Can small cracks inside the crankcase be treated with Silicone RTV gasket cement?

Question

I have separated the crankcase of my Honda CD200 Roadmaster. There are numerous minute cracks inside the crankcase. I dont think welding is necessary because the cracks are due to wearing from thousand miles of bad road. Can i cure the cracks using silicone RTV gasket makers? I have one on my shelf called Hardex. Would that be ok? cause the silicone stuff doesnt melt even on high temperatures.. Thank you.

Answer 1

if it don`t leak any oil just leave it as is

Answer 2

Are you sure your not just seeing casting marks? Does oil seep out at these locations? I would recommend against using and RTV sealant or JB weld inside the crankcase all it would take is a small amount to break loose and it could destroy the engine.

Answer 3

If they were,,,they would have opened through the surface  very shortly after their occurence.

They are also in Non-Stressed location.

Honda Castings,,,most j*p engine casting for that matter,,

Employ a design which is like an armature,,,or superstructure,,,framework,,skeleton,,,,... ya want to call it.

Observe the part and note all the Ribs,Webs,Beams,and so on.

You'll see than no crack extends into or across any of those..

The areas Between the superstructure are Thin,and Non-Structural.

They are like a "Skin".

Because they ARE open fissures,,,they WILL fail Zyglo Test.

(Flourescent Dye crack disclosure agent)

But you can go beyond that and inspect them under High Magnification and they will show surface textures of a Casting flaw,,,,

and not the grainy surface typically displayed by stress crack.

I've seen that 1000's of times over the years.

Long ago I became comfortable with them on In-Service engines/parts.

On Brand New Parts though,,,it's Still as Alarming as the 1st time I ever saw those "cracks"

If you remain  skeptical,,,consider this "common sense" appraisal.

#1,,an actual Stress Crack will not appear in a Surface,,,then extend itself across the WIDTH without traveling thru the section's Thickness.

Not Impossible,,but Almost impossible.

It WILL go thru the thickness very shortly,,before it gets much longer.

#2,,,if there is enough Force to initiate a Surface Crack on a Full-Section,Undamaged area,,,

Then there is PLENTY of force to quickly finish the damage it's started.

Cracks don't go half-way then STOP,,,,,

especially not when a Damaged Part is subject to SAme Force that started breaking it when the part was "good"..

If the Crack is "Half-Way THRU",,or however Deep,,,,

The effect of a Given Force is effectively MULTIPLIED by Reduced cross section/area of the crack.

Make sense?

If the metal WAS 2mm thick,,,and Routine Operation cracked it 10%~20% THRU or however much,,,

The Same Routine Operation will be even MORE influential on the damaged part.

It Snowballs in a downward spiral  towards ultimate failure.

The Worse it gets,,the Easier/Faster it gets worse.

A MONTH or 2 of daily riding is Usually enough to finish off a cracked aluminum casting due to stress.

Let alone 25 Years

As worrisome as it may appear,,

I seriously doubt you have any problem or need for concern.

No Harm in "sealing" it though especially if it make you feel more confident

Good Luck

Answer 4

use jb weld.   ive used it on a few different things and its worked excellent.  ive used it on a block, a radiator, and a head.

Answer 5

go to a boat store and get MARINE TEX putty. it is resistant to gas,oil, whatever and is so strong it can be machined.I have fixed engine cases with cracks using it many times succesfully.