Topic: WHy me!!!!

[elquenada]

i just finsihed torquing down my split case.  everything was perfect.  and then...

one of my case bolts snapped while tightening it down.  great now I'll have to pull the whole thing apart agAin! 

[Terry in Australia]

500/550 mate? Was it the really long 8mm case bolt nearest your drive sprocket? I had a similar issue with Al Harpers' 550, when I took the bilt out it was actually busted and hanging by a thread, came out in one piece, but the threaded portion literally fell off, looked really corroded? Cheers, Terry.

[elquenada]

nope it was a small one in the front of the engine.  i tightend down too far and it just fell fight off.  at least I used anti seize on it; i hope it comes out easy. 
i already tore the engine back apart. words cant express how angry i am right now.

[BobbyR]

nope it was a small one in the front of the engine.  i tightend down too far and it just fell fight off.  at least I used anti seize on it; i hope it comes out easy. 
i already tore the engine back apart. words cant express how angry i am right now.

If you used the dry torque value when using anti sieze you need to reduce the torque value about 20%. People often snap bolts that way.

[elquenada]

nope it was a small one in the front of the engine.  i tightend down too far and it just fell fight off.  at least I used anti seize on it; i hope it comes out easy. 
i already tore the engine back apart. words cant express how angry i am right now.

If you used the dry torque value when using anti sieze you need to reduce the torque value about 20%. People often snap bolts that way.

actually I read your post this morning about dry vs wet torque value and so I reduced the amount by 20%.   Luckily the bolt snapped with just enough meat left on it and I was able to slowly spin it out.

Ill have to clean everything up and give it another go tomorrow.

[MCRider]

nope it was a small one in the front of the engine.  i tightend down too far and it just fell fight off.  at least I used anti seize on it; i hope it comes out easy. 
i already tore the engine back apart. words cant express how angry i am right now.

If you used the dry torque value when using anti sieze you need to reduce the torque value about 20%. People often snap bolts that way.

actually I read your post this morning about dry vs wet torque value and so I reduced the amount by 20%.   Luckily the bolt snapped with just enough meat left on it and I was able to slowly spin it out.

Ill have to clean everything up and give it another go tomorrow.

Did it bottom out in the hole?  Did the hole have gumby in it, glass beads, or debris?

[elquenada]

not really sure what happened.  i guess it could have been debris.  let me ask a dumb question...

do all of the case bolts get torqued to the same spec as the ones surrounding the crank?  I was tightening down to 14lbs and the bolt just popped off.


 

[MCRider]

not really sure what happened.  i guess it could have been debris.  let me ask a dumb question...

do all of the case bolts get torqued to the same spec as the ones surrounding the crank?  I was tightening down to 14lbs and the bolt just popped off.

Heck no!        The ones around the crank (at least on the 750) are 8mm hardened. (12mm head) The others are 6 mm (10mm head) of a softer material. Not sure how much, but a lot less than the carnk mains. Probably 6 to 8 ftlbs.

[elquenada]

yeah well that was a hard lesson learned.

[Terry in Australia]

Oh well, look on the bright side mate, you've answered your "Why Me?" question at least, ha ha! 

[elquenada]

lol. i was thinking the same thing.

[dave500]

i dont torque the small ones,just tighten them with a fist rachet.,i always chase all threads aswell while its apart and wire wheel every bolt.,then assemble them dry.

[Yoshi823]

The post about reducing the torque for bolts with copaslip on them reminded me about when I was doing the engine on my 750F2. I used some moly assembly lube, but I found that the bolt seemed loose in the hole once tightened to the specified torque setting. So I cleaned the assembly lube from the bolt & the hole and just used engine oil instead.

I seem to remember that the figure on the top of the bolt signifies the torque ability of the bolt. Without going out to the shed to get the manual out (it's -3c out there at the moment), i'm pretty sure that the Clymer manual has a table with the figures for the differant bolts and there torque ability.

[elquenada]

well engine is now back together.  it was a pain but I really dodged a bullet here cause the broken bit came out with little fuss. 

as fas as what ive learned...the manual needs to be read with more care.  In the back of the clymer manual there is a list of torque specs that says "upper and lower crankcases 15-19 ft lbs"  and then another that says "crankcase and covers 5-8 ft lbs".

The honda manual listed different torque specs for different bolt sizes but I could swear the smaller bolts were supposed to be at 14 ft lbs and since im a very green "mechanic"  I thought 14 sounded pretty low so I thought nothing of it.  wrong!

anyway it all shook out in the end.  thanks for the input as usual.
 

[bucky katt]

you might want to get the factory manual as a download. the manual for the cb750 is here http://www.sohc4.net/index.php?q=node/133 i have a factory manual and it's an earlier one. the translation sometimes makes for strange syntax in the explanation of procedures sometimes but theyre still very clearly explained. my factory manual is the bible in my shop.