Torque for the engine slider MT07

[Shyan]

Hi, I just wonder the factory specification torque is only applicable for using factory bolt? (Font Left Right bolt using 75nm or 55ftlbs)For after market slider it will having lower torque setting? I have customize slider for my bike and using 12.9 bolt (Have check the bolt spec in my local hardware shop) but when i try to torque to specific torque it start slippage and I stop..i did found some left over metal in the bolt itself but i clean it up and do not dare to keep tighten the bolt...

Edited April 8, 2022 by Shyan

[M. Hausknecht]

Oopsie! The bolt in question threads into aluminum (the cylinder head). From your description, it appears you've at least started to strip the threads in the head. The frame slider should have come with a bolt longer than the original bolt, to assure sufficient threads are engaged in the head. The strength of the bolt in this situation isn't the weak link; it is the threads in the head.

I believe it is imperative to achieve sufficient torque on those bolts, in order to stiffen the wimpy frame and to assure the motor doesn't move around in the frame. So, I think you're looking at needing to install a thread insert in the head so you can achieve the needed torque. 

[Shyan]

Just now, M. Hausknecht said:

Oopsie! The bolt in question threads into aluminum (the cylinder head). From your description, it appears you've at least started to strip the threads in the head. The frame slider should have come with a bolt longer than the original bolt, to assure sufficient threads are engaged in the head. The strength of the bolt in this situation isn't the weak link; it is the threads in the head.

I believe it is imperative to achieve sufficient torque on those bolts, in order to stiffen the wimpy frame and to assure the motor doesn't move around in the frame. So, I think you're looking at needing to install a thread insert in the head so you can achieve the needed torque. 

Ya i guess so... the bolt is longer than stock bolt...but during the torque down, I feel some slip then immediately stops it. When I reopen it, only the tips have slightly metal shred... maybe slip around 8 degree...(Simply wild guess ) Now i just torque it down to tight but not slip (Around 30ftlbs using torque wrench.) 

My question is do the factory torque spec still necessary or just as references  since I have "upgrade" the bolt from stock into "stronger" bolt..(What I research is 12.9 is the carbon mixture on this bolt..so it is definitely stronger than the stock bolt...Try to drop two bolts into ground and after market 1 are way more solid sound..)

Edited April 8, 2022 by Shyan

[M. Hausknecht]

The torque on a bolt creates the clamping force needed to secure the clamped parts; in this case, clamping the motor to the frame. A stronger bolt doesn't create more clamping force than a weaker bolt unless you apply more torque to the fastener than you would to the weaker bolt. In any event, as you've discovered accidentally, the weak threads in the aluminum cylinder head are the limiting factor, not the strength of the bolt. The stronger bolt in this application is intended to assure that if you drop the bike on the frame slider, the stronger bolt is less likely to bend or break.

With less torque on these fasteners than intended by Yamaha, you run the risk of the motor shifting in the frame. The bolt is also more likely to loosen up on its own, causing even more movement between parts that are intended to be joined rigidly. Sorry to be the bearer of bad news.

[Shyan]

Just now, M. Hausknecht said:

The torque on a bolt creates the clamping force needed to secure the clamped parts; in this case, clamping the motor to the frame. A stronger bolt doesn't create more clamping force than a weaker bolt unless you apply more torque to the fastener than you would to the weaker bolt. In any event, as you've discovered accidentally, the weak threads in the aluminum cylinder head are the limiting factor, not the strength of the bolt. The stronger bolt in this application is intended to assure that if you drop the bike on the frame slider, the stronger bolt is less likely to bend or break.

With less torque on these fasteners than intended by Yamaha, you run the risk of the motor shifting in the frame. The bolt is also more likely to loosen up on its own, causing even more movement between parts that are intended to be joined rigidly. Sorry to be the bearer of bad news.

I just send to my mechanic friend to let them recheck everything  So far they have recheck the bolt and everything they say no issue found... I think story ends here then  They know better on the machine itself. I read thru some brand like R&G Frame slider, they only recommended 40nm on their setting not the factory specification which is 75nm. In short can I understand as once use any bolt apart factory bolt, the torque setting is different?

Edited April 10, 2022 by Shyan

[Mrozzie5184]

Good to know the torque spec I plan on doing this next weekend, I assume blue locktite is recommended

[Shyan]

Just now, Mrozzie5184 said:

Good to know the torque spec I plan on doing this next weekend, I assume blue locktite is recommended

I think you may follow the recommended torque spec of your slider if you have it... and stop immediately if you feel slip while torque down your bolt...