Hello again, fellas. It's been a while since I've updated anything, however I've been doing lots of reading and making a fair bit of progress (with the odd two steps backwards for one forwards).
I've changed the thread title to make this my build thread as I couldn't be arsed starting a new thread to cover previous ground again. So, since I last wrote anything, here's what I've been up to. Plenty grins, and plenty gremlins along the way...
At my last update, I had started to tear the engine down. It's grown arms and legs, as expected. The (447) con-rod small ends are badly worn, and their heads are black. The motor felt, to me at least, quite good, in that it was free revving, sounded sweet, and pulled well. But then I suppose that's testament to this lump. I know this engine is known for keeping going, at least fairly well, even when in a bit of a grim state. It was in dire need of a rebuild.
Progress with the engine:
top end disassembled and inspected. Pistons not looking good, absolutely caked in carbon and with severe scoring all round the skirts. The rings were worn beyond spec, too. The cam and rocker arms look in good condition fortunately. This engine had standard .952 pistons and it has not been subject to any rebore in its lifetime as far as I can tell. Valves are in spec in their guides, but will be lapped and the seats recut while everything is apart.
Knowing that the worn small ends require a crank rebuild made me want to cry a little bit, given I hadn't budgeted for much engine work in my youthful naivety / misplaced optimism. So, with the help of this forum, and my two manuals, I set about disassembling the bottom end and splitting the cases. At first very daunting (this is my first foray into motor work), however I've taken my time, and been as organised and as careful as I possibly could've been.
After prepping the bottom end for splitting, and definitely removing all 18 bolts / stud nuts(!), the cases were properly stuck together. After a lot of head scratching, heating, swearing, and losing skin from my knuckles, I managed to split them using the worlds smallest, simplest, puller. I used one M6 bolt and a couple of nuts wedged between the cases (wrapped in rags), very carefully opened the puller, and the cases prised apart locally just enough to allow me to work round their perimeter and get the job done. Satisfying.
I have had the top end vapour blasted. It looks great.
Headaches:
Someone has been at this motor previously, and the work done has been careless to put it kindly. I can't honestly remember all of the little things done badly, but most recently I discovered two of the dome nuts on the underside of the bottom case were missing their copper sealing washers (so that'll be where the leaking was coming from, then...), the head of one of the shoulder screws that retains the rear cam chain guide pivot arm is completely stripped and rounded out (haven't figured a solution for that one yet), and the case has been damaged around the countershaft sprocket oil seal and repaired with some sort of bodge. Predictably, that failed when I was removing the seal and so now I have to look into having that repaired. As I mentioned previously, the clutch push rod is badly bent, too. How that happened I have no idea.
Vapour blasted top end
Ready for painting the lettering
Clutch serviceable
Split...
Degreased with new strainer and sump plugs fitted
The green arrow indicates where the puller was placed to facilitate splitting the cases. Worked a treat.
Puller...
The offending rods
Phew
I've finished the front end now. Everything is rebuilt, powder coated, greased up, new needle roller headstock bearings etc. Looking good
Aside from the engine, I've got the frame completely bare, and I've started to de-tab it. I've also been playing around with CAD (cardboard aided design) to assist with making an electronics tray.
Far too deep currently, it'll be amended in due course.
So that's a bit of an update for anyone interested. In terms of next steps, I've got the swinging arm off being powder coated and I have new bronze bushings to install in that once it's back. The wheels are currently being rebuilt with stainless spokes, I'm looking forward to having them back and seeing them together with the new tyres and rejuvenated disc.
There's a local engine builder who is going to rebuild the crank for me with new rods and bearings, and I'm going to have the barrels rebored. It's all really rather expensive, isn't it? Who knew!
In terms of questions for the brains on here, can anyone advise why two of the screws that retain the camchain guide pivot arm are shouldered? Is there a a good reason not to replace those horrible screws with allen head set screws, for example?
Thanks for reading; all feedback, criticism, and piss taking welcome.
Cheers,
Mark