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Online Aggie95

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Re: Missing Engine Mounting Bolt
« Reply #40 on: September 11, 2019, 04:48:48 PM »
Here's a pic of the locations from the service manual...




1971-1973: '67 CL77 (305 Scrambler), Sold, because my wife said to...
2018: '14 CB500X, The dream bike of my youth!  Thanks, Son

Online Aggie95

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Re: Missing Engine Mounting Bolt
« Reply #41 on: Yesterday at 04:52:57 PM »
*Originally Posted by Aggie95 [+]
Y'all can call me a "fair weather rider", but it's hot in Texas right now, and I'm not riding much; waiting for cooler weather!!  It'll be a few months before I ride enough miles to test this "fix", but I think it will.

Update: Late September 2019
My son and I trailered our bikes to eastern Colorado for a jumping off point for a ~2600 mile circle across southern Colorado, southeastern Utah, a little of northern Arizona, then through central Utah, across northern Colorado to far eastern Colorado ending up where we started.  The ride started on a Saturday morning and ended just after dark the following Friday.  We rode the high plains, several mountain passes, high dessert and a lot of absolutely gorgeous scenery!

But, the point of this post is to announce that I think I have solved the vibration problem that keeps cropping up with my GIVI engine bars. 

In a previous post, I theorized that the bolts that came with the GIVI bars are not long enough to provide sufficient thread engagement in the aluminum engine block.  My theory was the aluminum threads were yielding with the energy induced into the bars by resonance created by the engine exciting a natural frequency of the bars.  That's why we have to keep re-torquing the bolts.  I reported that I replaced the 40 mm bolts with 45 mm bolts and torqued them to the torque indicated in the Honda service manual.  In the past, when I re-torqued the bolts, the vibration I felt at 4600-5000 rpm would go completely away.  But, it would return in about 2000 miles. 

I can now report that I believe the longer bolts solved the problem.  After 2600 miles, I feel no vibrations.  In the past, the vibration would be getting quite obvious by now.  Of course this doesn't prove that the problem is solved; the vibration may return at some longer interval.  But, it is a significant improvement over the original bolts!

1971-1973: '67 CL77 (305 Scrambler), Sold, because my wife said to...
2018: '14 CB500X, The dream bike of my youth!  Thanks, Son

Offline SilverCycle

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Re: Missing Engine Mounting Bolt
« Reply #42 on: Yesterday at 07:08:32 PM »
If the bolts are working undone, is it viable to use threadlock?

Online Aggie95

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Re: Missing Engine Mounting Bolt
« Reply #43 on: Yesterday at 08:15:40 PM »
*Originally Posted by SilverCycle [+]
If the bolts are working undone, is it viable to use threadlock?
I don't think so, at least not as much.  I think the problem lies in the low yield strength of aluminum.  It's not that the bolts are loosening, but that the aluminum threads are yielding (stretching) because the combined stress on the threads induced by the torque of the bolts and the additional stress from the vibration induced resonance is beyond the strength of the aluminum.  Adding a thread locker will help this, but only by a small amount.  Much more effective is adding thread engagement.  The additional 5 mm of thread engagement provided by the 5 mm longer bolts almost doubles the original thread engagement, essentially doubling the strength of the connection.
 
I often saw this characteristic before I became an engineer when I was a mechanic specializing in high pressure hydraulics.  I encountered many aluminum bodied pumps and I noted that the bolts that hold the bodies together always had about 2 1/2 to 3 times the thread engagement of similar cast iron/cast steel bodied pumps.  As an engineer the reason why becomes obvious; aluminum has about half the strength of steel (but one third the weight).

1971-1973: '67 CL77 (305 Scrambler), Sold, because my wife said to...
2018: '14 CB500X, The dream bike of my youth!  Thanks, Son

Offline timur

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Re: Missing Engine Mounting Bolt
« Reply #44 on: Yesterday at 09:24:07 PM »
My thoughts about Givi bars. I worked about 10 years as stress and F&DT engineer and in my opinion Givi bars has veeery poor design. They forces engine mounting bolt to withstand bending loads - something they never was intended to deal with. It's not a culprit of Honda but Givi designers.

OEM Honda crash bars are year lights ahead - they use silentblocks to isolate the bars from engine vibration and doesn't overloads engine mounting points. For sure they thoroughly asessed vibration issues via PSD analysis with some FEM tool (Abaqus, MSC.Random, etc.) - something that GIVI couldn't even dream of. Mostly because Honda has more information and resources to perform this task - an advantage of being a manufacturer.

Regards,

Timur

Online Aggie95

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Re: Missing Engine Mounting Bolt
« Reply #45 on: Yesterday at 09:39:57 PM »
I only have experience with GIVI bars.  But, all the crash bars are like huge tuning forks attached to our bikes.  Every brand will have its own natural frequencies that may or may not match up with engine/transmission exciting frequencies.  But, it sounds like Honda has performed the frequency analysis required to identify and eliminate the problematic frequencies.  I would expect as much from Honda.  As you mentioned, they have the deep pockets for such engineering, and the Japanese tend to be very quality conscious; that's why we like their products!

Wasn't always so; when I was a kid, we used to cringe when we got a toy marked "Made in Japan"!! Now most of my toys and tools are "Made in Japan"!!  I cringe when I see "Made in China"!!

1971-1973: '67 CL77 (305 Scrambler), Sold, because my wife said to...
2018: '14 CB500X, The dream bike of my youth!  Thanks, Son

Offline SilverCycle

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Re: Missing Engine Mounting Bolt
« Reply #46 on: Yesterday at 10:12:04 PM »
But do Honda make crash bars, or protection, for CB500X? I thought there was only an OEM light bar?

Online Aggie95

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Re: Missing Engine Mounting Bolt
« Reply #47 on: Today at 04:04:57 AM »
I don't know if Honda offers OEM crash bars.  I just assumed they do because timur said they do...  I bought my '14 with GIVI bars already installed.  I would hate to take them off; they have saved my bike a few times.  Seems like I am pretty good at dropping it.  I'm getting old and my balance is going to sh**!  I frequently put my foot down on something slick, or in a valley, or i try to take off on a hill in second or third gear, etc.  Anyway my GIVI bars have a lot of scratches on them that would have been on my pretty bike if the bars hadn't been present!

1971-1973: '67 CL77 (305 Scrambler), Sold, because my wife said to...
2018: '14 CB500X, The dream bike of my youth!  Thanks, Son

Offline timur

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Re: Missing Engine Mounting Bolt
« Reply #48 on: Today at 08:50:25 AM »
*Originally Posted by SilverCycle [+]
But do Honda make crash bars, or protection, for CB500X? I thought there was only an OEM light bar?
Well - IMHO these light bar has the same function that GIVI bars. And althought GIVI resembles more sturdy I'm doubtful that they protects better than Honda ones. The degree of protection of these bars depends on the resistance of their mounting points so the aesthetic appearance could be deceptive in this case.

Regards,

Timur

 


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