The New And Improved Unofficial R65 Forum V2
Technical Discussion => BMW Technical Q&A, Primarily R65 => Topic started by: quixotic on June 11, 2014, 08:24:02 PM
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I think I might give it a try...especially after picking up the Haynes manual and seeing how easy it is to take out the con rods. Initially, I'd just do the con rods and the pistons. Then, if I wasn't satisfied, I'd do the flywheel. Then, possibly the crankshaft.
Has anyone done any of these? Any improvements as a result?
One thing that has been puzzling me is why would vibration only affect a certain rpm range? Intuitively, I would think that if some engine part was out of balance, then the whole rpm range would be affected. But obviously I'm missing something obvious (wouldn't be the 1st time [smiley=beehive.gif])
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I once inquired of Bob's BMW about having Msbuck's '84 R65 engine balanced because she wanted to get rid of the 4000 rpm vibration. I was told by their machine shop that they had never done a balance job on an R65 because "no one ever wanted to spend that kind of money on an R65". I was also advised that not even the larger engines responded 100% to the process.
At the time I was warranty manager at a BMW dealership and had good connections with BMWNA tech guys. They advised first to loosen all engine mounts and retighten as uniformly as possible. Also suggested to check owners manual to see if the carb needle positions were correct. Some owners had received notification and a sticker to put in their manual to move the needle up a position. They strongly advised against using the rubber grommets some folks were putting on the engine mounts as this could cause the frame to crack.
Bottom line is that nothing has eliminated the vibration totally but Msbuck says after 22 years she has just gotten used to it!
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Has anyone done any of these? Any improvements as a result?
Yes and No is my answer.
you may recall that a few months ago I pointed out how easy it is to balance the reciprocating parts of our R65s, just make a beam balance and balance up like for like.
Will you feel a difference worth the effort - I doubt it. Like wise you can spend a fortune and have the crank, flywheel (sorry Clutch carrier) and clutch all balanced up and I still doubt you will feel any difference. The reason is that the primary source of vibration in a boxer twin is the rocking couple of the UN-counterweighted big ends. The rocking couple can set up harmonic vibration in the frame which for some reason seems to bedevil the R65 more than any other model.
The other source of high speed vibration - about which you can do nothing by the way, is flex of the crank shaft.
BMW's own investigation into crank flex (which first became a real issue in the R90s) was to decided that they could not do anything about it and sole response was to increase the internal clearance of the alternator rotor to stator. I have seen a film of a R90 engine that had the crankcase "windowed" and the crank painted with a fluorescent dye which was when running photographed using a xenon strobe as a light source.
The amount of whip in the crank was initially quite sobering until I recalled that the streets were not littered with BMW twins with broken cranks (in fact I have never heard of one breaking in normal service) and after my own R100 passed the 200,000km mark I kind of decided that BMW's view of the world, namely to simply provide enough clearance to allow the crank to flex without rubbing anyhting, was the right one.
But, the crank flex is also a source of vibration about which you can do nothing. I've never held an R65 crank next to a R75/80/90/100 one, but I suspect that the R65 crank is probably stronger by virtue of the shorter webs whilst retaining pretty much the same diameters everywhere.
If you get the idea that I think that there is little useful you can do about the particular vibration in BMW airheads, you are right.
I do however think that the idea of loosening all the engine mounts and then carefully bringing them all up to the same torque is a good one.
I discount the assertion that cone couplers are a bad idea. Firstly BMW fitted them as OEM eventually and secondly, I haven't seen too many airheads parked by the side of the road with cracked frames (cracked sub-frames yet, but that is a cat of a different colour).
I have ridden R65s with and without aftermarket cone couplers and mty own r65 has them OEM. My opinion can be summed up as "if my BMW didn't all ready have them, or if I had all the spacers handy to dispense with them, I wouldn't bother, but I don't have the spacers and the couplers were available within 5 minutes of my office, so the couplers stay.
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One thing that has been puzzling me is why would vibration only affect a certain rpm range?Intuitively, I would think that if some engine part was out of balance, then the whole rpm range would be affected.But obviously I'm missing something obvious
Any mechanical system will have a point of resonance which is the natural frequency at which the amplitude of vibration reaches a maximum. Clever design tries to put that frequency out of the normal range of use. Sometimes they don't succeed think Tacoma bridge.
Ours happens to be somewhere in the region of 5000 RPM although it can be reduced/moved up the rev range a little by changing the coupling with the frame by aftermarket rubber mounts or to some extent by changing engine mounting torque settings.
The interesting question- is it the engine that has a resonant frequency at 5000 RPM or is it the engine frame combination. If as Tony suggests it's the latter then your supposition that engine vibration levels should be of the same amplitude throughout the rev range may be broadly correct and it's the frame that is resonating. I wonder if anyone that has done frame strengthening on an R65 has noticed a change in vibration levels.
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The only thing I had balanced was my 1979 R65 was the flywheel (heavy), which was done as a part of a lightening exercise. Not a great deal of material taken off, as I had a strict budget, but I felt that there was some improvement. Not that my 1979 bike suffered much from the 5000rpm vibe in the first place. But then it was well run in (at circa 100,000 miles) by that time.
Interestingly enough, my R100 has developed vibration, now that I am changing its configuration. Removal and redistribution of weight in general, changing the handle bars (alloy renthal type things) and sub frame, etc, has now give me tingly hands after a long ride at speed.
I am considering replacing the light alloy handlebars with a set of Honda Hornet steel bars that I have, which have bar end weights. Trouble is the weight are designed to dampen the vibes from a 600cc 4 cylinder inline, not a 1000cc flat twin.
Something I am now going to have to look into further as I have not finished removing weight....Centre stand goes next, followed by anything else I can remove.
So I am also coming down on the engine/frame/cycle parts interaction, rather than blaming the engine alone.
Cheers
Steve Hawkins
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Thanks for the responses everyone. This is getting curiouser and curiouser. I'll have to check with the Motorrad specialist in Calgary, who is currently doing some balancing stuff for an R45.
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Here's a fascinating thread on the subject:
http://www.advrider.com/forums/showthread.php?t=420346
I like this quote:
"It was weird revving the engine. I'd hear the noise, the bike would lean to the right, but I couldn't feel ANY vibration. Seriously, it was hard to tell the bike was running."
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I replaced the metal spacers between engine and frame on my '84 about 10 years ago with hard rubber spacers I made up myself. My frame is just fine, and the harmonic between 4500 rpm and 5000 rpm was eliminated completely. I replaced the rubber spacers once already, just as a maintenance, and I will probably do it again in a couple of years.
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I replaced those metal front spacers with home made rubber spacers and there is a big difference. I am planning to change the rear ones too, just to see what happens.
A couple months ago, when I took my R50/5 engine out of the frame, I noticed that the spacers were made of aluminum, which is softer than steel. It might be to reduce the vibrations getting to the frame.
Just try putting some hard rubber spacers in there to see if it helps, make sure your carbs are well balanced with new slide needles.
Brand new needles made the bike smoother in my case.
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I replaced those metal front spacers with home made rubber spacers and there is a big difference.
What did you make them out of? Can I just carve up a chunk of engine mount material from a car?
Given what Barry said above, rubber spacers might even mean that engine balancing would be worthless (ie, if the major issue was frame harmonics).
Would the R65 frame really be that different from the old slash/5 frames? (I used to have a toaster, and I don't recall any rpm bands of vibration that ever stood out).
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So the lack of vibration in the R65 Mono would be just down to the frame and not anything BMW did with the engine ?
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I used sway bar bushings which looked like this that are listed on ebay.
http://www.ebay.com/itm/Moog-K7275-Sway-Bar-End-Link-Thermoplastic-Bushings-/390862680049?pt=Motors_Car_Truck_Parts_Accessories&hash=item5b013b2ff1&vxp=mtr
I am not sure what car they were for. Basically any solid hard rubber should do it. You might have to size them using a simple bench grinder and a couple of thin cup washers on both side. I think I posted a picture on here a few months back. Hope this helps.
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Given what Barry said above, rubber spacers might even mean that engine balancing would be worthless (ie, if the major issue was frame harmonics).
Would the R65 frame really be that different from the old slash/5 frames? (I used to have a toaster, and I don't recall any rpm bands of vibration that ever stood out)
So the lack of vibration in the R65 Mono would be just down to the frame and not anything BMW did with the engine ?
What I was saying is it's the way the engine couples with the frame that might make a difference to how the engine and frame vibrate together. It's not as if the rubber bushes totally isolate the engine as there is still metal to metal contact but there is enough difference to change the coupling. The frame may have harmonics but it still has be excited by the engine vibrations so a smoother engine is always going to help.
On the mono's besides a different frame the only thing I know that's different is substantially (something like 40%) lower torque settings on the engine mounts which again may change the way the engine couples with the frame.
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I used sway bar bushings which looked like this that are listed on ebay.
http://www.ebay.com/itm/Moog-K7275-Sway-Bar-End-Link-Thermoplastic-Bushings-/390862680049?pt=Motors_Car_Truck_Parts_Accessories&hash=item5b013b2ff1&vxp=mtr
Thanks for that info. I think I'll get these from Princess Auto:
http://www.princessauto.com/pal/en/Accessories/Sway-Bar-End-Link-Bushings/8449373.p
I didn't have any luck finding cone washers, so hopefully the ones shown in the photo would work.
Would blue locktite be sufficient to keep the nuts on? There's not much extra thread to work with, so maybe I should put a couple extra nuts on there with locktite, in addition to the original nuts tightened to 12 foot/lbs.
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The jam nuts should really have all their threads engaged. Then they can be snugged down nicely.
If you can't get jam nuts all the way onto the stud, I wouldn't trust threadlocker. I'd probably go for nylock main nuts or drill the stud to accept castle nuts and cotter pins... but that could mess around with getting the torque "just so."
Btw, I wouldn't consider split lock washers for fear that they'd crack.
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The jam nuts should really have all their threads engaged. Then they can be snugged down nicely.
If you can't get jam nuts all the way onto the stud, I wouldn't trust threadlocker. I'd probably go for nylock main nuts or drill the stud to accept castle nuts and cotter pins... but that could mess around with getting the torque "just so."
Btw, I wouldn't consider split lock washers for fear that they'd crack.
I just had a closer look at it, and there are existing lock washers on both sides. So if I take those off, I think there will be ample thread for the two torquing nuts, as well as the two locking nuts (and some locktite just for added insurance).
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I think they're wave washers, though, not split lock washers. You should have a washer between the first nut and the frame.
IMO a nylock nut and wave washer would probably be a good way to start, with some frequent checks and tools under the seat.
I seem to recall hearing that the old vibration damping kits came with longer engine mount studs.
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Wow! It worked! I gotta admit that I was a bit skeptical at first. But now the 4,000 to 5,000 rpm range is a smooth as butter. There's a minor little buzz around 4,000, but it's in a very narrow rpm range and I can easily live with it.
I used the sway bar bushings from Princess Auto (mentioned above). I just reamed out their holes a bit and cut them in half, so that each half was about 7mm's thick. I then inserted them in some 1/4 inch chunks of teflon, so that they wouldn't get compressed out of shape.
I couldn't find the cupped washers anywhere, so if anyone has a link, that'd be great. I'm not terribly confident about the long-term viability of the teflon, so I think I'll shortly re-do the housings with chunks of aluminum.
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If the auto parts counter guy is willing, look through a few boxes of random sway/torsion bar end links since many of them are equipped with cup washers. They're surprisingly inexpensive. I think I got sets from O'reilly auto for a 2005 Chevy Astro. I got these last year to mount 10hp Briggs engine to a log splitter. An old engine that was vibrating badly enough to crack welds and these worked a charm.
I'm encouraged by your feedback. I may just have to try this. With the torque and radial loads imposed on these bearing a Boxer I might be more inclined to go for the more rigid and dense red urethane versions. These parts were designed, at the mounted ends of sway bars, to bear axial load primarily (if I correctly recall the distinction between those two).
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If the auto parts counter guy is willing, look through a few boxes of random sway/torsion bar end links since many of them are equipped with cup washers.
There were cup washers included with the sway bar end link kit I have, but they are each about 2mm thick (at least). So there wouldn't be any room left for rubber.
With the torque and radial loads imposed on these bearing a Boxer I might be more inclined to go for the more rigid and dense red urethane versions. These parts were designed, at the mounted ends of sway bars, to bear axial load primarily (if I correctly recall the distinction between those two).
I might try that also, since even with 12 foot/lbs of torque, a small amount of the black rubber had a tendency to sqeeze out from its enclosure.
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Here are the aluminum/polyurethane washers I made. Both materials were quite easy to work with. The aluminum (2 x 1/8" bands) is easy to cut even with a ten dollar coping saw. The polyurethane is easy to cut with box cutters and/or the coping saw. The poly is almost 8mm's thick, so I did some minor shaving where the unit needs to slide between the frame and the engine (a dab of grease helped also), and also where the big bolt needs to be drifted through. I also had to cut off another couple of mm's of aluminum for the right side, where it would have otherwise interfered with the oil filter cover.
For the vibration alleviation, it seems to work almost as well as the teflon. Not perfect, since I suspect that the aluminum transmits a bit of vibration. But nonetheless a vast improvement for mere pennies. Now I can cruise at the speed limit (110 kph), instead of having to choose between 100 or 125.
Glad I changed the teflon out. The data sheets for it show that tensile strength is reduced more than 90% at 150 degrees fahrenheit.
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Here are the possible best fit cup washers that would be perfect for this job. Very thin and almost correct size. Take a look at this listing. You just need those washers and nothing else. Would be nice to find those at a BMW dealer or Motobins?
http://www.ebay.com/itm/BMW-Airhead-R60-R75-R90-6-Medium-Height-Speedometer-Bracket-and-Hardware-/221490003701?pt=Motorcycles_Parts_Accessories&hash=item3391d53ef5&vxp=mtr
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Here's the latest iteration. A sandwich with a 1.5mm thick washer on both sides and a chunk of polyurethane 3mm's thick in the middle. And then a 6mm slice of aluminum tubing (17/16th's inch ID approx) to keep the poly from squeezing out. The tubing extends far enough out to minimize engine to frame contact, and the washers were ground down so that they were just a tad smaller than the ID of the tubing. So the theory is that the engine pushes on one washer and the frame pushes on the other, and the poly in between absorbs any vibration.
It seems to work fairly well. At least as well as the set-up that I initially tried with the teflon. Whereas with the stock washers, the vibration band was about 1,000 rpm wide, the vibration band is now less than 200 rpm wide.
The biggest hassle turned out to be grinding down the washers with an angle grinder. It would've been nice to find something off the shelf which fit nicely inside the tubing. However, even just finding a large washer that's sturdy and also only 1.5mm's thick might be the difficult part.
Now I'm curious about teflon, and whether a simple 6mm wide washer made out of it might work. I don't know if it would absorb vibration, and I don't know if it would survive the heat. Does anyone happen to know how hot the exterior surface of the sump gets up to?
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Here are the possible best fit cup washers that would be perfect for this job. Very thin and almost correct size. Take a look at this listing. You just need those washers and nothing else. Would be nice to find those at a BMW dealer or Motobins?
http://www.ebay.com/itm/BMW-Airhead-R60-R75-R90-6-Medium-Height-Speedometer-Bracket-and-Hardware-/221490003701?pt=Motorcycles_Parts_Accessories&hash=item3391d53ef5&vxp=mtr
Do you know if there are four cup washers included there? I'm mighty tempted to order that unit.
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quixotic, the last picture of what you have made, is just about a duplicate of the Luftmeister vibration isolators .
About the only difference, is that the Luftmeister parts were all bonded together .
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Now I'm curious about teflon, and whether a simple 6mm wide washer made out of it might work.I don't know if it would absorb vibration, and I don't know if it would survive the heat.
Teflon would have no problem at all with the heat.
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For what it's worth here is another opinion.
http://www.nebcom.com/noemi/moto/r65faq.html#ENGINE_VIBRATION
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I didn't realize this link on "engine vibration" would transfer all of the blog. But it's all good stuff. So, enjoy.
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Now I'm curious about teflon, and whether a simple 6mm wide washer made out of it might work.I don't know if it would absorb vibration, and I don't know if it would survive the heat.
Teflon would have no problem at all with the heat.
I've mistakenly been using teflon and what I've got (UHMW plastic) interchangeably. But they're quite different...especially with regard to heat.
http://www.articletrader.com/computers/software/uhmw-sheets-versus-teflon-ptfe-sheets.html
Maybe I'll try to track down some of the former:
http://www.walmart.com/ip/Teflon-Pressing-Sheet-18-x-18/17337950
But something tells me that it would likely still transmit vibration (or else Luftmeister would've already tried it).
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quixotic, the last picture of what you have made, is just about a duplicate of the Luftmeister vibration isolators .
About the only difference, is that the Luftmeister parts were all bonded together .
Does you know if the Luftmeisters were designed to be used on all four engine mounts? Or just the front two?
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Well, I finally got around to trying this on the rear mounts as well. I used a 6mm deep slice of aluminium tubing (22mm ID) filled with an 8mm thick doughnut of the tie rod polyurethane material. You can see it in the photo where the poly has been forced out by the 12 foot/lbs of torque on the engine mount nuts. You can also see where I added on an old Miata wheel lug nut with blue loctite to keep everything in place. And then to give me enough threads for the lug-nuts (probably less than 8), I repositioned the exhaust pipe hanger to the foot peg bolt.
Wow! Even when I kept the bike at 4,000 to 4,100 rpm steady (the worst area of vibration remaining after I did the front mounts), I couldn't detect any vibration. Smooth as silk all the way up the rev band.
I guess the only question is how long will it last? There's the question of the tensile strength of the aluminum, as well as the possibility of more poly being squeezed out. But I'm happy for now. :D
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My Mono doesn't...or didn't vibrate. However I've just been into the gearbox to do a broken pawl spring, and a few other things you have to as a matter of course on such a job. At a 100,000km I also had a look at the clutch. I could see the white paint marks, so thought sweet, factory markings I'm good to go. But putting it back together a couple of weeks later I find only 2 of the 3 elements are marked, the pressure plate which sits behind the cover plate has no mark. And also I can't get the 2 marks I do have at 120 degrees...the next bolt holes around, but no way are the white marks 120 degrees.
So now I have a slight vibration at 5,000rpm - all good everywhere else in the rev range, but just a noticable amount at 5,000. Far less than an LS I've ridden, but more than it had before. The clutch is down to 5mm, so I should have at least 30,000km left on it...3 years commuting. I'll give it a few months, or until it annoys me and go back in there to see what, if possible I can do.
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I've 'balanced' the clutch pack by suspending with a string up the middle. The discs will be parallel to the ground. Adjust positions till it doesn't lean one way or the other.
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I've 'balanced' the clutch pack by suspending with a string up the middle.
A local neighborhood Airhead buddy refers to that technique as his "Thong Method." [smiley=thumbsup.gif]
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I've 'balanced' the clutch pack by suspending with a string up the middle.
A local neighborhood Airhead buddy refers to that technique as his "Thong Method." [smiley=thumbsup.gif]