Topic: Crack inside crank case!!

[Mike-Quebec]

Hello everyone !!

As I'm freshly new to this forum, I must introduce my Honda project briefly!

I bought a barely functional Honda CB750F 1975, but all parts were there!

A strange noise coming from the engine when running was the start of the project! So, everything was remove from the frame and since I stand next to a pile of parts!

The fork, the brakes, the wheels, the top engine, etc are actually done, the frame with powder coat gloss black, etc...

NOW, I was at my last fight with a stuck bolt, this time in the crank case: penatrating oil, heat, nothing, so I use an bolt extractor.. nothing.. maybe with more force and ''SNAP''.. a crack on the primary shaft holder... @£*$%! ! I contact a professional welder I know and he can't do nothing for this..

What are my options? Here in Quebec from Canada, it's really really hard to have parts! Can I brazed it? Can I use epoxy? I want something strong as everything else!

Thanks for your help! Or watch if I part out my bike!

[BPellerine]

 pics would be nice,crankcases are not hard to find in canada,I live in nova scotia,so dont give up yet.bill

[Mike-Quebec]

Hi Bill !

The pictures are noted ''Attachments awaiting approval'', so I guess they will be available soon!

As for parts, yes I saw time to time parts but they are at a diamond price!! I can't justify buying a used, removed and non functional engine for 500-800$!

[enwri]

I think it used to be at least 4 posts before attachments would show.

[magnum56]

Put a "wanted" post up for a set of 750 cases here on the board.  (you won't want to mix and match upper and lower cases).

http://forums.sohc4.net/index.php/board,182.0.html

However, take full stock of everything else your current engine may still need. 
You may find getting an entire "runner" could actually be cost effective.

[Mike-Quebec]

Calj737,

There is not much bolt left in the hole; I drilled the bolt previously to insert the extractor. What has cracked, is the surrounding of the threaded hole. I hope my pictures will show, that should be more clear.

[Mike-Quebec]

Magnum56,

What may be the result by mixing and matching two different engine (top and lower case)? I've already rebuild the top end, the cylinder and piston..

[madmtnmotors]

What may be the result by mixing and matching two different engine (top and lower case)?

The case halves are "align bored" at the main bearings. The case halves are a matched set and should never be "co-mingled".

[754]

 Find a shop that does EDM bolt removal, they will get it out, for a few hundred or less.
 They can burn a hex hole into a broken thread, then insert an Allen  wrench and turn it out..

[Mike-Quebec]

Ok, I find a way to publish at least two pictures! You can see them upper!

[Don R]

Sorry to see that, replace the engine or cases. 

[BPellerine]

look in ontario,or quebec kijiji adds,or post a wanted add,one will come up,other years fit too.bill

[magnum56]

Yes ... that is BAD ... very BAD.

Do the "wanted" thing on all the various forums for the upper and lower case "halves", and anywhere else you can think of. 
The case halves haven't changed much (if any) for any of the 750 K and F versions.

Good luck. 

[754]

I am trying to imagine some scenario that would cause that, but can't think of one..
What does the other side look like  ? It might  end up being a display motor.

[PeWe]

Cases without drive chain damage
New cases will need new crank bearings. Old bearings must be bad, right?
Nothing to be reused even if new cases with same letters are found.
Time to replace primary chains + tensioner + cam chain + tensioner. Check all ball bearings. Primary hub might need new cush rubbers inside + new needle bearings?

Clutch must be good enough, can be replaced later on with engine mounted and no need to drain oil either.

Time to find another completely refurbished engine?

[Stev-o]

As cheap as motors are, I would just buy another.  And rebuild the top end as necessary...

[Mike-Quebec]

754,

The cause of the damage was me and only myself! I over torque the extractor tool, so before the tool snap, the aluminum case was more fragile so it brake... and let me with a very long face.

[Mike-Quebec]

To be honest, yes I was at the end of the project but I'm kind of tired of it. Each part I need take at least 1 month to come at my door when bought online. I think I will part out the bike for the happiness of anyone needs parts already rebuild!

 

[przjohn]

And so, another parts bike is born.

[Tom in Newcastle......Ontario]

https://www.kijiji.ca/v-motorcycle-parts-accessories/leamington/for-sale-cb-750-engine-lower-end/1285899907?enableSearchNavigationFlag=true

West end of Ontario ,but he might ship it 

[Tom in Newcastle......Ontario]

or

https://www.kijiji.ca/v-sport-bikes/ville-de-montreal/cb-750-engine-and-parts-for-sale/1286045258?enableSearchNavigationFlag=true

Ottawa

[disco]

Another example of why 'Ezy Outs' extractors should be avoided like the plague!

[westhewelder]

Welder here. It's do-able but your going to pay as much so weld and deck that as you will for a full motor. Check manitoba kijiji there's a bike graveyard and the guy will ship stuff.

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[The Lone Builder]

+1 to that!