"CBX Book II" ... Con-Rod Warning!!

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cbxian
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"CBX Book II" ... Con-Rod Warning!!

Post by cbxian »

Hi Guys,

I want to put a piece of advice at the back of the "CBX Book II" regarding the dreaded 'hydraulic lock' when the Con-rod gets reshaped!! I need you Technically minded CBXers to comment on how I should word this, especially the "Solutions" below ...

A Final piece of Advice …
Having “been there and done that” I think it appropriate to give a repeated Warning to CBX Owners, as is detailed below in the letter from Honda to Dealers dated 15th November 1978. Honda came to realise that there was a problem when the CBX-Z was left parked on its side-stand with the petrol-tap “ON”. Be aware that fuel can leak down into the barrel, causing a catastrophe when you hit the ignition switch. This happened me recently in Hong Kong when a Mechanic inexperienced with the CBX called me saying “The engine has frozen. It was running fine this morning, now it is locked up!” The conversation went something like … Was it on the side-stand at lunchtime … “Yes”, is the petrol “ON” … “Yes”. A strip-down and survey revealed #2 rod was the shape of a banana … the CBX’s “Achilles’ Heel” strikes again!! This happens too easily so be AWARE!

Solutions:
- Always switch “OFF” the Petrol/Gas Tap when Bike is stopped.
- Upgrade the Fuel feed system with an automatic vacuum-type fuel valve (as directed by Honda in the attached letter).
- Before starting engine put the ‘Kill Switch’ to “OFF” and hit the ignition button to check if barrels are clear ... if the engine stops cranking, you know you have a problem (before you do a lot of damage!).”
.

Has anyone got any comments, or better suggestions for how to overcome this problem? Thanks for any help. Please keep it simple, I am not the most Technically-minded CBX Owner!!! Any advice for me?

Best, IAN (ian@netvigator.com)
*********************************************
Home : ian@ netvigator.com (www.cam-hk.com)
Work : ian@udi-hk.com (www.udi-hk.com)

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Re: "CBX Book II" ... Con-Rod Warning!!

Post by daves79x »

I think you have it covered, Ian. Just note that the starter will not bend the rod, so kill switch OFF is a good method to test. Also a strong smell of gas is a good indicator. In that case, just pull the plugs and crank engine to clear cylinder(s). Kill switch OFF, of course, since the spark will ignite any gas expelled. Number one is most common, but I've repaired a #6 hydrolock also.

Good advice to include in your book Ian. Looking forward to seeing it.

Dave

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Re: "CBX Book II" ... Con-Rod Warning!!

Post by EMS »

As the 1979 CBX is not universally known or recognized as a CBX-Z, maybe a reference should be made to that year and also "when not equipped with a vacuum shut-off valve" :think:

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Re: "CBX Book II" ... Con-Rod Warning!!

Post by PAUL N »

Hi All 1979 CBX 1000 Owners
I unfortunately got Hydraulic lock on my 79' CBX. I left it on the side stand with fuel on.Came out 1.5 hrs later pushed the starter motor and clunk bang starter jammed for a second then it started with a loud rattle from cylinder 1 or 2 not sure.I now will have to get the engine stripped to find out the damage.Will keep you posted.
PS I knew about this problem but I wasn't careful enough.Just bought my first CBX Last September and had only taken it for 3 spins.only 12k on clock.
Paul N-- Ireland

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Re: "CBX Book II" ... Con-Rod Warning!!

Post by NobleHops »

Ya, that's as real as real gets, we just finished a bike that had been hydrolocked. Definitely feel your pain Paul.
Nils Menten
Tucson, Arizona, USA '80 CBX, sort-of restored :-)

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Re: "CBX Book II" ... Con-Rod Warning!!

Post by hondaman160mph »

It's painful to hear about someone's CBX being
hydro locked. I have trained my brain to always
remember, key off = gas off.

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Re: "CBX Book II" ... Con-Rod Warning!!

Post by FalldownPhil »

That really stinks. Very sorry this happened to you.
The only thing to add is what Dave said in 2014, if
you first crank it with the kill switch in the kill position
and crank it, you will know that you have a cylinder full
of gas and it will not bend a rod as there is no fire in the
hole. The starter alone does not have enough poop to bend
a rod. The engine just won't turn over.
Best,
Phil
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to remember that your objective was to drain the swamp !!

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Re: "CBX Book II" ... Con-Rod Warning!!

Post by Crazy Canuck »

Does pulling the factory overflow drain arrangement prevent this? I've pulled mine assuming it does.
Forrest Miller :thumupp:

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Re: "CBX Book II" ... Con-Rod Warning!!

Post by NobleHops »

Crazy Canuck wrote:
Tue Mar 22, 2022 9:23 pm
Does pulling the factory overflow drain arrangement prevent this? I've pulled mine assuming it does.
Maybe it makes it less likely, but it could still happen, just with overflow in any single carb.
Nils Menten
Tucson, Arizona, USA '80 CBX, sort-of restored :-)

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Re: "CBX Book II" ... Con-Rod Warning!!

Post by daves79x »

I hope you mean by 'pulling the overflows' that you installed individual lines? Just leaving open bowl spigots is not a great idea with a hot engine.

Dave

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Re: "CBX Book II" ... Con-Rod Warning!!

Post by PAUL N »

NobleHops wrote:
Mon Mar 21, 2022 1:58 pm
Ya, that's as real as real gets, we just finished a bike that had been hydrolocked. Definitely feel your pain Paul.
Hi Nils
Many thanks for your reply Just wondering a few things
1.Cost of repair all in
2.How long did it take
3.What Damage was done
4.Would you advise any other work I should do when I have the engine stripped it has only 12k on the clock.
Much appreciated if you can advise on above
Paul N
Ireland

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Re: "CBX Book II" ... Con-Rod Warning!!

Post by PAUL N »

Hi All
Many thanks for your comments
Just wondering would you advise any improvements i should do when the engine is going to be stripped given that it has 12k on the clock.
Paul N

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Re: "CBX Book II" ... Con-Rod Warning!!

Post by PAUL N »

hondaman160mph wrote:
Tue Mar 22, 2022 9:52 am
It's painful to hear about someone's CBX being
hydro locked. I have trained my brain to always
remember, key off = gas off.
Your Right on training the Brain but mine got distracted when my friend offered to make me a cup of tea and I hadent seen him and his wife since before covid.
I am going to fit a cut off valve and maybe a pump to be sure
many thanks Hondaman160

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Re: "CBX Book II" ... Con-Rod Warning!!

Post by Syscrush »

PAUL N wrote:
Wed Mar 23, 2022 8:42 am
Just wondering would you advise any improvements i should do when the engine is going to be stripped given that it has 12k on the clock.
That depends on your goals and your budget.

Unless you're rebuilding yourself, your best bet is to try to find a shop that has rebuilt other CBXs and have them assess and offer you a menu of options. Share your thoughts and questions on this forum, as there is a wealth of knowledge here.

To replace a bent conrod, the cases will have to be split, and that means there will be a chance to review basically every part in the engine. Please start a thread in ENGINES: Maintenance, Performance, Parts Sources and you'll get plenty of helpful advice on what to replace, what to upgrade, and where to find stuff. Maybe some pointers for your mechanic, too.
Phil in Toronto
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Re: "CBX Book II" ... Con-Rod Warning!!

Post by CBX-tras »

There are two main ingredients at play here.
#1. Any liquid can not be compressed.
#2. Connecting rods are usually the weakest part of any motor and the CBX rods are some of the weakest designed rods.

If the cylinder has fuel in it, and the motor is rotated at a given rotational speed (with or without the ignition "on") the rod is going to be distorted. A little (will let you rotate the motor) or a LOT, which causes severe internal damage and the motor is "locked-up".
I've repaired at least 10 motors with bent rods, one bike had 3 damaged rods.

I tell any CBX owner that will listen:
* Turn the petcock "OFF" whenever the motor isn't running.
* Park the bike on the main stand. (The side stand is only there to let the rider dismount easily). This allows the fuel to drain if there is a malfunction. Especially on the '79 models with the center located drain manifold.
* Run the carbs dry at the end of the day's ride. If there's no fuel inside, there's nothing to attack the inner workings. This does two beneficial things.
1. Insures that the petcock is in good working order.
2. Maintaines the bike for long term or short term in-operation. (I've seen pilot jets compromised in less than 2 weeks.)

Last but not least - DO NOT trust the AFV to be your savior. The internal "rubber" components are made of the same material that the other carb parts are made of. It can and WILL fail with age and the type of fuel being used. If you get in the habit of turning the petcock "OFF" every time you stop, this won't happen.
All years of CBX petcocks can be rebuilt.

Shown here is an example of the "twisted column" effect on a CBX con rod.
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