The New And Improved Unofficial R65 Forum V2
Technical Discussion => BMW Technical Q&A, Primarily R65 => Topic started by: steve_wicks on May 04, 2009, 04:28:39 AM
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My 81 R65 has developed a top end noise on the right pot so I took a valve cover off. Valve clearances seem okay (I don't own a feeler guage!) but I did notice a bit of float on the rocker shaft.
My Haynes manual doesn't say much about rockers apart from mentioning a special tool is needed.
But, is it likely to make a sort of loose tappet noise and why would it come loose or develope play in the rocker shaft?
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Steve, buy a set of feeler gauges :) When we are talking in the 'thou then that fraction is a lot. Set them up right and see if it cures it.
When I rebuilt the top end on mine I don't recall the rockers having any float although I will check them next friday when I reset the tappets.
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Rocker end float is the source of most of the top end noise on a boxer, unless adjusted properly.
If there is up and down play on the shaft, the rocker acts like this.
At idle the rocker has time fall down under gravity, only to have the push rod, which comes up at an angle, push the rocker up to the top of its play, before it then starts to open the valve.
IMHO this is the source of the rattling of tappets heard on most boxers
BMW eventually fixed it on the later air head boxers by using shims to control the end float.
But on the early boxers some "careful" adjustment is required for a nice quiet top end, warning, this fix involved hitting things with hammers :o
I use a socket that will fit over the rocker shaft and sit on the pillow block that the head stud goes through.
I push the rocker into the push rod, to take any play out of the rocker in rotation, and then try and move it up and down, if it moves at all I use the socket and a hammer to "tap" the pillow block towards the rocker.
I alternate between the top pillow block and the bottom one.
The goal is no perceptible free play up and down, but free to move the rocker around the shaft.
I stop when I can't feel any play, but can see the oil film moving in and out as the rocker is moved up and down.
I then set the tappet clearance, as moving the rocker up and down greatly affects the actual settings.
BTW Guzzi's don't suffer this problem as the push rod is pushing the rocker down, not up, and Guzzi fit light springs to the rockers to control the movement along the shaft.
And the early boxers didn't suffer as well, for roughly the same reason, a down side to NOT seeing the push rod tubes ::)
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You'll want to slightly loosen the nuts on those studs which hold the blocks in place to facilitate nudging them, and putting so much sideloading on those studs (which hold your cylinders & head together).
Afterwards, tighten up to correct torque in an X-pattern and recheck clearance. I just loosen the nuts about 1/2 a turn or so, to relieve some of the tension on the stud. It is generally good practice to just loosen and retorque the heads at valve adjustment time anyhow. I also recommend using the lower end of the torque spec (25 to 26 lb-feet) - don't go above this or you have some potential for pulling studs out
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It all started when I bought a new helmet and thought something had suddenly worked loose. I suppose that's why I thought it had happened over night - I'd just never heard it before because of the old helmet.
It is a relic from my car racing days and is over 10 years old, a good ole tight fitting Arai GP2 complete with nomex fireproof lining etc, but a very small slot to look out of.
As for a feeler guage, well I can't remember when I last used one, but I'll pop out a buy one although I did find a slide rule in a box of junk a year or so ago!!
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I wish I could eyeball within a thou, I wouldn't have had to waste all that money on a drawer full of mics and calipers!
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What I mean't when I said valve clearances seem okay and I don't own a feeler guage was that there was no obvious big clearance or difference between inlet or exhaust, but there was a lot of play on the inlet rocker shaft which I assumed (rightly or wrongly) shouldn't be so.
As I've said before, the Haynes manual is pretty much next to useless on this.
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Steve, You have the problem in hand, it is end play that makes most of the noise, definately get a set of feeler gauges, I doubt the slide rule would fit in the gap, but if it does, then you really do have serious end play!
Just do as they say above, loosen off the studs slightly and wack the blocks, the oil squashing bit is very important and absolutely essentilal to allow for thermal expansion. It shows there is clearence, but not much.
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I'll be doing the job tomorrow, and I have been warned to go very easy on loosening the head studs and then re-tightening them.
But, I would like to know why I've got float on the rocker shaft. Surely something has come loose, although nothing seems loose, but I haven't checked the torque on the studs yet. Should I do that before I loosen?
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I don't loosen the studs when doing the clearance adjustment, it is all "impact" driven, But I leave it up to you if to loosen or not.
As to where the increased clearance came from I have no idea, Much as I like to treat diseases rather than symptoms I will continue to treat the symptom of top end rattle with the proven fix of removing the excess clearance.
Now that I think about it, it has been my observation over the years as an engineer, that as the clearance on some oscillation system increases, the point is reached when the increasing amount of travel available will make the Joint clearance increase rapidly at some point.
This might be what has happened?
BTW, if left untreated, the bottom needle rollers will "punch" a hole through its end and all the needles will come out through the gap in the pillow block, and collect in the rocker cover, and some will make it to the sump, which means past the followers, but they seem to do this with no passing damage.
I'll be doing the job tomorrow, and I have been warned to go very easy on loosening the head studs and then re-tightening them.
But, I would like to know why I've got float on the rocker shaft. Surely something has come loose, although nothing seems loose, but I haven't checked the torque on the studs yet. Should I do that before I loosen?
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BMW also has shims in varying thickness available, I shimmed mine about 70,000 miles ago.
It has been mentioned that the shims shouldn't be used on the 'old style' rocker arms, but I have had no problems as of yet.
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I think that the blocks and the holes through which the studs pass have a certain amount of"tolerance" or slop designed in, to accommodate manufacturing variances as well as thermal expansion/contraction. I hypothesize that under many heating/cooling cycles it is possible for the blocks to "slip" slightly if the stackup of machining tolerances is right.
I like to slightly loosen the nuts on the studs so that if the surface of the block isn't perfectly parallel to the inside surface of the nut, my whacking the block down doesn't effectively "wedge" it in even tighter against the nut, which may have the effect of increasing the tension in the rod and possibly pulling a thread in the case. Since I am loosening and retorquing the nuts in the head anyways when doing a valve adjustment I don't see this as a wasted effort. To each his own - I am sure that there are better ways that I don't know about.
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So do you re-torque the heads for EVERY valve adjustment?
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The BMW manual states that the head should be torqued every time you do a valve clearance adjustment.
I don't know if this referring to backing the nuts off to zero torque then complete the 3 step torque sequence, but that is the way I've been doing it since getting the bike.
Some people claim, to just check the final torque, either the lower 25 ft/lb, or the original 29 ft/lb setting.
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Yes, I do check them each valve adjustment, per the manual. And, to get an accurate reading, you do have to back off the nuts to at least a significantly lower torque, if not "0" torque, and bring it back up. That's how I was taught, anyhow.
YMMV :)
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I personally NEVER retorque the heads unless it's after bedding in a new head gasket. I don't relish the job of putting helicoils in the block for the stud I might pull out...
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I'm with Justin, though I admit that Bob is correct in saying that the owner's manual says to re-torque them. I check the clearances, and if they haven't changed, I presume the torque is still good and nothing is happening.
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I guess that I should clarify that I don't retorque the heads unless I am changing a valve clearance. But, I haven't had much need to check them often, so whenever I have checked them I've had to make some small/minor adjustment.
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The only time I might mess with 'em on a valve adjust is if my clearance has increased... I know this is contrary to "the book"
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I didn't loosen the head/rocker nuts because I suspect the torque wrench I own might be rather inaccurate. (about 20-yrs old & never calibrated) so I tried hitting the pillar, to reduce the float, but it's the same and I really don't wan't to hit the pillar any harder.
What causes this anount of float?
I have been warned by a supposed BMW guru not to try loosen the head bolts as the stud is likely to turn in the block ..... is this true? .... he did say I should book it in for the job!!
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I think a majority of the problem with pulling the threaded studs out of the engine case is simply over torquing the nuts.
Especially if you are not the original owner of the bike, and you don't know who has worked on the bike, there are a lot of people out there, that shouldn't touching a wrench that supposedly know what they are doing .
I have seen a 'bending beam' type torque wrench used, and when the torque was checked by a 'click' type torque wrench, the torque was way high.
If you have a 'click type' torque wrench, and it's never been calibrated, you may be over or under torquing the fasteners, and you'll never know.
I bought a Snap-On torque wrench right after I got my R65, I have mine calibrated every 5 years.
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Torque wrenches should never be used to undo a nut, they are designed to work one way.
Do not be concerned if the studs looses at the crankcase end instead of the head end, it means nothing, all you are doing is slightly releasing the tension on the heads, not removing em.
crack them loose, and retighten as per the owners manual, and in sequence from the book.
If the threads are stripped in the block, they are stripped anyhow, this will not alter that, and inserts are an easy thing to do anyhow if need be.
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I have never, ever, stripped a head stud on any of the boxers I have owned or worked on.
I know it happens as I have seen the result, but can't understand how it happens.
Never had a cylinder head gasket go either, which you would think would have to be a symptom of loose head studs, even when old head gaskets are used through necessity, like on the side of the road.
No torque wrench on this "side of the road" repair either, pulled a barrel and rod after a rebuilt motor (not by me) started to knock on an Australian desert ride.
Turned out to be bead blasting residue in oil galleries killing big end bearings, but the bike was ridden home (1200 k's) as is.
But needless to say had to be re assembled.
Used the other side as a reference for head stud torque, and did it all by feel
Maybe this is why I am a fan of leaving sleeping dogs lie, and only torque when it makes sense to, like after a rebuild, but not regularly like some seem to do.
I am not against torque wrenches as such, I have three, and the little one is the one that gets most of the work.
Head gaskets are easy to replace, and no damage is usually done if fixed early, so don't sweat ti and leave things alone.
I am a Marine engineer, and I can assure you that more damage is done to equipment by "Checking" it than is caused by lack of service.
Just my opinion. ;)
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All done, head nuts re-torqued (they were all loose), valve clearances set and end float gone.
I bought a feeler gauge, but only the 4th shop had one ..... and also invested in a new torque wrench.
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The number I saw for end float was .002". I have a very large set of plyers for squeezing the ends together. Kindof a 4 handed operation.
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I use a "C" clamp and a couple of sockets...
Steve, I'm proud of you but please don't tell me you use a crescent wrench and pliers on everything else! :o
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Its nice and quiet now .....rocker covers were also the wrong way round so I put them the right way and can't believe how much more balanced the bike looks!!
Ray at Cytech advised to set valve clearances to: 0.15mm for inlet and 0.20mm for auspuf to compensate for the high temps we have here (usually!!).
Next thing is front brake as that really doesn't have much power!