Honda-SOHC

It lokks like Xylene is thd thinner for Granville paint. That's the same as Hammerite. I've ordered some of that too. Let's hope it works.

I coated the inside repairs with Evo-Stik epoxy metal. It's more liquid than the putty stuff so can be spread on easily. The idea is to cover any remaining cracks to prevent oil leaks.
I will still reinforce the outside with epoxy putty.

Well the top casing was much more difficult to weld. Durafix doest like vertical use. It just runs off into a large puddle. Its I also almost impossible to weld both sides of the casing. Heating up for the second weld just melts off the filler from the first. I went through a couple of rods before giving up.
My next attempt was better. I lifted the engine so the area to be welded was nearly horizontal. That gave a reasonable weld. Certainly strong enough for such a small area on the casing.
Having welded the inside of both cracks, I am going to reinforce the outside with epoxy putty. I use evostick putty. It's 2 parts of putty which you break off and nead together. I've used it before and it sets very hard. It can be sanded, filed, drilled and tapped. It also sticks to almost anything including hands so use gloves when handling it.
There's more room to use this on the outside. This should be the last step in the repair of the casings.
I would attach pictures but they're above the 3Mb limit on this forum.

Engine No. B750GE-1004112
I've had some good luck on this, I hope. Since TIG welding doesn't work, I decided to try some of these wonder rods that weld aluminium at low temperature. My local stockist (who I tend to trust to sell quality stuff) sells Durafix. Not cheap but worth a try. So far all I've done is tin the part that's broken off. The rods worked really well even at my first attempt. Having put a pool of Durafix on the metal, I ground it back with a power file. It's harder than the aluminium and certainly adhered well. Tomorrow I will try welding the pieces back together and let you know how it goes. Fingers crossed.
There's various video's of Durafix on Youtube.
Also, I have no connection with the company.

John

Well I've finally got the engine out and split. The bad news is there's the hole in the lower casting but the top casting us also cracked in 2 places.
I took the 2 parts along with the broken bits to my welder. He tried to weld it with a variety of rods but they spat everywhere and wouldn't make a run. He was using a TIG welder and is experienced. Does anyone know what sort of rods and gas work for this? Failing that, any recommendations for someone who can weld it? I'm near Abingdon in Oxfordshire.
My final option seems to be a second hand pair of casings. I've found a new pair for sale but at £2700+ they're eye wateringly expensive.
Thanks for the tip about cmsnl. I've downloaded all of their drawings.

Hi to everyone. I'm a new member having only just dicovered this forum. I don't like starting by asking for help but I've a problem.
I got my bike out for it's first ride of the year. It rode for a few yards and stopped. A piece of rag had tangled between the chain and front sproket. Then I made my big mistake. I slackened off the chain and tried to force the rag round the sprocket. I now have a big hole in my gearbox. The damage only seems to be to the bottom part of the casing.
It looks like it's engine out to repair this.
Can I split the gearbox bottom without a complete engine strip?
My repair options seem to be: rebuild the area with epoxy putty. Stick the broken bits back in with epoxy or get the casing welded. That is my favourite. I could get the casing built up with weld or weld the broken bits back in.
What do you guys think?
I'm a capable mechanic type but with little experience on bikes.
The rest of the bike is ok. I don't want to sell it and like the idea of keeping as many original parts as possible.
Thanks in advance
John