Motorcycle Questions? Ask a Mechanic.
Hi and thank you for your question.
I confirmed what you stated that for the bolts you are tightening, the manual does state 12Nm. If the fastener itself is at least 6mm in diameter and it good shape, it should take that no problem. However, depending on the grade of the bolt, it could be slightly high as well. 12Nm converts to about 9 Ft. Lbs. of torque and that is pushing the upper limit of a 6mm fastener. In an effort to help you sort this out, with no disrespect intended, I would suggest double checking your settings on your torque wrench to ensure they are indeed at the correct setting. If they are indeed correct, there is a possibility your torque wrench is out of calibration and causing you to over-torque the bolts and break them off. Another thought I can pass along is remember that click type torque wrenches are only accurate in the upper 80% of its range. That means if you had a 0 to 100 Ft lb torque wrench you should never use it to torque anything below 20 ft. lbs. If you would like to explore this further I would need to know what type of torque wrench (beam, click, digital) you are using and more detail about the bolt size. Bolt size means thread diameter, not hex size or socket/wrench you are using to turn it. The reason I question that is to enter the possibility that there is a misprint in the service manual providing incorrect information to you and creating this problem. Lastly, if you are using a click type torque wrench I would advise you to use extreme caution when torquing the bolts that you do not pull the tool past its break away point. Especially at lighter torque settings the breakaway can be very subtle.
If you have any more questions, feel free to ask.
If it was a defective torque wrench, I would suggest backing them all off and re-torquing all the bolts in a cris-cross pattern. I do not think you have damaged the cases. Typically the bolt will give up first, especially when it is a small diameter bolt.
I would worry about a long term seepage from the oil pan if you don't get all the bolts installed.
To take this a step farther, and heading towards maximum reliability, I would urge you to inspect each bolt that did not break to make sure it isn't stretched. A stretched bolt will have an hour glass shape in the threads and you will notice the gap between some of the threads is larger than others. If you see any bolts stretched, replace them. They will fail prematurely and will never take stock torque again.
Something is wrong. I can only think of 3 possibilities.You say you have eliminated one, the torque wrench. That leaves 2 options, either its a mis-print in the manual or the bolts had previously been over torqued and damaged.
You never mentioned what the range your torque wrench is and never said what thread diameter the bolts you are installing are.
I would inspect the bolts or just get all new ones because they could have (probably) got damaged from the first go around.
I would not leave 3 bolts out. I believe that the oil pan will start seeping over time. I trust Triumph designed the oil pan and fastening system to adequately seal.
I have never heard of pro point torque wrenches, but I suspect if they are being sold at an auto parts store they are designed to be used by weekend warriors. Auto parts stores don't typically sell professional grade tools because do it yourselfer's just won't pay the price. I also wonder how you tested it because calibration equipment is very expensive, much more expensive than the torque wrench itself.
Without some more specific information, there isn't much else I can do for you.
I have been thinking about this and it is bothering me that we can't seem to get to the bottom of it. I had another thought, are you by chance lubricating the bolts or is there residual oil getting on the threads? If the bolts are supposed to be installed for a dry torque and they get lubed, the reduction in friction will cause them to be over-torqued. Possible?