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Discussion Starter #1
Hi All,

I was putting the bottom and upper end crankcase back together and, unfortunately, I over torqued all of the 6mm (i.e., 8mm bolt head) by using a torque wrench improperly ultimately breaking one of the longer bolts. I was able to get the broken shaft out pretty easily, and I was very thankful for that.

My questions are do I need to replace those over torqued bolts? Should I be worried about any damage to the threads in the crankcase? Can I get replacement bolts from the hardware store or should I get used ones that came off another cb350 on eBay?

Thanks in advance.
 

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I wouldn't use a torque wrench on the long 6mm bolts you will twist them off. I just use a 1/4 inch ratchet and go by feel, no need to go too tight with them.
 

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1/4 Inch Torque wrench is better, 0-200 inch lbs. Devices like this are more accurate in the middle of their range.

Except for the axle bolts, and rotor nut, a 1/4 inch set is more than enough for the bolts on a motorcycle. 3/8 is sufficient for a car.. 1/2 is Medium truck.....

All those sizes are for normal repairs. For the odd BIG bolt or nit (Spring U-Bolts for instance), then a larger set is necessary.

Harbor Freigh has one for $22 http://www.harborfreight.com/1-4-quarter-inch-drive-click-type-torque-wrench-2696.html
 

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If you do use a torque wrench, use a 3/8 drive one set from 72-84 in lbs.
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+1 ;) or 1/4" drive I've also gone by 'feel' on those. I think some good,fresh,stock,O.E. Honda(only because they are flange bolts which helps them stay tight once they're torqued down) used crankcase bolts that haven't been stretched would be my way.
When you tighten them,just try to match the torque evenly on all the 6mm bolts in 'a pattern' that makes sense to you...
I would use a 'cross pattern' sequence, such as should be done on the top end/cyl.head. Stay away from tightening them 'all on one side',and then 'all on the other side'... Go w/ that 'cross pattern' and 'about a half turn on each bolt at a time to very slowly and progressively 'draw' both crankcase halves together until they become as One. ;)
Make sure you check your 'knock pin' alignment and the holes they go into,seals,bearings w/ clips,etc. to be sure everything sits flush and that the two crankcase halves get drawn down smoothly and equally w/ no resistance.
I hope you enjoy rebuilding this one.
 

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Remember most torque numbers are for clean dry bolts/nuts, if oily, wet or with loctite torque should be reduced 10% to 15%.

There is probably a torque formula for long bolts to account for twist due to length but I don't know maybe someone will post info.

I know some hardware is not so good, I rebuilt my Suzuki GS500F and a few of the head studs felt weak getting close to recomended torque, I stopped there to avoid snapping them off. I wasn't going to take it back apart, you can make a career out of some if your not carefull.
 

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Hi,

These bolts are not very expensive, so when over torqued, replace without hesitation. Torque down dry, or with grease, and extract 15 to 20% of the specified torque. Use a torque wrench within the range of the specified torque, preferably were the specified torque is between 50 to 90 % of the maximum torque of the wrench. I have three torque wrenches, every wrench has it's unique range and at least 20 % overlap in range for the next wrench.

It is possible to go by feel, but you should check the error on bolts between go by feel and a torque wrench, just to see your feeling is within 10 % of the specified torque. I use a torque wrench, knowing (tested) that my feel is more then 10% off the specified torque.

I have disassembled many engines, and I have seen many destroyed threads, so be careful with go by feel.....

Almost every oil leaking engine where the oil is not leaking via an oil seal is in most cases related to scratched seal eras and torque issue's.

Jensen
 

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I would use high tensile grade 8~9 bolts, the 'hardware store may only be grade 4 or 5?
Without completely stripping bottom end off you can't really check threads but if the bolt snapped and you got the broken piece out easy I wouldn't worry about it. 6mm bolts should have a 10mm flanged head, if you have 8mm flanged heads they are from a much newer bike, probably late 80's. They only need around 7~9ft/lbs which isn't an accurate setting so you would have to get an inch /pound torque wrench, I usually use around 90 inch pounds (when I can be bothered, slight 'tweak' after 'finger tight is close enough) I do torque the 8mm bolts with 12mm flanged heads though
 

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Discussion Starter #11
Thanks everyone for your input. Crazypj--Thanks for the grade info, super helpful. I was wrong originally, my 6mm bolts do have 10mm flanged heads, I don't know why I said 8mm, I don't even have an 8mm socket.

I got a 1/4" in.lbs torque wrench coming in the mail, can't wait to get the engine back together.
 

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Discussion Starter #12
Follow-up questions...

So, I couldn't find the 6mm x 150mm bolts at my local hardware store along with the other non-traditional lengths (e.g., 56mm, 45mm, 115mm), and bolts depot don't seem to carry any in that length. I'm considering buying a whole kit off of ebay but there are many different kinds and I'm wondering if there's a difference in the type of head. I see socket bolts (allen), flanged heads, and hex heads. Is there a difference in function that I should be aware of or is a bolt a bolt? Or does anyone have any suggestions about other places to get the bolt kit?
 

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Honda ?, just order the bolts you need.
 

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Discussion Starter #14
That's a good idea, should've been my first step after the hardware store.

Okay, I just checked out my local dealer's site and they have what I need except for the 6mm x 56mm bolts, they are discontinued and they don't offer them. Oh, well, I'll just get a 6mm x 60mm and hacksaw it down.
 

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If you put a nut on the 60 before you cut, it will make the threading easier.
 

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I doubt that 4mm will make a difference. The threaded holes should be deep enough to accommodate a 4mm longer bolt.
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Hi,

I have other experiences with some bolts on a CB450, superseded, different length bolts are in some cases not correct and hit the bottom before they hit the crankcase cover. Always check, but I admit, in 95% of the cases when Honda has a superseded bolt it will fit.

Jensen
 

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I ordered three new bolts for the alternator cover on my CL350, just because the old ones looked kind of nasty. Honda has superceded the original ones and the difference is not to my liking. The old ones had a short thread length, with a smooth, unthreaded shank above the threads where they pass through the O-ring seals. The new bolts are threaded all the way to the head of the bolt. This means that every time the bolts are removed, the O-rings are disturbed and want to come out with the bolts. It won't affect the seal, which is accomplished by the O-ring being slightly compressed between the conical bolt head and the counterbore in the cover, but still . . .

Ray
 

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Yes, same thing with the CB450 alternator cover screws. I'm always glad when disassembled an engine end the original are in good enough shape to send them to the plater. I did disassembled 6 CB450 engine's last month, saved almost every fastener, so these can be re-plated.
 

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I know this is an old thread —*but do you have input on what size bolts each of the CB450 crank case has?
 
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