Removing Barrels & Stuck Cylinder Head From My Barn Find Triumph Bonneville T140 Project Engine | 04

In this episode having removed the engine and gearbox from my 1975 Triumph Bonneville T140V. I originally wanted to remove the head from the engine to inspect the combustion chambers and valves, but I found that the head would not come off the barrels. I am now going to remove the barrels along with the head so that I can try to get the head off using some different method. I bought this as a project bike, and registered it quite quickly in the UK using a V55/5 form.

Here are some of the tools I am going to be using for this bike:
Imperial Combination Spanner Set: https://ebay.us/gYz85M
Imperial 1/2inch Socket set: https://ebay.us/jylH05
Imperial Allen Hex Bit Sockets: https://ebay.us/iFV0OQ

Removing the barrels from an air cooled Bonneville Triumph T140 engine is relatively easy. It is held to the crankcases by 8 cylinder base nuts. There seems to be a number of different types of nuts that can be used to hold the barrels on, some requiring special tools because they are more like a star shape rather than a hexagon. In this case the nuts are plain hexagons. But interestingly they are quite tall, and I notice that the nuts couldn’t be removed without the barrels being loose as there would not be enough clearance for them to come out.

I initially loosen all of the nuts around the base of the barrels, and giving it a bit of a tug it was obvious that it wouldn’t just come loose, but I was pretty sure that it would come off using a well known technique. It may even be why the nuts are so tall. Basically, you undo the nuts until they touch the bottom fin of the barrel, then you work your way around turning each nut half a turn at a time, which then pushes the barrels off.

The nut technique worked very effectively, pushing the barrels up quite efficiently. Once I had the barrel nuts all off and the barrel loose, it still resisted coming off easily. I used the kick start to get the pistons moving down in the barrels, and once I had done this the barrel and head assembly came off quite easily.

Now that I had the barrels off I could give the bores and pistons a quick inspection, and at first sight they seem to be in good condition. There is now scoring or rust, and the barrels do have the much vaunted cross hatching that shows they haven’t suffered a lot of wear.

The next issue I was hoping to address was parting the cylinder head from the barrels. I had the idea of using more even heat, so I put them in the oven and heated them to around 110 degrees centigrade. I hoped that by using wood to protect the combustion chambers that I would be able to put enough force into my hammer blows to dislodge the head. Unfortunately it didn’t work, and the head still refuses to budge. I am contemplating trying to use a press to push the head off, but I am concerned that this might damage the head before it comes loose. So I am holding off from doing that for now.

Before moving on from the head and barrels I have decided to clean them so that I can measure the bores and the pistons, to see how much attention they might require. To clean the inside of the head and barrels I am using acetone, and when I poured it in the heat from the oven, it caused the acetone to boil. Apparently acetone boils at 56c, but the barrels and head soon cooled enough for the boiling to stop.

A couple of days later I noticed that the valves must be sealing quite well, as there was virtually no acetone leaking out of the combustion chamber. I have said before that this engine does seem to have had a lot of work done to it, with a lot of new parts. I suspect that the valves have been done which is why they are sealing so well. It would be a shame to damage the work that has been done because of the head being quite stuck on.

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