Topic: cb750 cylinder stud woes - buyer beware.

[PeWe]

My new set I bought locally here at the old tuner looked exactly the same as the set I bought on eBay contained one that snapped.

I'm worried anyway. I hope they will not snap when I torqued less the other time. Cometic fiber head gasket might be softer for the studs as well.

I'll replace them next time the engine is out. I saw that CycleX has HD studs manufactured by Kibblewhite.

[PeWe]

Important to not believe in excessive torque. Kibblewhite specifies max 22 ft lbs.
"Tighten the head nuts down evenly to achieve 18 lb ft minimum to 22 lb ft maximum"
http://valvetrain.kpmivalvetrain.com/Asset/999-101355.pdf

[KrautKoffin]

You should just delete this thread.

[Jerry Rxman Griffin aka MuthaF'er]

Even if they weren't ours, but the guy thought it was, we don't care, we send him a replacement anyway. We have had people over tighten ours and pop the top off in the past, so we just take care of the guy.

Jay

Not to say a stud broke or didn't break or whose it was BUT.... I'm a Jay backer (but staying out of this 'situation'). I can attest to the effort he goes to in order to make things right. We worked through a difficult, expensive and time consuming situation and he took great care of me! Thanks again Jay. These old Hondas are what he got started with and I'd BET he cares more for our bikes than the Busas even though his bread is buttered by Suzuki stuff. AND it's my understanding all the CB750 machining is done by no one else besides Jay.

[PeWe]

You should just delete this thread.

Why delete?
Information like this is very important on a forum where things are up for discussion.

Fact is that there are several threads about snapped studs, especially since 2009/2010. Your story ended up in a major engine damage nobody wants.  It can be very dangerous if the engine suddenly lock-up. I have HD primary chains that will withstand forces longer before release getting a worse situation with a nut locking up.

It can be seen that IF one stud snap, replace them all when it might be a bad batch or just something else....

I want to replace all mine since I read your story. I have snapped one HD stud when assembled the engine April 2013, replaced the only one that snapped. I cannot continue with the 15 other HD studs that might be bad and get broken engine if lucky when locking up.

I'll take the engine out when I need to double check o-rings under the cam towers. I have never forgot them before but I'm not sure this time.

The winter is here and I have time. I have to trust the engine when I have spent rather much on the bike the last 2 years.
I'll try the Kibblewhite next time, that's why I found the instruction and its max torque.

[PeWe]

Check torque wrench!
I snapped one HD stud as I wrote earlier. Replaced only the snapped one despite I bought a complete set. I had that in my mind since then which I have to cure.
I bought a new complete set of HD studs AND a new torque wrench when it is better than borrow from the mechanical lab at my job.

My idea was to replace stud by stud without taking head off. First step was to find actual torque with my new torque wrench. I had to tighten about 36Nm to make the nuts to move!! tested on several head nuts. I know that I torqued less 2:nd time after stud snapped, about 19- 20 ft lbs (25.7-27nm). Now almost 1 year later it should not need more to tighten it further. The torque wrench I used when stud snapped must have been way off! 36 instead of 26Nm is 10/26 over torque +38% !!

This means when I torqued ~21 ft lbs was in reality >28 ft lbs!  Instruction with Kibblewhite HD studs states 22ft lbs as max. I think APE has same limit.

I trust my new torque wrench. HAZET 5120-2CT  Made in Germany, calibrated Oct 2013 and has almost spot on at 36Nm.
Invest in tools you can trust, it can cost a lot to repair.

[Jerry Rxman Griffin aka MuthaF'er]

Very good point indeed. I have a Harbor Freight (cheap) clicker and an older Sears Craftsman pointer that I can compare. They are close. My cheap clicker is good when comparing and it's very handy as I don't have to watch a dial which makes me feel the clicker is actually the better of the 2.