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!

Tuesday, 16 April 2013

Engine in bits

After a week off to prepare myself, I stripped the engine. Bit frustrating taking the gearbox and primary drive out again!
Almost immediately, it was proven worth while. I took off the internal oil lines...

Note the big lump of split pin about to go through the oil pump? I reckon it must have caught in a corner, it fell out as I took the pipe off.

It turns out that the engine holds the centre stand on the bike too, which wasn't too welcome when, 10 minutes before leaving for work, I was left holding the engine whilst sitting on the rolling chassis to stop it falling over. Eventually I extracted myself and left it looking like a slain animal.

Next day I split the cases. Here is the RH side, dripping in shitty silicone:
 And the gunge still in the cases. Remember, this bike was sold as having a newly rebuilt engine. Maybe Barry the Bastard Butcher was too poor to buy rags and jizer?

Here is the big end, showing where the split pins to lock the nut aren't. Nuts were hand tight too.

 Bit more rod damage, it's definately scrap.

Oil pump hole blocked with silicone

The above is a strange one, it shows the feed plunger on the oil pump. Look carefully and you'll see the metal round the eye has splintered off. If you own an oil pump with a similar bike fitted, you might want to check it.

Today, I turned to the cylinder head. I needed to knock the valve guides out to measure them, and take out the studs etc for inspection/cleaning. When I turned one stud, it went like this:

Once removed, I found a hole at a funny angle with the remains of a stud in it

Someone has obviously snapped a stud, tried drilling it out with a hand drill and made a right mess. This is easily done-as soon as the drill gets a sniff of the soft ally, it'll chew through that instead of horrible hard steel. He's then drilled it on the piss anyway, rammed a new stud in with lots of threadlock, then bent it to vertical. The top hole in the pic had a straightforward stripped thread too, so this end of the rocker gear was not far from escaping.
To sort the broken stud abortion, I used a dremel and dentist burr type bit to cut the stud remains in two down the axis. They then fell out. Next, using an ancient hand pillar drill, I carefully cleaned the hole out with end mills. First, I used one only just touching the sides to level off the bottom. Then, I went bigger until the hole became round.

End mills and slot drills (milling cutters) are great for righting wonky holes. The flat end is less likely to follow the previous efforts, and having 3 or 4 flutes makes it much stronger. You have to be very delicate though, and be careful-my hand cranked pillar drill is good. Ideally you want a milling machine, but if you clamp it down well a regular electric pillar drill should be OK. Like I say, be delicate.
Hole is now tapped to a convenient size, in this case 7/16ths Whitworth. You could use whatever came close, metric would be fine. Just don't remove more than you need to, and stick to a coarse thread for ally-Whit, UNCF or Metric standard are good. If, like here, the hole has some of the original thread remaining, make sure it is removed. The next step is to fit a plug of ally, so you don't want the recreated hole to break through the side. Finally, I'll use the rocker block and the three good holes to mark out where this hole should to follow, if it works.