Stripped front motor mount bolt

I went to check the torque on various bolts after a mechanic had rebuilt the motor on my WR400 and put it back in. According to my manual the front motor mount bolt is to be torqued to 50 ft lbs. I put the socket on the nut and an open end wrench on the bolt head and tried to tighten it. It turned fairly easily. I turned it about 1/2 turn, then there was a sharp snap noise and the nut basically fell off the end of the bolt. All the threads were pulled out of the nut.

I was hoping to get to the desert today, so this morning I went looking for a new bolt and nut. I ordered one from the dealer, and then found a 3/8 x 6-1/2 bolt at a surplus hardware store. It was a Grade 5. It is slightly smaller in diameter than the stock bolt. I put it in and tried to torque it to 50 ft lbs and sheared the bolt in half. So no riding today.

Can someone confirm for me that 50 ft lbs is the correct torque on the front and bottom motor mount bolts?

Anyone else run into this particular problem?

Does it matter whether I have the torque wrench on the nut vs. the torque wrench on the bolt head?

Thanks in advance for any comments.

The torque wrench goes on the nut, not the bolt.

I will comfirm that. I will post a torque chart when I get back to work. This seems to be a popular question. I think I will take a few bolts and nuts to work and check with our Alloy Analizer to find out what type of materal they are using, as this will also effect the torque numbers.


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