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Old 04-16-2014, 12:31 PM   #1
akabeton OP
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Location: British Columbia Canada
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Cylinder Head Nuts Torque Setting

I just wanted to double check this before I screw up.

Haynes - 18 - 23 Nm. ( 13.5 - 17 ft.lb )

Clymers - 35 - 39 Nm. ( 26 - 29 ft.lb )

Snowbum - 33.9 Nm max. ( 25 ft.lb max )


Bike is a 95 r100 GSPD with 35,000 miles.


Thanks
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Old 04-16-2014, 12:48 PM   #2
Big Bamboo
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I use 25 ft.lb which is less than recommended, but my fasteners are oily. Factory specs are for dry fasteners.
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Old 04-16-2014, 01:41 PM   #3
SOLO LOBO
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I'd say not to re-torque unless you have had the heads off and need to double check
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Old 04-16-2014, 03:13 PM   #4
chollo9
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I agree with both statements above. Studs pull out of the cases way too easily.
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Old 04-16-2014, 03:33 PM   #5
disston
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I use 25 ft/lbs. Three stages.

I do retorque my heads sometimes. 1975 R90/6. I think the early bikes are less prone to pull the threads tho.
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Old 04-16-2014, 04:59 PM   #6
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I have torqued literally 100's of heads to 26ftlb and have never had any troubles for it. I have torqued a lot to 28ftlbs and never had any trouble for it. The studs do not pull out of these cases way too easily unless they are over torqued. It's the same story with oil sump bolts and many others. Pay attention and do the job right with the right tool and there should be no problems. Threads that ARE easy to strip? Drive shaft fill and drain bolts, late model final drive oil height inspection bolts, and fork drain bolts. All for very little thread purchase but go figure.

Now I have read a couple of times that the early cases don't pull their cylinder stud threads as much as the later ones. I have been around these bikes a lot for a lot of years and I have never noticed that. But then again I hear all kinds of nonsensical stories about how the later engines are not as good as the earlier ones. My experience is just the opposite. The later cases are much better in many ways starting with much stronger main bearing carriers and it gets better from there. The real bad years IMO as far as trouble with the cases are /5 and early /6.

I don't re-torque heads as often as BMW recommends but they do need re-torquing. I would guess about half again of what BMW recommends is about right.

supershaft screwed with this post 04-16-2014 at 05:08 PM
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Old 04-16-2014, 05:21 PM   #7
chollo9
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Quote:
Originally Posted by supershaft View Post
The studs do not pull out of these cases way too easily unless they are over torqued.
Right. You're exactly right.
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Old 04-16-2014, 06:28 PM   #8
Stan_R80/7
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Both my Haynes manuals for BMW twins, 1970-1988 (published 1989) and 1970-1995 (published 1999) have a three stage torque specification for the cylinder head retaining nuts:

Up to 1980:
1st: 11 ft-lb
2nd: 26 ft-lb
3rd: 29.5 ft-lb
Final: 28-31 ft-lb

1981 on:
1st: 11 ft-lb
2nd: 18.5 ft-lb
3rd: 26 ft-lb
Final: 26-29 ft-lb

Personally, I use a maximum torque value of 25 ft-lb with a second stage torque value of 18 ft-lb which seems to work fine on my 1978 R80/7. I also check the calibration on my torque wrench before tightening the cylinder head nuts.
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Old 04-17-2014, 02:15 PM   #9
jackd
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Quote:
Originally Posted by akabeton View Post
I just wanted to double check this before I screw up.
Haynes - 18 - 23 Nm. ( 13.5 - 17 ft.lb )
Clymers - 35 - 39 Nm. ( 26 - 29 ft.lb )
Snowbum - 33.9 Nm max. ( 25 ft.lb max )
Bike is a 95 r100 GSPD with 35,000 miles.

Thanks
Are you doing some head work or just checking the torque prior to setting your rocker arm gaps? I just bring it up to around 20 ft/lbs if I'm doing the annual rocker arm check - no need to go the full torque.

On another note - I've been exchanging e-mails with our mutual friend. It would seem that we have many common acquaintences in our line of work - aviation is a small world. I'm sending him pics from my collection to remind him of his youth. He wants us all to get together for a ride over here on the Island - I'm hoping you can join us...
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Old 04-19-2014, 05:39 AM   #10
GrahamM
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I use 25ft-lbs on the r80 and r100. Three stage approach as well. All good, no leaks or troubles.
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Old 04-19-2014, 12:59 PM   #11
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Quote:
Originally Posted by solo lobo View Post
i'd say not to re-torque unless you have had the heads off and need to double check
+1
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Old 04-19-2014, 02:53 PM   #12
Stagehand
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torque specs here are there so they are not exceeded, rather than run up to. I should think all about equally snug anywhere between 20 and 25 will keep them from pulling anything. whats the cross section on 4 10mm bolts? Its a chunk of metal that would hold twenty bikes in shear, lol its not like the nut torque is gonna be what holds the cylinder on, even with the potato masher inside.


I haven't had any problems since that one time, and of course good judgment comes from experience which comes from bad judgement. Aint saying I haven't pooched it, but thats how I learn
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Old 04-19-2014, 06:55 PM   #13
ysrebob
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On a closely related note, is this kind of oily/sooty stain along the left cylinder base a sure sign of pulled cylinder studs?

Photo is from an '85 R80RT I bought last Tgiving and spent a lot of time restoring over the winter. Previous owner had botched all kinds of things to the point I'm amazed the bike was even driveable... loose suspension bolts, messed up wiring, butterfly plates backwards in the carbs and mismatched needles, etc etc etc... basically an unbelievable amount of ham-handed work had been done. Last thing he told me after I bought the bike was that he had just retorqued the cylinder studs. So it was with a vague feeling of dread that I noticed a fresh sooty leak along the top of the left cylinder base after I finally got it running again the other day and took it out for a test ride. Haven't had the heart to redo the stud torques yet... afraid of what I will find.
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Old 04-19-2014, 10:20 PM   #14
disston
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That is a small amount of seepage at the base of the cylinder. It is not a sign of anything except poor application of sealant or poor choice of sealant that was used. I get a bunch more seepage than that on my bike. Easy to clean. Will stay clean for awhile.

A retorque of the cylinder stud nuts would be advisable.
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Old 04-20-2014, 03:44 AM   #15
100RT
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I agree with Disston. In the past I used Hylomar and got seepage. Now use Yamabond and stays dry.
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