Cracked motorcycle crankcase

[Wedg1e]

Only meant a small hole lol anyway was just an idea, as thats what ive always been under the impression is the best way to deal with cracks in things, stops them spreading as you weld along it. I'll take your word for it if doesnt work with castings, dont know myself as ive never had the pleasure of repairing cracks in castings

No, I agree with the principle (it works in fibreglass anyway), I just thought you wouldn't want any more holes than you started with, especially if they would let the engine oil out

 

[norlander]

[quote/

(Not wishing to sound an **** but it's Shox Dr. As there is "another" that stole the nickname all be it turning around.)[/quote]

My apologies sir.

 

[jordan1]

How are you going to clean the inside of the case then?

The engine is assembled, oil drained. Had hoped to 'V' the crack out & weld. The concern is about any oil that may still be inside.

 

[jordan1]

I

The engine is stripped right down isn't it ? You're not trying to weld it in situ ?

It is still assembled, if I had to strip it all down I would probably just get a s/h crankcase half.

 

[ronan]

I

It is still assembled, if I had to strip it all down I would probably just get a s/h crankcase half.

Might be the easiest way out of it.

 

[jordan1]

Might be the easiest way out of it.

I would just like to attempt a repair if there was not likely to be an internal combustion issue, damage to seals etc. I could possibly flush it out first.

 

[BrokenBiker]

i cant see how you would get it clean enough with it still all assembled, and how would you clean up the back of the weld to check for porosity?

 

[Pete.]

You can - I've done it. Hotrodder welded it. Any porosity and it would leak but mine didn't either time.

 

[Shox Dr]

If its stripped why do you not want to weld it apart? Distorsion? Better to clamp it down to a lump of plate

 

[brightspark]

I

It is still assembled, if I had to strip it all down I would probably just get a s/h crankcase half.

dont u normaly get them in a matched pair ?? not just one half

 

[rich the mechanic]

I don't know if it works for alloy but a trick an old Triumph sidecar racer I know used to use on cast iron parts was to boil them in a pan with washing powder he reconed that was the way to get the embedded oil out, obviously need a big pot for an engine case.

 

[lshigham]

dont u normaly get them in a matched pair ?? not just one half

Correct. I know people who have got away with running mis matched pairs but it's not worth the risk, they are line bored as a pair and meant to stay together

 

[Liquid Metal]

When i mentioned about perhaps drilling a small hole at either end of the crack, I forgot to mention............ You dont need to go all the way through the casing with the drill, only deep enough that the crack can no longer be seen. Just like when you widen the crack with a grinder to achieve adequate penetration.
Unless the crack goes all the way through.
Sorry should have been a bit clearer about what i meant before

 

[chevy2]

I do ali welding for a mate that runs a motorcycle repair shop,

Bit of a lottery what stuff welds better than others,
Did a ali fairing frame from a Buell, real junk to weld,
Did an engine side case from an early 70s Kawasaki and with virtually no prep it welded like new material,
You will find you'll need to use more ac balance cleaning than with most other stuff.

 

[jordan1]

dont u normaly get them in a matched pair ?? not just one half

Not that I'm aware, I've replaced damaged half crankcases before when there wasn't an option, without any problem

 

[Pete.]

Horizontally split cases are usually machined as an assembly, vertically not so important, probably not even possible.

 

[jinjahbiscuit]

It is possible and they are. More modern machinery is much more accurately made than old Triumphs and BSA's for instance, which is why you might get away with mis matched cases on the newer stuff.
Probably best to strip the engine before welding though.

 

[Pete.]

I'd like to see someone bore a blind bearing pocket inside a vertically-split case that's bolted to it's pair

 

[Shox Dr]

I'd like to see someone bore a blind bearing pocket inside a vertically-split case that's bolted to it's pair

It's the crank bearing surfaces that are or were, machined as a pair, not fitments within the gearbox

 

[Pete.]

What we on about here horizontal or vertical split? My take on it is that on a horizontal split case they would bore them all on one setup our struggle with the shell bearing tolerances. On a vertical split you're not interrupting any cut and a cnc could comfortably machine the two sides separately.