Honda CX 500 Forum banner
1 - 18 of 18 Posts

·
Registered
Joined
·
13 Posts
Discussion Starter · #1 ·
Motor vehicle Automotive tire Automotive exterior Gas Automotive wheel system

Water Grey Wood Automotive tire Tints and shades
Was torquing down my cylinder head and heard a loud pop… this is the right side front thread for my cylinder head bolts. Looking in I just see the rest of the thread. My engine block is ruined now isn’t it?

also, working on getting model of bike in my profile
 

·
Super Moderator
Joined
·
24,173 Posts
You forgot to clean the goop out of the hole is my guess and this is the result of hydrolocking in the bottom of the bolt hole.

I wouldn't say it's a boat anchor straight away if that is only the bottom of the threaded bolt hole.
 

·
Registered
Joined
·
13 Posts
Discussion Starter · #4 ·
Nice boat anchor.

What were you using to determine the torque on the bolts?
What torque value were you using?
Were the threads lubricated?
I’ll be honest I wasn’t using anything to determine torque, just spinning my wrench till the head of the bolt touched the rocker arm holder. Threads were lubricated. I should mention the the cylinder head on this side was missing for a few years and the threads were full of dirt from being exposed. I had PB blasted, scrubbed and blown them out.
My grandfather suggested JB weld but he’s a certified red neck mechanic so I thought I’d get some opinions
 

·
Registered
1981 CX500C
Joined
·
477 Posts
Well...... If it were my engine.....I'd replace the block at minimum.

Always clean the holes. The c-rap will collect in the bottom of the hole, then the bolt will compress the mess leading to break out.

Torque values are for DRY threads. The torque level must be reduced when the threads are lubricated. The amount of reduction depends on numerous factors.

You need to be using a torque wrench with the matching units for critical fasteners like head bolts.
 

·
Registered
Joined
·
438 Posts
if you can determine that the bottom of the hole doesnt mate up with either the coolant jacket or the oil gallery, it may be fine. if you have the missing piece, id jb weld it back on. if you dont, id fill the hole with rtv.
 

·
Super Moderator
Joined
·
24,173 Posts
I think that what you see is what it is - but must admit I don't know this for a certainty. I think that we are looking at the end of a blind bolt hole, no more.

I think that it will be below the coolant jacket so the potential possibility is that it's into the crankcase where the only pressure is crankcase pressure anyway.

But .... I think the damage is confined to the bolt hole which has broken to the path of least resistance - the outside.
 

·
Registered
1981 CX500C
Joined
·
477 Posts
I'm not saying its 100%, just that the other side should be checked.

Worst case. It was a fluid in the bottom of the hole. The fluid was pressurized as the bolt was cranked. The resulting hydraulic pressure of the fluid is exerted in all directions. Other areas of the case may have cracked prior or simultaneously as the piece was ejected from the case.

I still say the most sure path is to replace the block. Yeah, I know these are becoming scarce. But, there are many bikes in none running condition with good blocks.

OP, Good luck with whatever repair path you choose.
 

·
Registered
1981 CX500C
Joined
·
477 Posts
Sorry...yeah, I was probably a little quick with the "...boat anchor" comment.

Suitable repair maybe possible. Just need to verify the integrity of the other side of the case and if the water jacket is compromised.
 

·
Premium Member
1978 CX500 "The Grub", 1983 GL650I "Nimbus"
Joined
·
12,665 Posts
If you know a good welder, you could have that filled.
Bottom out the bolt in the hole (without the head, of course) to serve as a form. The new aluminum won't bond with it. Best to follow up with a blind tap.
 

·
Registered
Joined
·
2,900 Posts
What about the need to apply considerable head bolt torque repeatedly to a substantially compromised bolt hole?
Also, they’re not rare in my shop, recently I got zero bites at $25 @ for complete motors (sans carbs and starter) with radiator still mounted and full? 🤷🏻‍♂️
 

·
Registered
Joined
·
13 Posts
Discussion Starter · #16 ·
What about the need to apply considerable head bolt torque repeatedly to a substantially compromised bolt hole?
Also, they’re not rare in my shop, recently I got zero bites at $25 @ for complete motors (sans carbs and starter) with radiator still mounted and full? 🤷🏻‍♂️
Ok for $25 I can pay whatever shipping is to get it to California, radiator alone will run me close to $100, unless that was a typo and it's $250
 

·
Registered
Joined
·
2,900 Posts
$25 is the price, but the shipping cost would be high, it probably weighs over 175 lbs with the radiator. Local pickup only, I cannot crate it to ship.
Of the 4 I offered for sale, the $100 TAI motor sold and is running in the buyers bike afaik. The $50 CDI motor went into temporary service in my ‘81 Deluxe and is running great. A $25 CDI motor was stuck so I disassembled it to salvage internal parts (20k miles). The right cylinder was rusted in a “soft stuck”, not something I would work on. The last cheap CDI motor is still in the shop, rotates fine, low compression from sitting for years I’d guess, but charging stator fails static tests. Like real estate the three most important factors are Location, Location, and Location. I travel from New Haven, Ct to central Vt, so that 200 mile I-91 corridor can be “local pickup”.
 
1 - 18 of 18 Posts
Top