From the very first to the very last T3 1200

Some time around 2000, Triumph completely redesigned the crankcases and cylinder head of the T3 1200 motor. They had already done a redesign on the cases a few years earlier, doing away with the inspection cover over the starter and alternator gears. That change is not good news for anyone who suffers from the famous broken sprag clutch problem. The final change seems to me to have brought a lot of the design ideas used on the T5 engines across to the 1200 four whilst retaining the same cam cover, timing cover and sump castings for some reason. The clutch, LH crank and sprocket covers are all completely different. 

 I had been looking out for a cheap late Trophy 1200 engine for a while, just to play with as much as anything. Well, eventually one turned up at a very reasonable price in grotty and 'as seen' condition. I just wanted something to strip it to see how Triumph finished off the T3s so the fact that it was ropey didn't worry me too much.

 From the RHS, the simpler construction is obvious. The head is visibly similar to the T595, with two external M6 bolts outboard of the camchain and vestigial finning. The clutch cover is also much simplified and incorporates the oil filler. Breathing is through the LH crank cover on these motors, rather than in the clutch cover. The sprocket cover is not longer oil bearing. A sight glass is fitted beneath it.

LHS of late motor, 'breathing' crank cover and oil sight glass.

 A wet black motor always looks new. Sadly, it wasn't quite as good on the inside.

The oil was very thick, almost treacle-like in consistency. On the other hand, I had expected to find a considerable amount of shrapnel in the sump. Not at all - just some aluminium shavings that looked to me as if they were left over from manufacture. And instant gasket, no doubt washed down from the head where it had been generously applied at some point.

 The internals looked pretty clean - no obvious signs of breakage or wear, just the treacly oil. The motor was not seized. I span it over on a starter and jump leads to test the sprags. They seemed fine but at this point it became clear that the engine had zero compression. It was easy to turn over by hand.

 I checked the valve clearances in case they had all closed up but they were all fine. So it was time to lift the cams and head.

 This is where things started to get hard. The cam cap bolts were incredibly tight. They are only supposed to be torqued to a modest figure (10 NM) but I was struggling to get them moving with a tommy bar on a 1/2inch socket. I broke three of my torx T30 bits doing this. In the end, I bought a special tough T30 bit from Screwfix and a new set of locking pliers. The worst ones were outboard of the camchain. These caps are particular important because the oil supply to the cams is delivered through them.

Cam bearing caps removed after a big fight, I can pull the valve buckets

Separate compartments in a sorter box to keep the buckets from being muddled up

I thought that had been hard. When it came to the main head bolts, it was going to get harder even though they accept a far more substantial torx bit. I'd had a clue that all was not well from looking into the block from the rear of the cylinders, through the rear water outlet. The cylinder liner I could see was very black and crusty. I couldn't understand why.

Cylinder head bolts in varying condition, centre right sheered off

The rear bolts were tight but not impossible. The front bolts were a nightmare. I was swinging on a one meter breaker bar to get them to turn. It was too much for two of the bolts which just sheered off. At least I could finally lift the head.

A very manky head gasket.

Cylinder 4, with broken head bolt visible top right.

Cylinders 3 and 2, broken bolt bottom left

The pistons are encrusted in oil and the head gasket in horrible condition.  The head on this engine incorporates passages for coolant and the gasket has holes to allow its movement.

The coolant passages in the head gasket are nearly all obstructed by crusty burnt oil, as are the passages in the head casting itself. The outside of the liners are encrusted in burnt oil. However, the cylinder bores look in really good condition - I can see the honing marks from manufacture on all of them. It seems to me as though oil from the head somehow got into the cylinders it blew through the water jacket. There was no obvious sign of oil around the jointed face outside of the engine. I'm guessing when the gasket went, it blew all of the coolant out of the bike. Must have been dramatic, to say the least.

The liners are very tight in the cases. I shall have to think carefully about how to free them off. I might try to drift them free from beneath, if I go ahead and split the cases.