Wednesday, 24 April 2013

Going back together!

First things first, that head repair worked a treat.
To Recap: I drilled it back to round with milling cutters, then tapped out to a convenient size.
So, next step was turn up the new ally bushy. I could have used steel, which would be less likely to strip the thread. However, heat expansion might work it loose, and without a proper mill it'll be a swine to file flat. The file will chew away the soft ally instead of the steel.
If this had been a straightforward thread strip, I'd have drilled and tapped the bush on the lathe. Then, you use a lock nut and bolt to screw it in. If you look back, you'll see this wasn't. Instead, I machined it up then did NOT part it off-I took it out attached to the billet, applied loctite and screwed it in.

This shows the dog end of billet being chopped off somewhere near. Note the scrap ally plate protecting the casting from the saw, if you hold the saw against it it's much easier than praying you don't damage the preciuous things.

Bush filed flat, 4 dot punches to really lock it then a final flatten over the whole head with a lump of old grinding wheel (please note, NOT an offhand grinder!)

Finally, I used the rocker assembly to mark out the new hole, and drilled/tapped

On saturday, Nigel the owner came round, and we had a day cleaning and fettling the crankcases and head. By fortunate coincidence, a big parcel from hitchcocks came too.
I originally intended photoing every part and stage, both as a guide for whichever lonely crusader-owning soul stumbles across it and to show any future owners it's done properly. Then I got carried away...

Here is my preferred case fettling routine:

Wash in jizer
File off any burrs, damage, or the raised area round stud holes
Run a tap down threads, helicoiling as needed
Ensure oilways are cleaned out, pipe cleaners are handy
Wash on the grass with a hose
Wash with washing up liquid in the bath, using a powerful hot shower to blast out nooks and crannies
Pop in the oven on low heat till dry

If you're fitting bearings, cases need a good half hour until water/spit will fizzle straight off. Make sure all seals/spacers are to hand, and have suitable drifts in case the need some help. Finally, always drive on the outer race or you'll knacker it. I know it's obvious to most folk, but we were all beginners once.

Crank sat in case ready to reassemble

New rod has the later, stronger big end allen bolts. Torque up to 22 lb/ft. Another beginners tip-torque up one a bit (say, 5lb/ft), then the other, then a bity more until you get there.

Two more hints: roller bearings are a twat to put together, you have to sort of jiggle it about to get it right. I also should have checked the stud lengths, they seem to have shrunk! I think they were only in a bit, whereas I've put them in as deep as they'll go. Personally I think that is better as more thread=stronger, so I'll knock up a couple of new ones as needed. Running a die down them revealed a few more BSF to BSW threads (see previous!), so they'll get binned as I reckon they must be a fair way toward snapping.

Finally, one bottom end:

The bog roll tubes stop the rod clattering about and getting damaged.
Tomorrow I might post about my 2 new honda 400/4 projects. Parts that fit just right and bolts available at screwfix? Joy!

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