Monday, December 26, 2011

Engine teardown.

Just before Christmas, Peppe was finally able to take delivery of the engine and to start working on it.
We loaded it up on his van and then onto his operating table bike lift at the workshop, locked into an engine support.
Looking at it from this angle, I really appreciate the unit's smooth lines and thoughtful design. In my mind, whoever designed this did a really good job. Forget the naysayers who called it "power egg" and other such nonsense, this is a beautiful, sleek looking piece of design.

Here it is, looking lobotomised... kinda cool though, with all the oil dribbling out.

Alright, enough contemplation, let's get stuck in.

Look at him, he's practically gleeful!

Off comes the timing side cover, you can see the original contact breaker points...

...and the auto-advance mechanism behind that. Ingenious and effective. At the back you can see the gearbox mainshaft with the kickstart spring. There's something wrong there, I don't think that's the correct spring, and I don't think that locating tab should be there at all.

And here's the whole thing out. I'll keep this original Lucas part as a memento. Understand, there is nothing wrong with running points on our classics. In a way they can be a safer bet than electronics because even if they malfunction, you can usually get them going again with a screwdriver and a bit of sandpaper. If electronics blow, you're screwed (unless you carry a spare, which is a wise thing to do and takes up no room in your spares kit.). That said, knowing how immensely reliable Boyer-Bransden kits are, and how radically they transform these bikes, I'll be very happy to fit an electronic ignition on this bike.

This is the inside of the timing side cover, with the clutch actuation system visible. See how clean everything is? Normally these engines aren't this neat. Old oil cooks and stains the alloy, parts usually show sings of wear or tampering of some sort, not here. At first glance this appears to be a very unmolested engine.

The deeper we dig into this engine, the more it becomes apparent that this thing is in very good shape with very little wear. It probably would have run very sweetly just as it was - so why tear it apart you ask? well, keep reading and you'll see it was worth it.

Here's part of the kickstart mechanism. Look at those teeth, they're as good as new!

What I can only assume are kickstart pawls? Whatever they are, they're also in good shape.

The selector plate. Now, these are usually mangled, but on this one all the edges are sharp and straight, it's great!

This is what's under the second layer of the timing side. It's all business in here.

Notice how new this nut looks? Just one of the various clues to the good condition the engine is in.

Here's the oil pump. This is one of only two areas that gave us some pause. We'll get to that in a bit, in the meanwhile we'll leave it to enjoy a WD-40 soak...

Now for the actual timing gears: no two ways about it, if you want these off you're going to need some good pullers.

These are some very useful "separators", good for removing various types of stubborn bearings and, in this case, gears.

Now for the primary transmission side, again looking very clean (if you look past the oil).

A closer look at the alternator's rotor confirms something we suspected based on the engine's serial number: it's a 1969 model, making it one of the last in the Royal Star production.

If you look closely, you'll notice that the alternator wiring is secured with a soft aluminium strip: this was done at the factory and proves that the whole assembly has never been taken apart.

Above is the partially disassembled clutch: the basket and the hub show no signs of wear. The hub has never been opened but I must do that at least to check the condition of the shock-absorbing rubbers. I have a new set and I think it would be prudent to replace them. I've seen what can happen in there on other clutches when the shock absorber rubbers fail and it isn't pretty.

These two big nuts (tee hee!) secure the alternator's rotor onto the crankshaft. Again, look how new they are!

The rotor still holds a strong magnetic charge and the stator is also free of damage. This is a major bonus as I was almost certain I would have had to replace the alternator completely. Instead, I think this will work very well.

This shaky photo shows the back of the clutch basket. Smooth.

All teeth in perfect shape, both on the clutch and on the engine sprocket. The triplex chain is nice and tight and definitely over-engineered for this engine: it can easily cope with twice the horsepower.

This is the primary chain tension "slipper". These are normally all gouged out but this one has only minor scoring and there's plenty of meat left on it, so it'll be going back to work.
Yeah I know, my thumbs bend backwards, I hear it's a genetic thing... either you can or you can't.

The tensioner itself is adjusted by screwing that large bolt with a red plastic cap, in or out. The part that's exposed underneath the crankcase has a smooth metal cap screwed onto it to protect the threads: this is as rare as hen's teeth, either because people discarded them or lost them during maintenance or because they came loose and dropped off the bike when riding. I'll be keeping an eye on this.

Off comes the sprocket cover, to then remove the sprocket and, going back to the timing side, extract the gearbox.

This is truly a "cartridge type" gearbox, all internals can be extracted without leaving anything behind and without falling off in all directions and the sub-assembly can go back into the casing as one. To me, this is a better arrangement than that found on some Triumphs, especially the last ones. That said, I believe that the very first unit Triumph engines (the 3TA and 5TA) had a gearbox that could be lifted out in "one piece".
Again, take a look at those gears, brand new. Also, the bearings are so good, that I really don't think they need replacing. So I'm going to leave the entire gearbox as it is and put it back when we rebuild the engine. Ok, there is one thing I will change and it is the kickstart ratchet gear: on these engines it can sometimes get stuck, with the result that the actual kickstart lever will not budge. The very simple and easy thing to do is to put the bike in first and gently rock it forward by about |___| that much. That's all it takes to free up the ratchet. It only happens rarely but when it does, people who don't know how to handle it beat down on the lever with all their might and frustration, causing damage to the gear. That's what happened here.

This is the sump plate underneath the crankcase. It's fine, but there is a much improved version available from SRM here. I had it on the other BSA (below) and it is really useful when it comes to doing an oil change, not to mention that the bolt/plug has a really strong magnet that will attract any metal floating around in the oil. A small thing that can make a big difference to the life of your engine.

Ah, the camshaft! Also looking good, the lobes are even and without any signs of damage. The profile is very reasonable and according to period literature gives "zesty performance". By the way, whenever you read period literature you should always do so with a "1950s BBC radio announcer voice" it is SO much better.

These crankcases are filthy on the outside. There are dead spiders and spider nests there. It's going to take me a whole lot of solvents, degreasers and time to get these at least reasonably clean. Not looking forward to that but it has to be done.

And there's the crankshaft. Now comes something that's very important when dealing with these engine. The infamous sludge trap.

Getting the sludge trap plug unscrewed is a real pain in the arse: Peppe is not a small guy, yet he has to strike as hard as he can with a heavy steel mallet on a percussion screwdriver to get the plug to budge.

There is a great improved version available from the good people at Lowbrow Customs, here. And a helpful how-to, here.
Just take a look in there: despite this being a very good engine, in that it hasn't been mistreated, there is a lot of crap in there. This is why dismantling the engine was worth the work, in spite of the excellent condition of other components.
Sludge. This stuff is revolting and contains quite a bit of metal. It can easily block crucial oil passages, starving the big ends, which in turn can lead to catastrophic engine failure. Busted con-rods, exploding crankcases, a bad crash, serious injury or worse... Take care of your engine.

This is the actual trap, which sits in the crankshaft. It came out easily, though it can normally get totally stuck, making removal a nightmare. I cleaned it thoroughly and after refitting it and locking the plug back in place I promised the engine I would do regular and frequent oil changes and use a good oil with detergent properties.

Remember the oil pump? it was not turning freely as it should have so we took it apart to check the internals. The beauty of this thing is that you can replace every component if needed. In this case it all looked fine and it took a few tries to identify the culprit in the form of a swollen 'O'-ring that was causing too much friction. A new one solved the problem and the whole pump is now re-assembled and ready to go.

At the end of the disassembly we came up with what is really a very short and conservative list of spares needed.
After the holidays we'll put an order through to Supreme Motorcycles and SRM to get the parts we need, then we'll take the cylinder barrel to the machine shop to get re-bored. We're going up to the first re-bore just to be on the safe side. There is plenty of room and it will guarantee trouble-free operation once the engine is complete.
Once we have all the parts (from spares suppliers and machine shop) the engine will go back up in no time. Sure, putting things back together always takes longer than taking them apart, but in this case, seeing how good everything is, I would really be surprised if it took more than a day, day and a half.

Good job, man!