' noises went away with it (so it wasn't really a valve noise). 3. Got the carbs DEAD-ON. Last monday, I put the $100 worth of carb-rebuilding stuff in the carbs, and used Kari's trick of measuring the needle lengths. Found left needle was in slot 2 and right in slot 3. Since I suspected pinging under heavy load, both ended up in slot 3 (richer midrange). ALL sorts of noises went away. The valves sound quieter (which means they were quiet, it was other noises), the piston slap went away (which means it was actually a ping that sounded like piston slap).. all in all, I'm VERY pleased with how the engine now sounds - and I'm in summer mode - meaning no collar on my helmet, so I really hear the engine. It now just sounds better and better as I rev it, and I LIKE how it sounds > 4,500 RPM (always used to sound 'busy' - now it just sounds GOOD!), right up to redline (about 8K on the R65). This doesn't mean it isn't the end-float you're hearing - but just a few more hints to look at if this doesn't take care of the noise! Sorry for the length of the post - but couldn't resist the ASCII art. ======================================== Don Eilenberger (email@example.com ======================================== '79 R65 FrankenCycle - der Beemer '87 535i BOHICA - der Bimmer '75 Hunter 25 WindBreaker - das Boot ======================================== DOD#1177, BMW-CCA#104316, BMW-MOA#64000 NJS-BMW-R#0001 (I'm a glutton for clubs) ======================================== "Only difference between a man and a boy is the price of the toys!" ======================================== Located in lovely New Jesey! ========================================
Date: Tue, 30 May 95 08:25:46 PDT From: kimd@nit.AirTouch.COM (Kim Dromlewicz) To: firstname.lastname@example.org Subject: valve dimensions.. Roger dodger, Sorry, I thought I had posted it to you. I did post the second set of instructions and dimensions but it must only have gone to the list. (Gotta read that list). Read on and I hope this helps. Ask if there is a problem. -------------------------Original post follows-------------------- As promised yesterday I am posting the dimensions of the little jig that the Haynes manual describes. You can make one of these to align the valve rocker blocks when you are reinstalling them on the older twins. Makes for much quieter running valves and less wear and in the extreme case, damage. Metric dimensions are used as this is a metric machine we are talking about but for those of you that prefer using the old outmoded feet, inches and cubits measurements, you can convert using 1"=25.4mm. The jig is as follows: -->| |<--20mm _______________________________ | ---- | | __________|""|___________ | ___ | | | | | | ^ |__| | | |__| | | | | | | | | | 104mm | | | 8mm hole-----> |()| ----------------- | | | ^ | | | | | | | 52mm | ___ __ | | __ | | ^ | | | | | | | | | | |__________|..|___________| | _Y____Y_____ 40mm | |__| | ^ _Y_ |_______________________________| ___________Y 20mm |<---------114.5mm------->| |<---20mm |<-----------155mm------------->| The jig is placed over the blocks to square them up with respect to each other and to make them the right distance from each other before the torquing of head bolts is completed. The caliper method I use duplicates this jig though it is a little more tedious. The caliper is adjusted to the two dimensions above (114.5mm and 104mm) depending on which part of the adjustment you are doing. A repeat of the caliper method of yesterday follows: Basically, using the vernier caliper method, you place the caliper across the top two rocker support blocks and make sure they are the specified distance apart (distance to be posted as per "jig" above). Then put the caliper across and underneath the two bottom rocker support blocks and make sure they are the same distance apart as the top ones. If you are very careful and make sure the blocks are aligned with the caliper jaws as you set the distance you should have them "spaced" and "squared" pretty close to spec. Remember to leave the 4 head bolts, holding the rocker blocks, backed off SLIGHTLY so that when you tap the blocks inward or outward a little to square them up they will be able to move. Make sure you use a BRASS drift or hammer or (other soft metal) when you tap at the blocks so you won't damage them. Also remember to retorque the head bolts after. I started with the top thusly: |<----114.5mm--->| _________________________________ |__________________| | |________|============- <---vernier Caliper || ___ ___ | |---| ||| _ | | _ || | \|| _ | | _ ||/ <---------upper rocker blocks |___| |___| || || _ || || _ \ \__||__ __||__/ / \___ _ \ / __ ___/ <--------rocker _||_\_\ /_/_||_ | _ | | _ | | _ | | _ | <---------lower rocker blocks |___| |___| Then I did the bottoms thusly: ___ ___ | _ | | _ | | _ | | _ | <---------upper rocker blocks |___| |___| || || _ || || _ \ \__||__ __||__/ / \___ _ \ / __ ___/ <--------rocker _||_\_\ /_/_||_ | _ | | _ | /|| _ | | _ ||\ <---------lower rocker blocks |||___| |___|| | ||_________________| |---|________ |__________________|_|___|________|============- <---vernier Caliper |<----114.5mm--->| The vertical spacing of 104mm is done similarly for each side. The other adjustment with the "C" clamp is a way I do it also. Yesterday's posting had a "glitch" in the graphics. Today's I hope is "glitchless. Let us know how it turns out. +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Kim Dromlewicz Email: email@example.com Senior RF Engineer work: (510) 279 6200 AirTouch Communications home: (510) 672 2112 Walnut Creek, CA 94598 1972 R60/5 Black 1980 R100RT Smoke Red +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Note: The vertical dimension of 104mm on the jig is so that
the jig can be installed on the rockers, and is not the
vertical dimension associated with the rocker blocks.
There is no vertical dimension associated with the rocker
blocks, just the specification that there is no end float.
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Return to Roger's homepage .Written 16 May 1997 Last updated 21 June 2000