Crack Conrod Torque - K-Bikes.com - Excellence in Motion
 
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Old Jun 17th, 2008, 2:50 pm Thread Starter
 
Join Date: Jun 2008
Posts: 4
Crack Conrod Torque

I've just purchased a '98 K1200RS. There was a problem with one of the connecting rods.
It subsequently smoked the crankshaft. A new crank and connecting rod were ordered. I weighed the rod (split conrod) with the studs, no nuts and no bearing inserts to order a new rod within weight specifications (4g).
The new conrod arrived. It looks like the part has been updated. It is a crack conrod with threaded shoulders and bolts with 12-point "star caps." The rod is within specs but when the original rods are weighed with the studs and nuts they are about an ounce too heavy.
So I ordered 3 more rods to make sure everything is within the 4 gram limit.

Since these are a different style rod:
What is the torque specification and/or angle? Is it the same stated in Clymers or the shop manual?
Can the conrod bolts be re-used? The bolts that came with the new rod appeared to be already torque'd.
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Old Jun 17th, 2008, 5:38 pm
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Quote:
Originally Posted by BlackGSD
I've just purchased a '98 K1200RS. There was a problem with one of the connecting rods.
It subsequently smoked the crankshaft. A new crank and connecting rod were ordered. I weighed the rod (split conrod) with the studs, no nuts and no bearing inserts to order a new rod within weight specifications (4g).
The new conrod arrived. It looks like the part has been updated. It is a crack conrod with threaded shoulders and bolts with 12-point "star caps." The rod is within specs but when the original rods are weighed with the studs and nuts they are about an ounce too heavy.
So I ordered 3 more rods to make sure everything is within the 4 gram limit.

Since these are a different style rod:
What is the torque specification and/or angle? Is it the same stated in Clymers or the shop manual?
Can the conrod bolts be re-used? The bolts that came with the new rod appeared to be already torque'd.

Look like you are going to have to do some part number research on www.webparts.com and find out what was shipped to you.

It looks to me on the two pdf's I sent that there is a difference between the '98-'00 and '02-'04 conrod along with different torque values (30Nm. vs 20Nm.).
The later('02-'04) conrod also states to use "new bolts"! Although I doubt the new conrod bolts were torqued to 20Nm. +80 angle. (Torque is for dry bolts before instillation.)
If you need more spec. information let us know. I have both '98-'00 and '02-'04 manuals.

I am a little confused on your term "split conrod" as in the rod cap being split at 90 to the centerline(small bore to big bore) of the connecting rod? And the term "crack conrod" as in the rod cap split at 45 to the centerline(small bore to big bore) of the connecting rod? Are my assumptions correct?? Or are we just talking about different terminology for rods w/studs and rods w/ bolts?

I looked through the oil filler hole on my '04 K1200RS and the rod cap looks like a 12pt. bolt on a standard "split" (my term) rod cap. No studs!

PS. Just added a pdf for '02-'04 connecting rod weight codes/ piston weight codes. This page is missing in my '98-'00 manual.
Attached Files
File Type: pdf '98-'00 K1200RS CONROD TORQUE.pdf (104.0 KB, 20 views)
File Type: pdf '02-'04 BMW K1200RS conrod specs.pdf (207.8 KB, 19 views)
File Type: pdf '02-'04 BMW K1200 connecting rod: piston weight codes.pdf (37.9 KB, 14 views)

Bruce C
'04 K1200RS Capri Blue(totaled)
2008 Triumph Sprint ST

Last edited by brucecha; Jun 17th, 2008 at 6:44 pm.
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Old Jun 18th, 2008, 1:11 am Thread Starter
 
Join Date: Jun 2008
Posts: 4
There are two conrod types at webparts.com for the '98 K1200RS: connecting rod diagram # 11_1771 and split conrod Diagram # 11_2790. The weights of the original conrods fell witin 413-416g. The connecting rod part number on diagram 11_1771 is 11-24-1-465-003 and the part number on split conrod diagram 1_2790 is also 11-24-1-465-003. Hence the delimma.

The split conrod must be the replacement for the older rods with studs and nuts. The problem is the weight measurement. The older rods are weighed without nuts, the new rods are nutless. So when nuts are added the weight variance is too great. The only solution is to buy three more to make a complete set.

The split (crack) conrods are nice in that the come as one piece with a line scored where the cap mates with the rod. The bolts are loosend about 1/4 inch then you hit them with a brass hammer to break/crack the rod at the score line. It is very nice because the caps cannot be mixed-up accidently and cannot be installed upside-down due to the nature of the crack.

All the documentation I've read only references connecting rods with studs and nuts, not the twelve point bolts. Since the split rods are newer (on brucecha's '04) do I use the new torque angle
20m then 80 degrees or the old 30nm then 80?
I suspect the newer 20 then 80 since the split rods have a tighter starting fit due the the nature of the crack instead of two flat surfaces requiring a greater initial torque.
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Old Jun 19th, 2008, 5:22 pm Thread Starter
 
Join Date: Jun 2008
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I just checked the crankshaft part numbers for the '98 K1200RS and the later K12's. They are the same. It looks like I should use the torque settings for the later model 20Nm. +80 instead of 30Nm +80.
Thanks for the attachments.
BTW Do you have pdf's for airheads? This is my first K. In 1990 I purchase a '78 R100RS. I got hit..it was totaled in '92. There weren't any R100RS's available locally so I bought a '76 R90/6 then a few years ago I managed to get my hands on a '83 R100RS.
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Old Jun 19th, 2008, 7:56 pm
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I have none. Try www.airheads.org and www.bmwsporttouring.com and go from there.

Bruce C
'04 K1200RS Capri Blue(totaled)
2008 Triumph Sprint ST
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