Hairline crack in engine lower casing at front left engine mount

[Erwin83]

Forum life: for better or worse right. I'm typing this as information and a 'warning' to other 350/400 owners:

As I mentioned in my other topic (http://www.sohc.co.uk/index.php/topic,21101.0.html), I did a frame-swap on my 350f.
Just a couple of evenings worth of tinkering, everything went smooth apart from getting the oil filter off, which required excessive force and destroying the oilfilter housing pipe-bolt. Luckily I had one in my pile of parts.

With almost everything back together, I thought it would be a good moment to finally take care of the small oil leak that my bike has had for the last years. There was always a drop, hanging from the oil drain plug. So I bought a new original drain plug seal, did the oil pump O-rings, new oil filter with O-rings, and gave everything a good clean, put oil back in..  Still a drop next day...  .

While researching in more detail, I spotted something that made my heart stop for a slight moment  ... A tiny hairline crack, just at the left front side of the engine, in the lower half of the block. Just behind the front left engine mount to be precise.

Well.. turns out I found the actual oil leak... Seems the bolt used in this engine mount, is slightly too long, and pushed the engine away from the mount, causing pressure in the aluminium and finally cracking the engine lower casing. Correct and too long bolt compared:
[ Guests cannot view attachments ]


Damnit! Thoughts like 'why didn't I feel this while tightening' and 'why didn't I check fitment before tightening' and 'why did I use that old bolt anyways' etc. But... that doesn't help, so I moved into problem solving mode. Like I said, the oil drip has been part of my CB since as long as I can remember having this 400 engine, so maybe it's good I finally find the cause.

With the bolt out (and pressure gone, the crack isn't visible anymore, not with the naked eye at least.
I wire brushed everything spotless, used a lot of degreaser and towels, went under with a good light source, put the bike nose-up high so the oil in the pan is in the back, and the leak stops.

As welding this is going to:
- require a full dismantle of the just assembled big-bore engine
- heat introduction may warp the casing.
- be a messy job, oil contaminated, old unknown alloy mix, no guarantee of actual solving it long term
- be costly as I certainly can't do that myself with my auto-mig spatter machine...
I made the choice to patch the leak with "Quiksteel 16402" epoxy aluminium. Seems to get extremely good results according to internet reviews, especially for events like this oil leak.

Job scheduled for this weekend...
Does anyone have advice or experience to share with regards to this sort of repair?

Will keep you updated.

[Erwin83]

Seems I'm not the only one. Yesterday evening I couldn't find any info, but must have used other English search words.
But this is very similar:

http://forums.sohc4.net/index.php?topic=173986.0

[Nurse Julie]

It is very common Erwin, members on this Forum have had this experience in the past. Mike the Bike comes to mind. You cannot ignore it and the best plan is to source a new set of replacement cases.

[Erwin83]

I read that too now! Strange I couldn't find anything while (still a bit shocked) searching on my iPad yesterday evening, and now I read about many people with this issue, caused by long bolts and/or crash bars.

Sourcing new cases is not something I will be doing anytime soon. That will certainly be a multi-year plan.
This bike isn't ever going to change owners anymore (or it will be from me to one of my kids), so for now, I will definitely patch it and as long as I can stop/limit the dripping, I'll leave it be and save the work for a next engine strip down.

[Laverda Dave]

I had exactly the same issue with my first 400/4 in 1980.  The PO had fitted a set of crash bars, they were rusty so I took them off and refitted the bolt without checking the length of the bolt first (I was 19 and thick!). It was 2mm longer than standard. Result, I had a slight oil drip and a hairline crack. I tried araldite without any success.  In the end I had to buy another engine although strangley enough this was from Frank of Classic Motorcycle fame in Greenford.  At the time in 1980 he was living at his parents in Ealing and breaking bikes in the garden shed!

[Bryanj]

If you can get a dremel in there V out the crack a bit to give the epoxy a better key plus use brake cleaner to clean. Iyts all worth a try instead of a rebuild especially as you have been living with it for years!

[awrawr]

Mine has a weld repair. Its held since 1980. Do you think I can stop worrying about it yet? [ Guests cannot view attachments ]

[mike the bike]

Yup.  Same thing on mine.  I bit the bullet and got it welded.   You only need to remove the bottom casing so it's not such a big job.

[Erwin83]

Quite impressed with the Quiksteel stuff. After mixing the 2 components, there's only 2 minutes before you feel it getting rigid, so there isn't a lot of time to apply it. That makes it a bit harder to get a visibly appealing job done, especially in the tight cravesses around the cooling ribs.
Nevertheless, I think I got it right.

Oh, and before starting to mix the material, of course extensively degreased (and I pulled part of the oil out and the bike with its nose up so there wasn't any new oil coming through). And I rubbed the surface with a hard metal wire brush, so the epoxy had a nice rough and paint-free surface to glue to.
I ended up completely encapsulating the nut of the engine mount bolt, as it was impossible to get a layer of material behind or next to the nut, while maintaining enough space for the nut to be removeable.

Not the prettiest of repairs, but happy if my oil drip is finally solved now for 20 euro's (and half the Quicksteel tube still on stock).
Fingers crossed that my garage floor will remain dry now.

[mike the bike]

Just remember to put the shorter bolt in that side and don't forget the spring washer or you'll be doing the job again.

[awrawr]

Where has the nut gone?

[Erwin83]

Just remember to put the shorter bolt in that side and don't forget the spring washer or you'll be doing the job again.

Yep, the longer bolts have found their way to the bin.

Where has the nut gone?

The nut is completely encapsulated by the Quiksteel. The crack is also inside the little nut-area (that's where the long bolt pushes), so in order to have material cover the crack I had to:
- Apply the Quikmetal in that tight area, covering all of the crack (mind, my finger doesnt fit there, so I used a small spatula, not ideal).
- Push the nut firmly in Quikmetal to avoid risk of the nut not fitting anymore altogether
- Screw the engine bolt in to make sure the nut was lined up correctly
(all this in 2 minutes)

I didn't like the result of this (hard to be sure I had decent coverage), so decided to cover the whole area with the nut inside.

Like I said, not the prettiest of solutions, but... so far she's dry.

[Tomb]

Won't oil eventually make its way up the bolt thread and leak out that end?

[Erwin83]

Won't oil eventually make its way up the bolt thread and leak out that end?

No, I don't think so.
There is space between the nut and the cracked surface, which I filled with Quikmetal.
However this space is tight, like 2-3 millimeters, so there was no physical way to patch it and keep the nut 'serviceable'.

Drawings are a top view (when laying on your back, looking up under the engine).
The Quikmetal patch now forms a layer between the cracked surface and the nut.

[Tomb]

Gotcha. Yep looks good.