I swapped in new gaskets on both sides of the transfer case (for the first time in the bike's 33k mile history, apparently, going by how hard it was to get the old material off), and I'm having trouble getting the covers back on because the bolts keep shearing. I'm thinking maybe this is normal, due to stress on the metal from all the vibrations these tiny bolts have had to put up with.
The torque specs from the manual are:
Crankcase bolt (8 mm) 20 - 24 Nm (14.5 - 17.5 ft-lb)
They are shearing as low as 12.5 ft-lb.
I'm tempted to just order a complete set of new ones from bikebandit, but I want to get a second opinion before I just throw money at the problem.
Is it foot pounds or inch pounds? Just want to clarify.
If you can find bolts locally (dealer or even just a hardware store) you may be better off. And the age and vibration shouldn't have anything to do with them shearing.
Quote from: Big Rich on August 07, 2011, 02:17:44 PM
Is it foot pounds or inch pounds? Just want to clarify.
I've definitely made that mistake before.............not fun.
Very strange....Grade 8.8 M8 bolts torque up to a max of about 25Nm and should only start to yield at about 31Nm. I am thinking you are misreading the torque wrench or its hopelessly out of calibration. Other possibility is that the bolts are non OEM and of a lower grade than 8.8..........Grade 4.6 max out at 9.5Nm or 7lb/ft and grade 4.8 max out at 13Nm or 9.5lb/ft........which might explain things.
Has it got one of those cheapo after market bolt kits fitted to it?
Aftermarket bolts seem like the most obvious answer, outside of the torque wrench being out of calibration. I've used it to put the entire engine together twice now, so I'm hoping it's correct and it's just bad bolts. :icon_confused:
They made it to 9.5 safely enough. I can't tell if it's got aftermarket bolts just by looking at them, since I don't have anything to compare them to.
Quote from: sledge on August 07, 2011, 03:01:04 PM
Very strange....Grade 8.8 M8 bolts torque up to a max of about 25Nm and should only start to yield at about 31Nm. I am thinking you are misreading the torque wrench or its hopelessly out of calibration. Other possibility is that the bolts are non OEM and of a lower grade than 8.8..........Grade 4.6 max out at 9.5Nm or 7lb/ft and grade 4.8 max out at 13Nm or 9.5lb/ft........which might explain things.
Has it got one of those cheapo after market bolt kits fitted to it?
It's definitely foot pounds, and I was checking the ft-lbs *and* the NM settings on the torque wrench to make sure they were under the actual spec.
Quote from: Big Rich on August 07, 2011, 02:17:44 PM
Is it foot pounds or inch pounds? Just want to clarify.
If you can find bolts locally (dealer or even just a hardware store) you may be better off. And the age and vibration shouldn't have anything to do with them shearing.
correction: I ordered 1 replacement bolt already when I ordered the gaskets in the first place, because I suspected one might sheer off and it was only a buck to have one on hand. It looks exactly like the rest, which makes me believe they are all OEM. I'm terrified of torquing them down, so right now they've just been hand tightened. I might leave it like that.
Quote from: sledge on August 07, 2011, 03:01:04 PM
Very strange....Grade 8.8 M8 bolts torque up to a max of about 25Nm and should only start to yield at about 31Nm. I am thinking you are misreading the torque wrench or its hopelessly out of calibration. Other possibility is that the bolts are non OEM and of a lower grade than 8.8..........Grade 4.6 max out at 9.5Nm or 7lb/ft and grade 4.8 max out at 13Nm or 9.5lb/ft........which might explain things.
Has it got one of those cheapo after market bolt kits fitted to it?
I've had the exact same problem with those crankcase cover bolts. Perhaps the torque spec listed on the wiki is wrong? Either way, I snapped about 3 of them and had to order replacements. In the end I tightened them by hand to that they were snug but made extra sure to not over tighten them. It's held up so far with no leaking oil, so that's good enough for me. Either the torque spec is wrong or those bolts are made of cheese.
I always put a small drop of blue loctite on those bolts to insure that they don't back out.