After spending so much time on the cycle parts, I fancied a change from painting things black! Also, as my workshop is so small, I really need to free up some floorspace currently taken up by engine and 3 boxes of assorted engine parts. So it made sense to move on to the engine rebuild next. That way, I can reinstall it in the frame and free up some space.
A bit of history to set the context: when I bought the bike, I was told that it had been taken off the road about 40 years ago to have engine work undertaken but then never put back together. I received the engine loosely bolted together and loads of bits in various boxes. As an example, the crankshaft and gearbox content were out in loose assemblies. The conrod was in a box of assorted bits.
Once I started to look over it, it became apparent that most of the engine reconditioning work had been done already all those years ago. So the crank has been reground and new bearing shells fitted to the con rod, together with a new little end bush and new gudgeon pin. There's a new +30thou piston and rings and the barrel has been rebored. There was even a gasket set there waiting to be used. All of that lot appears to be still in good condition, even after 40 years of storage.
So that's the good bit. The bad bit is that all of the rest of the engine parts are a complete jigsaw and a lot of it covered in 40 years' grime and surface rust. In most cases, the rust isn't deep enough to damage the parts, but obviously I don't want to rebuild the engine in that condition, so there is lots of deep cleaning required.
I have no idea whether all of the engine parts are there or not. It is just a massive jigsaw, but I have the various workshop manuals and parts lists etc to help me!
Also, I have never completely rebuilt an engine before! I've stripped top ends and barrels and I've dealt with clutches etc but never split a crankcase or rebuilt a gearbox. How hard can it be!
I thought I'd start with the big bits! The crank and gearbox/clutch assemblies were already out in separate units so that seemed as good a place to start as any.
I pulled the gearbox shafts and clutch apart, taking LOTS of photos and notes about which way it went together.
All of the parts were scrubbed in solvent, inspected and then the surface rust removed using a wire brush in the pillar drill. A list of new parts was started!
All of the gears looked fine with little wear and no obvious damage. The mainshaft bearing was seized, but I'd already decided that I was going to replace all of the bearings anyway after seeing the state of the crank roller bearing!
The clutch came apart fine and again looked in fairly good condition after a good clean. New friction plates went on the shopping list. I think I'll fit a new drive sprocket as well, mainly because it will be a bit of a pig to get to if I have to do it in 12 months time.
The crank looks to be in really good condition. I gingerly stripped back the masking tape covering the reground pin and it looked great once 40 year old goo from the tape had been cleaned off.
I pulled out the plugs in the sludge trap and there was very little sludge to clean out, so I'm guessing it was done a long time ago.
So moving on to the engine block, all I had done up to this point was lift the head off when I first got it (mainly to see if I could find a piston!)
With the barrel removed, I found that the piston had already been fitted with a new ring set - it's all ready to go. The cylinder is freshly honed, but has a very slight amount of surface rust, which will come off with some gentle application of fine emery paper and oil.
The cylinder head and barrel were filthy. I was going to send them to be vapour blasted, but needed to degrease them first. As I was doing that, I watched 40 years of grime come away from the surface and they are in surprisingly good condition. I'm going to spray the barrel black and just clean up the head. I also have a spare head which looks to be in better condition again but I won't make a decision on which to use until I've stripped them down.
Then it was time to split the case for the first time. I was really pleased with what I found:
I gave everything a really good clean and inspection and Scotchbrited the outer faces. Although good, they weren't without issues, mostly on the left hand primary case, where a number of the threaded holes for attaching the outer case had either stripped threads or, in the case of the two that sit in the drive chain tunnel, had been drilled out, presumably following damage. This is apparently a common thing, after people put a case screw in that's too long and it then gets damaged by the chain flapping against it.
So I am helicoiling three holes along the bottom of the case:
The two chaincase holes are slightly more complicated. I need to make up a couple of "bosses" to take 1/4" BSF case screws:
I've done helicoiling before and not too worried about that. But the bosses were something else - I ended up doing some very rudimentary and agricultural machining to form those. Basically, I got two 1/4" BSF nuts and also a matching bolt. I cut the head off the bolt and screwed one of the nuts onto it, then used the bolt as a shaft to mount the nut in my pillar drill. I moved the drill table up until I could use a file against the rotating nut to "machine" down the body of the nut to form a shoulder, but leaving about 2mm of hexagon as a flange. The pictures show it better than words really:
Then I drilled out the case to suit the diameter of the rounded part of the nut and epoxied it in to the case from behind.
Et voila - the threaded hole is restored! I was very pleased with myself at doing this - felt like I was channelling previous generations of Shearer engineers!
The final part of "cleaning/preparation" of the cases was to make sure that all of the internal oil passages are clear. I followed the excellent engine rebuild article by Jack Gray for this and it was good at the end of it to see fresh engine oil ooozing around the engine's veins and arteries!!
A nice (and also expensive) box of new engine bearings, seals and filter parts arrived so, once the helicoiling is done, we are ready to start rebuilding.
The most tedious part of the build so far has been to go through the boxes of grubby bits, cleaning and degreasing every last nut bolt and washer and then getting rid of any surface rust using the wire brush and pillar drill. But it's great that I now have a whole pile of clean stuff that may or may not have a part to play in the rebuild! What I have realised is that there are up to 3 engine's worth of certain parts so I have a few to play around with to get the best of the bunch.
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