Fixing engine covers with Durafix

**erik** · 12th April 2008, 21:09

Ages ago (in september '06) I had an off in the corromandel and made a hole in the LH crankcase cover.

It had been in a slide at taupo before and I think my bike's previous owner might've damaged it as well, so I guess it did well to last that long. Anyway, I made a patch and DEATH_INC welded it on for me.

He said he had a hell of a time welding it on because the alloy has a high magnesium content, I think. The cover slowly seeped oil, on a long ride my boot got oily.

I aquired a spare parts bike with a cover in slightly better condition, but it had a few scratches, a couple of hairline cracks and the inside was marked from the end of the crankshaft bolt.

[edit: post split into 3 to allow enough embedded images (they're only thumbnails so hopefully it's ok)]

**McJim** · 12th April 2008, 21:24

Frankly I'm amazed that ol' bandit of yours is still running. Well done.

**erik** · 12th April 2008, 21:56

I wanted to fix the cracks and reinforce it so it'd survive another slide. I made a bowl shaped patch out of 3mm alluminium.

durafixed it on.

swapped it for the old patched cover.

That was all done on the 23rd of march this year.

**erik** · 12th April 2008, 21:59

So on the 4th of april, I went to a trackday at Taupo to test it (ok, testing it was actually an accident):

It worked a treat, the bike slid a fair way and the cover didn't break! It didn't even wear right through the 3mm ally patch. I was able to ride the rest of the sessions and then ride home afterwards (the gear lever push rod broke, but Meekey_Mouse gave me a spare RG150 one she had).

Just today, I've gone and put another smaller patch over the bit that ground away, it should be able to slide really far now before it wears through...

Hopefully I don't get to test it.

The durafix is kind of weird stuff to work with. More like soldering than welding (steel anyway, I've never tried welding aluminium). Even just using a MAP torch, I noticed the cover starting to bubble in a couple of places, I guess from the magnesium content (or an air bubble in the casting?). My first attempt with durafix was to mend the clutch cover that I damaged at taupo last year, it'd cracked right to the edge. I tried to bevel the crack so that I could get the durafix to flow into it, but I think it was the wrong approach.

I should have just put the durafix over the top. It's sitting under the bench downstairs looking rather messy.

I was using a propane/butane torch from mitre10, now I've got a MAP torch that is a fair bit hotter and works better. Maybe I'll have a go at tidying it up one day (probably only if I really have to).