Hole in bottom crankcase

[fryerk]

Hi all
I have just bought a 400/4 from a deceased estate which is in pretty good shape having undergone partial restoration by the previous owner before he passed away. The big issue with it is that he seems to have used an over length bolt on the lower left engine mount which has pierced the lower crankcase. I have tried repairing it using the metal epoxy but it's still leaking badly.
So my question is can I change the lower crankcase without a total stripdown or is it possible to invert the engine and remove the lower crankcase without removing the barrels head and cam etc.
If not then I guess I either go for a complete rebuilt (not really keen on that option) or look for a replacement motor.
Kevin

[hairygit]

You CANNOT just fit another lower crankcase, they are machined as matched pairs, and must be replaced as a matched pair. However, you can remove the bottom crankcase by inverting the engine and have it repaired by welding. A good welder will make any repair almost invisible, and once painted will not show. Not cheap though!

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[mike the bike]

Been there myself.  The lower engine mounting bolts are different sizes,  one being 2mm shorter,  so that it doesn't punch a hole through to the oil gallery.  I had to strip the engine apart and get it welded.  Splitting the crankcases isn't such a bastard as you might imagine.  The barrels, head etc can remain in place, just remove the lower crankcase with the engine upside down.  Of course,  the clutch, oil pump and gear shifting mechanism has all got to come off.  It's a good few hours work,  it all depends on your skill level or confidence,  don't forget the manual and plenty of hob nobs.

Let us know how you get on.

[fryerk]

Will do, at least it doesn't seem quite as onerous a task as I first thought. Thanks for your advice.

[Bryanj]

And while you are in there free off the notorious cam chain tensioner

[Laverda Dave]

This is how my 400 engine rebuild journey started!  When I was 17 I traded in my CB200 for a s/h 400/4 from D&H Motorcycles in Acton.
It was a great bike, a red F model. It was previously owned by an older gent who had fitted a huge barn door fairing, massive top box and suitcase sized panniers complete with front and rear crashbars. I removed all of it within a couple of days including the front crashbar.
I replaced the bolt and went for a ride, when I arrived home the engine was smothered in oil.  The crashbar mounting bolt had replaced the original lower engine mounting bolt and was slightly longer to take into account the 3mm crashbar mounting lug. it was too long and split the lower engine case when I replaced it although I didn't notice at the time.
I tried the epoxy glue, liquid metal, chewing gum, body filler method and nothing worked.  I ended up buying a s/h engine from Frank in Ealing when he used to break bikes in a garden shed!
6 months and many miles later I took the engine apart to replace the cam chain on the dinning room table (the tin of linklife chain lube was boiling up on the gas stove and the cylinder head replaced the leg of lamb in the oven at the same time).