Another Cracked Engine Case Question

[abyssmaltailgate]

I've been meaning do deal with this awhile, and believe I've found a solution, but decided I'd review the forum to see what information I could find out there (if any) about a crack in this particular spot of the upper engine case:



Obviously that top case is upside down, but this hairline crack extends from the portion of the case that meets with the primary drive (left hand) cover to the where the gear selector drum articulates in the left hand side of the case. My assumption is this crack possibly occurred after a lot of hard, clunky shifting.

My question is twofold: the first regarding how to repair the crack, and the second addressing how to potentially avoid future cracking.

In regards to repairing the crack, I was thinking about TIG welding the aluminum at about 20 - 30 volts with maybe a little bit of pulse since I know how easily engine cases (and aluminum in general) will liquefy; I'd use some pretty skinny filler rod too. Additionally, I'm used to repairing cracks in cast steel by drilling holes at each end of the crack so they don't grow while welding or after welding (due to incomplete fusion). I'm not sure if that's a wise idea here. Furthermore, I'm concerned if welding the crack in the first place is smart. Potentially, I'd assume there's a risk of melting and clogging local internal oil galleries and the metal expanding and shrinking, pinching the bearings where the gear selector drum articulates. Lastly, if I drill it in attempt to stop the crack, will I mess up the cases even more?

Basically, what I'm asking is 1) is it worth welding the case in this location and 2) should I drill the ends of the crack or just weld over the crack if I do weld it?

Finally, pertaining to preventing the crack in the future; this engine is a '74 XS650 B and came stock with a two-piece clutch push rod (at least that's what I removed when I stripped it). I've got a one-piece push rod I intend to install when I ultimately rebuild it. I understand the one-piece rod has smoother shifting action... I guess I'm hoping to confirm the one-piece may better protect the cases from clunky shifting and cracking better than the two-piece?

I'm looking forward to all you gurus and other shade tree mechanics chiming in...

 

[fredintoon]

Hi abyssmaltailgate,
Can you use the cases "as is"?
Have you considered vapor-degreasing the cases and sealing the cracks with epoxy?
Are you prepared to risk locally melting &/or warping the cases as you weld?
Can you find a replacement set of cases in better shape?
What have you got to lose?

 

[abyssmaltailgate]

All good points Fred. I have considered running the cases as is, but I'm not sure how well they'll hold up, which is one reason why I'm looking for feedback in this thread. Any thoughts on that? And I have considered epoxy, but I'm also not sure that will stop the crack from growing if it's exposed to the same stress... with that said sometimes when things crack, it occurs at a natural weak point and repair is unnecessary since the flaw has gone away (this kind of thing occurs on wooden instruments a lot like clarinets and oboes... I grew up in a musical family haha).

I do have a spare set of cases; however, the locating pins for the crank need to be repaired since they are all too recessed :-/ You're right though, I would be more willing to take the risk If I had a good set of back ups.

 

[johnnyc14]

It's hard to tell by the pictures but it looks like the crack extends into a bearing bore. If that's the case repairing the cases would involve removing the bearing, welding the crack and re-machining the bore for the bearing.

There is a great video by Jody at weldingtipsandtricks.com on tig welding a cast aluminum housing here.

http://www.weldingtipsandtricks.com/cast-aluminum-welding.html

 

[MaxPete]

I may be way off here Abyssmal (what a great name!!) - but I have a chain master link fail on my old '75 XS650B back in the 1970's while riding at highway speed and when the chain flew off, it cracked the case right above where the clutch cable enters the case. I actually got a new master link at a farm supply place and road the bike hundreds of miles home - and then a friend who was an excellent welder TIG welded the broken off piece back in place. That repair worked great for a long time afterwards (I eventualy traded the bike in on a GS850G) - and so the welding idea might be OK.

Pete

 

[fredintoon]

- - - I do have a spare set of cases; however, the locating pins for the crank need to be repaired since they are all too recessed :-/ You're right though, I would be more willing to take the risk If I had a good set of back ups.

Hi abyssmaltailgate,
What I'd try would be to reassemble the engine with the cases "as is" in the hope that it'd last until I'd found a GOOD set of cases.
Then swap the motor into the good cases and take time to decide if either of your existing case sets are worth fixing.

 

[abyssmaltailgate]

It's hard to tell by the pictures but it looks like the crack extends into a bearing bore. If that's the case repairing the cases would involve removing the bearing, welding the crack and re-machining the bore for the bearing.

You're right, it's hard to tell, but I'm pretty positive it wraps around into the bore.

Now, I'm not 100% certain, but from looking at the case and some other pictures I've seen of cases without the bearing in place, I think that the bearing just pops out... I say that because the case and bearing are dissimilar metals. I'm going to do some more research, but I'm thinking I can knock out the bearing, drill some small holes, throw a Hail Mary and weld the crack, grind down excess filler with a Dremel, then tap the bearing back in with some Threebond along the edges without any machining (sort of like the starter motor delete trick with a blanking plug).

 

[Brassneck]

Not sure if it's an option, but what about using aluminum brazing rods to seal the crack?

 

[Paul Sutton]

Get some dye for crack detection. It will show up exactly where the crack goes. If it wraps around the bearing housing then be cautious about reassembling the engine without making a repair. This bearing takes a big load and if the casing fails then you could do a lot of damage to the engine and maybe yourself. I would get a specialist aluminium welder to do the repair. It will cost and the housing may need to be machined out, but it may be the safest solution. Otherwise try to get a second hand casing (Ebay).

 

[abyssmaltailgate]

Get some dye for crack detection. It will show up exactly where the crack goes. If it wraps around the bearing housing then be cautious about reassembling the engine without making a repair. This bearing takes a big load and if the casing fails then you could do a lot of damage to the engine and maybe yourself. I would get a specialist aluminium welder to do the repair. It will cost and the housing may need to be machined out, but it may be the safest solution. Otherwise try to get a second hand casing (Ebay).

Thanks Paul. I thought it needed to be addressed rather than ignored. After some contemplation, I figured I'd play it safe, did as you suggested, and bought a spare set of cases on Ebay. They're allegedly in good condition (we'll see when they arrive). Fortunately they were only $62... it's funny, if this were a Harley, it'd be less expensive to have the case repaired rather than tracking down and purchasing a new set.

Additionally, now that I have a back up, I'm going to attempt to do the repair myself. I'm in training at a school for welding, so not only do we have access to all the equipment, I've got peers that might be able to help me if I screw up. Since I'll have new cases, this won't be a priority, but I'll try to update the thread with pictures and posts. Thanks for everyone's two cents!

 

[MaxPete]

Hey Abyssmal - that training is going to be very handy and if you can fix those cases, they may be useful for your next project!

 

[gggGary]

I think maxpete called it; chain slipping a tooth on front sprocket, I have a couple of cases with those cracks. There was at least one member that did the weld the crack repair and it worked for him.

 

[abyssmaltailgate]

It's amazing how many spare parts you end with when doing a complete rebuild of both the engine AND the bike... with all the leftovers from parts bikes I'm already tempted to start building another and I haven't even finished my first!

 

[xjwmx]

Somewhere in your town is an old, established motorcycle repair and customizing shop, maybe with a racing team, that has a genius aluminum welder with his own little cubby hole corner. I would get the case half really clean and then take it over there and talk about it.

 

[gggGary]

wandering the swap meet at Barber there was a BSA primary cover that had been bashed and beautifully TIG welded, could hardly tell it from factory.
Except the cover, placed gasket face down on the table, rocked a good 1/2" LOL

 

[abyssmaltailgate]

Well, here's the first step of the process:
I knocked out the bearing by amply heating up both sides of the case with a heat gun, spraying each side with some PB Blaster, then I whacking it with a claw hammer using a 5/8" chopper axle wrapped in a rag as a punch. Took about 10 minutes since I was trying to be careful hahaha, but everything came out unscathed! Here are pictures of the bore with and without the flash:

Anyway, I can already see that the crack wraps around the bore; however, it's not terribly deep into the case, only into that top portion of the left-hand side of the case that's sort of like a covers. Next time I'm at the weld supply shop, I'll pick up some dye and developer so I'll really be able to see the true size of the crack.

 

[Jan_P]

I think maxpete called it; chain slipping a tooth on front sprocket, I have a couple of cases with those cracks. There was at least one member that did the weld the crack repair and it worked for him.

Gentlemen I would be interested in more info about this.
My chain link broke and smashed into the part where the Outgoing axle seal sits.
So there is a small leakage inside of the seal. Nothing major . But it is not good being nervous of having no oil in the engine
But since I got other problems I took the engine out.
And installed another rebuilt motor. During that rebuild I got information that changes the evaluation of the first engine.

The leaking engine does not really need a tear down and major overhaul. At this point in time If I could stop the leaking and perhaps a top job.
Checking valves and so .
It would be much simpler cheaper and faster. Job
I have tried epoxy at least 2 times : Not working.
I own three welders including a TIG welder that is of the right type for welding aluminium.
Newer done it though . And rarely welds nowadays. I Worked with sheet metal in the Seventies and then was good at it. ( welding ).
I bought another casing on e -bay since i believed I would need to do it.So I have one
If I could put a spot with the TIG at the right place getting it tight. Not sure if it is accessible without tearing down.
But if teardown i might as well use the replacement and not weld at all.
I dont think it is a Load carrying position and behind the seal.

I know it is a bit of Substandard thing to do .But it would save time money and job.
Here are extremely experienced people might even be people who welds professionally.
As I recall it in the 70 ies not many could weld Aluminium at all .In Stockholm there was a company that did it for aeroplanes .
And at times för Motorcycle parts. But I believe it was a need för preheating and with special skills for the person who did it.
I believe with Acetylene.
As for welding in general it usually reduces strength ( more or less ) of the welded part so I Would not use it on a Motorcycle at places where
a failure can result in an Traffic Accident with personal injuries.

Please give info if better solutions JB Weld is mentioned is that any good?
AS well as info on the Thread starters project progress
And regarding Aluminum welding in general .methods filler and so.What to DO and what not to DO
I have seen it on parts like engine covers mostly with not so good results. But used.

If repair is possible without tear down .It would save a lot of money and getting the bike on the road.
Here the shop cost for such a repair tear down and rebuild would make it so expensive .That it would be regarded as scrap.








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[LilyVictoria]

Well, here's the first step of the process:
View attachment 89691 I knocked out the bearing by amply heating up both sides of the case with a heat gun, spraying each side with some PB Blaster, then I whacking it with a claw hammer using a 5/8" chopper axle wrapped in a rag as a punch. Took about 10 minutes since I was trying to be careful hahaha, but everything came out unscathed! Here are pictures of the bore with and without the flash:View attachment 89692 View attachment 89693

Anyway, I can already see that the crack wraps around the bore; however, it's not terribly deep into the case, only into that top portion of the left-hand side of the case that's sort of like a covers. Next time I'm at the weld supply shop, I'll pick up some dye and developer so I'll really be able to see the true size of the crack.

Thank you for these instructions. I really needed them.

 

[Raymond]

Hi @LilyVictoria welcome to the forum. This is an old thread but why doncha start a new thread and tell us about your project? This lot like plenty photos . . .

Cheers, Raymond