Hi guys, I’ve been asked by a friend to build a 1978 750 Bonneville engine that arrived in bits but had most of the renewables renewed and ready to assemble. My first dilemma was the rotor sticking out the back of the stator by about 4 mm. It would appear that this is normal and nothing to worry about, in fact moving it out flush with the windings meant the timing pointer fouled it. I eventually moved onto the head, lapped the valves in, placed the spring cups over the guides and noticed how high they sat. Once the springs and collets was fitted the spring looked overly compressed and would surely be coil bound in use. Check out the photo, I took it apart and flipped the cup over and the assembly went together better except every other engine I’ve built the spring sits in the cup not on it. The manual is useless, not a good picture of the spring cup orientation so I’m asking you guys. Do I have the wrong cups or is this another Triumph querk. All the ones I’ve seen for sale look the same as these ones, machined and not just pressed steel.
Hi Geoff, T140 and T120 heads are totally different as the cups all have different numbers and specs, as can be seen in your pic the bottom cup is not sat on the head and this is the cause of the valve bind, i'm no expert with the later engines as i only work with the earlier motors in general but you could first check if the valve guides are the problem or the bottom cup is correct as its not allowing the cup to sit down correctly.
Wotcha Geoff and welcome. As darkman has said all models have different specs so it's important to have the correct parts catalogue for the model you are working on. The parts catalogues are easily obtainable here: https://partsbooks.britishonly.com/ look down the list for your model and download. Unfortunately, in your case, the parts are already in the box so it's pretty difficult without accurate spec sizes to know if you have the right part. Check the date stamp or part number stamp on the head, this should help with making sure the correct parts are ordered. Are you sure you haven't mixed the cups? Have you put the top cup in the bottom? Have a peek at this, it has some valve spec sizes and helpful pictures. Please get back to us and let us know how you get on as we are all learning.
Thanks very much for the replies, I suspected something was not correct but having been given a pile of bits you are never quite sure where the error lies. Anyway, a friend just brought round a spare head and the spring cups were very different. The correct one for this head is the one on the right.
Hello Geoff and welcome to the forum Thanks for letting us know the outcome of your problem and good luck with the rest of the rebuild.
Hi Geoff and welcome to the forum happy you sorted the cup issue, looking forward to seeing the project evolve
Greetings, Geoff, and welcome to the forum! As you can see, there are lots of knowledgeable and helpful folks on here. Hope you enjoy the forum.
