Author Topic: Missing Engine Mounting Bolt  (Read 8380 times)

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Offline Falang

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Re: Missing Engine Mounting Bolt
Reply #50 on: June 30, 2020, 01:40:11 AM
Broken lower engine mounting bolts are a common problem when accessories are attached to the lower engine mounting points, and increased vibration is often reported. Lower crash bars and skid plates are known to crack the engine case in a collision, turning repairable damage into a write-off. For the CB500X, Honda does not make any accessories which attach to the lower engine mounting bolts. Honda only sell an upper crash bar for the CB500X.

Offline nicholas

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Re: Missing Engine Mounting Bolt
Reply #51 on: July 03, 2020, 03:29:45 PM
*Originally Posted by Aggie95 [+]
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).

if the bike is dropped ....is there a chance of braking the engine block supports?????

they seem quite sensitive to me...

Offline Falang

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Re: Missing Engine Mounting Bolt
Reply #52 on: July 04, 2020, 03:48:46 AM
*Originally Posted by nicholas [+]
if the bike is dropped ....is there a chance of braking the engine block supports?????they seem quite sensitive to me...

No, if there are no accessories attached to the lower engine mounting bolts. It is rare but it does happen with strong crash bars and skid plates which attach stiffly to the lower engine mounting bolts. These accessories make a CB500X more scratch-proof, but also more fragile. The problem with crash bars and skid plates on the CB500X is that the CB500X does not have a frame surrounding the engine, unlike, say, the Africa Twin, so most crash bars attach to the two highly-stressed and vibrating lower engine mounting bolts. There are three problems with this. 1. Increased vibration is reported with some models of crash bars. 2. Eventual engine mounting bolt breakage with crash bars which replace the Honda bolts with other bolts with incorrect dimensions or strength rating. 3. Rarely, but it does happen, engine case breakage in unlucky collisions where the impact that would have been spread out over the engine is is collected by a strong lower crash bar or skid plate and concentrated onto an engine mount, cracking the engine case.

Re #2, in order to install crash bars, some crash bars and skid plates replace Honda's high-tensile engine mounting bolts with longer bolts. These need to be custom-made high-tensile bolts which have the identical threaded length at the bottom of the bolt, but, say, a 5 mm longer shoulder at the top of the bolt (if, say, the crash bar lug is 5 mm thick). Off-the-shelf high-tensile bolts with those exact dimensions are almost impossible to find, so some accessory makers donít provide expensive custom-made replacement bolts of exactly the right dimensions and of high-tensile strength. Their substitute bolts eventually snap off or strip out. Some accessory-makers re-use the Honda bolts, which are too short to mount accessories (retaining the original spacers) and so the threads remaining in the engine case eventually strip. Other accessory-makers replace the Honda spacers with the crash bar mounting lug in order to re-use the strong Honda bolts and keep all the dimensions right. These bolts are unlikely to break. A few years ago, I bought a used 2013 CB500X, loaded with accessories. I was riding it hard to keep up with a macho pack of 1200 cc BMWs. While riding at full throttle, the lower right engine mounting bolt snapped off, resulting in hand-numbing vibration. I limped to Honda Bangkok and had it drilled out and repaired with a longer bolt and nut. Six months later, the lower left engine mounting bolt snapped off. Again I limped to a Honda Bangkok and had it drilled out and repaired with a longer bolt and nut.

Re #3, Honda Bangkok told me that they see many CB500Xs come in with snapped-off or stripped-out engine mounting bolts and with cracked engine casings, in every case caused by the installation of crash bars and skid plates on the bike. One owner installed a skid plate, took his bike off-road, and came down on a rock. Instead of absorbing the blow by breaking the cheap oil pan or denting the header pipes, one of the skid plate mounting bolts cracked his lower engine casing at the mounting point; a cheaply-repairable, nearly-new bike became an instant write-off. The CB500X is bulletproof until you start putting non-Honda accessories on it, and no Honda-made accessory attaches to the lower engine mounting bolts. The senior mechanic at Honda Bangkok advised me not to mount lower crash bars or a skid plate on a CB500X. I threw my 2013 crash bars out, and I do not have them on my 2019.

Last Edit: July 04, 2020, 03:51:14 AM by Falang

Offline nicholas

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Re: Missing Engine Mounting Bolt
Reply #53 on: July 09, 2020, 07:35:07 PM
totally agree with you.
about vibrations ....
if you unscrew any bolt from an engine mount the allignment of the frame to engine mounts is lost.

for beeing presice one needs to put a jack under the engine , unscrew bolt , keep in perfect allignment of engine mounts - frame holes  and torque to spec so that neither metal of engine mount / frame touches the bolt .
this is very improtand info

ive installed a couple of givi's to my friends cb500x's and no one one complained for vibrations.

i watched a guy at ytube with a red cb500x with sw motech.
he is from portugal.

in the video he says he dropped the bike twice with no damage to engine mounts / fairings even the bars them selves have just a scratch.

maybe thats why honda's genuine bars are made of aluminum??????????
to absorve any amount of energy ??????
all aftermarket ones are made of iron ....

what say you ?

Offline Falang

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Re: Missing Engine Mounting Bolt
Reply #54 on: July 10, 2020, 02:38:55 AM
Well, somethingís got to bend or break to absorb the kinetic energy when the crash bar takes a major hit, and it should be the accessories, not the engine case, that make the sacrifice. So they should be strong but not too strong, like the crumple zones in a carís bumper system. Or like a fuse in a wiring system.

For the Africa Twin, Honda makes crash plates and crash bars that clamp to the lower frame and thereby protect the engine by diverting blows to the frame.

The CB500X has no lower frame, so Honda does not make crash plates and lower crash bars. They make an upper crash bar which is not attached to those problematic (fragile and vibrating) lower engine mounting bolts. It is steel, but perhaps Honda has made the gauge thin enough and the pipes long enough to protect the engine by bending if need be to protect the bike from a major hit. Unfortunately it is expensive and it is not sold by Honda in Thailand.

Offline nicholas

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Re: Missing Engine Mounting Bolt
Reply #55 on: July 10, 2020, 07:56:21 AM
*Originally Posted by Falang [+]
Well, somethingís got to bend or break to absorb the kinetic energy when the crash bar takes a major hit, and it should be the accessories, not the engine case, that make the sacrifice. So they should be strong but not too strong, like the crumple zones in a carís bumper system. Or like a fuse in a wiring system.

For the Africa Twin, Honda makes crash plates and crash bars that clamp to the lower frame and thereby protect the engine by diverting blows to the frame.

The CB500X has no lower frame, so Honda does not make crash plates and lower crash bars. They make an upper crash bar which is not attached to those problematic (fragile and vibrating) lower engine mounting bolts. It is steel, but perhaps Honda has made the gauge thin enough and the pipes long enough to protect the engine by bending if need be to protect the bike from a major hit. Unfortunately it is expensive and it is not sold by Honda in Thailand.
+1

Offline Swanny

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Re: Missing Engine Mounting Bolt
Reply #56 on: July 10, 2020, 12:11:19 PM
Yea makes sense to me  :028:
Life... It's Just a Ride  :305:

Offline Swanny

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Re: Missing Engine Mounting Bolt
Reply #57 on: July 12, 2020, 08:56:58 PM
Look at the mounting points on the genuine upper crash bars

Life... It's Just a Ride  :305:

Offline motorboy

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Re: Missing Engine Mounting Bolt
Reply #58 on: July 13, 2020, 03:46:04 PM
*Originally Posted by Swanny [+]
Look at the mounting points on the genuine upper crash bars


I think Honda knows better don't they call it a light bar with no mention of the word crash
It's not a big motorcycle just a groovy little motorbike

Offline Swanny

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Re: Missing Engine Mounting Bolt
Reply #59 on: July 13, 2020, 06:47:52 PM
Yea they do. I want one but not impressed with the price  :156:
Life... It's Just a Ride  :305:

 



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