The New And Improved Unofficial R65 Forum V2
Technical Discussion => BMW Technical Q&A, Primarily R65 => Topic started by: georgesgiralt on October 17, 2017, 02:02:23 AM
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Hello !
I'm starting to gather the parts for a complete renew of my 200 000 km+ R65 motor.
So I began to buy new cylinders in order to buy the correct fitting pistons.
Funny BMW sent a "A" and a "B" jug ! So I've to order one piston "A" and one "B".
But inspecting my bike I saw that it was fitted at the factory with 2 size "A" jugs.
Is it somewhat important or ?
Thanks for your help.
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I can understand your concern and wonder why they couldn't be bothered to send you a matched pair but the nominal difference in bore size is only 0.01 mm or 0.0004" which I doubt makes any practical difference. I'd still want to check the piston weights and balance them.
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Thank you Barry !
I'll watch the pistons when I get them. And I bet I'll have to grind one of them a little.
I just don't know which part to grind ...
But wait and see...
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And I bet I'll have to grind one of them a little.
I just don't know which part to grind ...
But wait and see...
For trivial adjustments take metal from the bottom of the skirt, for more serious amounts the underside of the pin boss. With modern pressure cast pistons it is rare to see differences of more than a few thousandths of a gram. The last new ones I checked were accurate beyond my ability to measure the difference.
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Got the pistons today. Also from Mahle.
Came with the wrist pin, the two clips and all the rings.
I'm happy, they bear the same weight marks !
But they're not the exact same design as the original. The ridges above the top ring are not here anymore. And the wrist pin is free to move in the piston. No need to heat the piston to move them.
I'll weight them tomorrow to see how large the tolerance is at Mahle factory...
Boy, they look gorgeous !
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Boy, they look gorgeous !
What! No pictures?
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OK, I take some picts when I weight them...
Don't know if I will have time today. The wife has plans ...
Here they are ...
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Funny, the image is upside down in the Browser and correct in my computer ?
Another one
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Again
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As you can see, they're gorgeous but different from the original ones.
The weight is about 2 grams apart. Should I grind some metal from the heaviest ? (they're the same weight class by BMW standards) And if yes, where should I grind to get 2 grams off ?
Have a nice day !
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I tried running a pair of pistons that were 7 grams different
I could notice the vibration
So I pulled it apart and balanced them to.1 grams
To remove that much I had to remove a little from everywhere inside the piston except for the lower machined area of the piston skirt
(I assumed that is where they were they balanced them at the factory)
I took as much as I could from the wrist pin boss
After 3000 miles it has not come apart
After doing it I wondered if it would have been better to take some out of the inside of the wrist been also
My 2 original piston were only .2 grams apart
I would definitely balance them even with only 2 grams difference
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Hello Guys,
I need some help.
I've bought from BMW the gudgeon pin bushing for the connecting rod.
P/N 11 24 0 618 100 which are the correct P/N for my bike (they fit almost every engine BMW has produced and are less expensive for motorcycles than the car counterparts....)
When young I had been taught that the small end of a connecting rod has a bushing with a large interference fit. Once fitted, a hole is made for the oil passage and the bushing is machined to match the gudgeon pin properly. There is also another way which consist using a thin cylinder covered in non friction material. This cylinder is split and has a diameter bigger than the gudgeon pin. Once fitted to the rod, the inside diameter magically matches the gudgeon pin dia.
I've got a pair of the former. But they do not fit the pins. they are way too small so they won't properly adjust when inserted in the connecting rod....
I complained to the BMW dealer. He says this is the correct part because the correct P/N is printed on the satchel...
So I'm puzzled !
So could you please, if you can, post a picture of the P/N 11 24 0 618 100 if you have one ?
Many thanks in advance for your help.
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They are the correct part!
However they are not supplied "finished". You need to:-
1/. Buy the correct sized reamer and finish them yourself after pressing them into the rod (not recommended unless you have a lathe or mill as whilst bores can be hand reamed accurately, it takes time and practice, you will most likely not get it right the first time.
2/. Buy an adjustable reamer and "sneak up" on the correct size. This is actually a sensible suggestion as a fixed reamer is only good for one hole whereas an adjustable reamer can be used for many sized holes within a (admittedly narrow) range. Again though, unless you have used one before, or have a lathe or mill you can put it all in to maintain accuracy - I would not recommend it. The good thing is that adjustable reamers can usually be found very cheaply at 2nd hand tooling shops because they simply are not used much anymore (because customers baulk at the hourly charge for skilled hand work).
3/. Take the connecting rod, gudgeon pin and new bush to a competent machine shop and say "Sir, please press the bus into the rod and then ream the bush to fit this pin. Oh, and bye the way Sir, it is going into an air-cooled motorcycle" The last bit of allowing the machinist to select the running clearance is because I failed to find the BMW specified fitted clearance in the brief look I had just now.
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I tried running a pair of pistons that were 7 grams different
That looks like borderline criminality on the part of the manufacturer, I am astounded that two modern pistons could differ so much in weight - one or both should have been condemned at the manufacture.
I would not have tried running them and would have returned them for refund or replacement. Idly I just started the force calculation based on 7g weight at approximate maximum piston speed and I did not like the guesstimate answer that popped up. I am not surprised that your could feel a vibration, I suspect it would have been VERY noticeable.
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However they are not supplied "finished". You need to:-
I took option #4
The first motorcycle engine I was ever in was my R50/2 after I had dropped a valve. Being a "car guy" at the time I had no idea BMW didn't give me a part that I couldn't use. I called around ( pre internet) and found that this wasn't exactly a 283 Chevrolet and yes I had to ream the parts to fit.
I took my Brake hone for wheel cylinders and reamed it with that. Where in the Hell am I going to get a reamer the proper size on a Tuesday afternoon in 1974
Before the World had gotten so small with the Communications we have today, you fixed it any way you could ::)
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Tony,
The parts I've got can't be reamed. The metal is around one mm thick.... And if I open up the split in order to match the internal diameter to the external gudgeon pin, the split is about 4 mm wide.
Add to this the parts are made of steel with something slippery deposited onto it. So I bet if I ream them, gone is the treatment...
Next week I'll try to find an engineer apt to supply the correct bushing and adjust it to fit.
I agree with you that tools are easy to get second hand because a lot of people are retiring and nobody will take their job anymore.
I'll try to make a couple of pictures tomorrow.
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I've only swapped out pistons on two BMWs but I was able to press the wrist-pin (gudgeon pin to you guys on the wrong side of the pond - ;) ) with a finger, no press required. They were both on original untouched engines. There was a fair amount of "drag" when pushing them in and out.
Or, maybe I don't understand exactly what you are referring to.
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Tony,
The parts I've got can't be reamed. The metal is around one mm thick.... And if I open up the split in order to match the internal diameter to the external gudgeon pin, the split is about 4 mm wide.
It was a while ago but if what you have is actually a gudgeon pin bushing then BMW have changed them since i bought a pair in 2013 when I recommissioned the R65 - the ones I got were not split, required that I give the bore in the connecting rod the lightest touch with a hand reamer to clean up the bore. The interference fit still required that I shrink the bush in my local doctor's mole removal liquid nitrogen and heat the rod in an oven.
Once pressed into the rod I borrowed the correct sized reamer and finished the bore.
The part I got was definitely not finished, in fact I would be gravely suspicious of one that was supplied in finished condition as the interference fit of the bush into the little end would alter the diameter.
Maybe BMW have gotten very lazy if they are supplying split and finished bushes.
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I've only swapped out pistons on two BMWs but I was able to press the wrist-pin (gudgeon pin to you guys on the wrong side of the pond - ;) ) with a finger, no press required. They were both on original untouched engines. There was a fair amount of "drag" when pushing them in and out.
Or, maybe I don't understand exactly what you are referring to.
It usually requires nothing more than the application of very mild heat to get the pin to slip in and out of the piston easily. When I was young I used rags soaked in boiling water, in more modern times a hot air gun does the same job faster and with less mucking about.
The little end bush is what we are actually talking about, the idea being that this is a load bearing bush that must deal with rotation - the pin does not rotate in the piston, or at least it shouldn't really.
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OK, we're on the same "page." On the '82 R65LS and the '81 R100RT they just slid out with finger pressure. Guess I am just lucky!
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Tony,
The parts I've got can't be reamed.
The 4mm gap made me think. I think what you have is a little end bush for a G650, not an R65. I think this because the pin diamater is less and the rod is pressure cast so actually would have a reliable and repeatable bore size (still lousy engineering practice though - but typical of the way BMW has gone recently).
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The little end bush needs to be honed, any machine shop should still have a Sunnen hone, not a big job. I have adjustable reamers, but I wouldn't use them on a little end bush, they leave a 6 sided hole - that's ok for king pins, but not engine parts.
Fit them and check first. I did king pins in a Mitsubishi Canter a few years ago, got my reamers out ready, pressed the bushes in and then checked to see how much to ream out - and they were a perfect fit ! That's how much machining of parts has improved.
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The little end bush needs to be honed, any machine shop should still have a Sunnen hone, not a big job. I have adjustable reamers, but I wouldn't use them on a little end bush, they leave a 6 sided hole - that's ok for king pins, but not engine parts.
Speak for yourself. I am very confident that I can produce a very round hole with a reamer, but it took me a lot of failure to learn how.
OTOH I would not hone a yellow metal bush, it absorbs the media like a sponge.
But I do admit that honing technology has changed, I understand they you can even hone Nickasil bores now, something I thought would have been a recipe for disaster.
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Little end bushes have been honed forever without a problem. I bet they are honed rather than reamed at the factory. You can't ream a porous bronze bush, it blocks the pores, but you can hone them. I've always bottle brush honed nickasil and alloy bores, and are recommended for the job.
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Little end bushes have been honed forever without a problem. I bet they are honed rather than reamed at the factory.
You would be wrong. In a production line setting a hone requires more skill to use than a fixed sized reamer in a mill (or at least a pedestal drill with a big quill) as the workers are usually paid as little as possible the reamer wins.
You can't ream a porous bronze bush, it blocks the pores, but you can hone them.
That would be Phosphor-bronze and you definitely cannot hone them for the very reason you state - the hone lays the grain/pores over and blocks them - they are universally drilled and reamed.
I've always bottle brush honed nickasil and alloy bores, and are recommended for the job.
Actually if you read the product notes on Mahle's website (the people who made Galnickal/Nickasil affordable in a mass production setting) they specifically recommend against honing such bores unless you are using a special and very, very hard hone. The reason is in two parts and quite simple - Nickasil/Galnickal is bloody hard itself and much, much harder than old style hones, particularly readily available bottle brush type hones - those sorts of hones either wear very quickly and clog the Galnickal/Nickasil (the very reason why hot soapy water and scotchbrite is recommended for servicing and acid for severe alloy (from pistons) clogging).
The secondary reason traditional hones are specifically not recommended is that as the hone sacrifices itself whilst doing nothing helpful it creates local high temperature spots which can cause the Nickasil/Galnickal coating to de-bond from the alloy cylinder, with obvious fatal results to the cylinder.
If you have got away with using bottle-brush hones on carbide bores I can only suggest that the inevitable disaster is overdue.
As a brand Sunnen made/make excellent honing machines and I am sure that suitable hones are available for those machines.
BUT
The carbide coating on OEM cylinders tends to be very thin and it is quite unlikely that an otherwise unserviceable barrel will be recovered by trying to hone out imperfections or re-introducing hatching - this is not true of all OEM cylinders (Ducati being a good example) and is generally not true of cylinders processed by aftermarket carbide coaters - but it is universally true for OEM BMW cylinders.
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"accurate beyond my ability to measure the difference."
I like that phrase a lot and am going to have to find a way to work it into conversation.
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Hello !
The wrist pin problem will be settled, I hope, at engine dismantling.
I've measured (roughly with my caliper) the bushings and the wrist pin.
The wrist pin is at 22.0 mm dia. the bushing with it's opening closed is at 21.6 mm interior diameter. I expect it to be at around 21.5 or a little lower when fitted on the connecting rod.
The thickness of the bushing is 1.1 mm ... So I hope this will do.
My last concern is the interference. The set I have on the bike (original) has the wrist pin not moving in the piston skirt. And I suppose it is with some small play on the connecting rod... The new piston have the wrist pins free to move in the piston skirt. So I wonder if they should have the same play on the connecting rod or have some little interference ?
Of course all this is theoretical because I've not checked the connecting rods so I do not know if they will be reused or not.
I've started research on the heads. I've one with damaged exhaust threads. I've found a guy doing an aluminum threaded sleeve which it then solder in place; Very neat job. he is willing to repair my head. So far so good he can also replace the exhaust seats (I think they are questionable on my bike) and grind them with the proper angles. So I've started to spare money for the head job...
Slowly progressing but progressing :)
check this out. In French but with pictures...
http://www.flat-twin-bmw.com/t36417-une-reparation-du-filetage-d-echappement-sur-nos-vielles-culasses
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What was the outcome please? Were those split little end bushes really for an R65 or not?
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Well, for now, they sit with the other parts on the garage shelf.
I'm still saving for the valves and the valve job.
I plan to go to the local Guru and ask him, but it could be the correct part given how little metal I should have to remove to have the bushes fit.
Add to this that i won't do this myself and the engineer doing the job could make a bushing if needs be...
I'll report back in a few month when all the parts will be gathered and the job done.
Stay tuned ;-)