First job was to take off the chain and the clutch, I could have left the chain on but it needs a clean anyway. The thread on the crank is damaged, I did not want to damage it further by trying to turn the engine over by using a nut on it.
All this has to come off to see what is going on in there.
Ah, that might have some influence on the going up and down functionality. Bugger.
OH dear, that's not supposed to look like that.
Before I start this one I should correct an error I made in the last blog post about this bike - I called it a Triton, which is what I thought was common parlance for a bike with a Triumph engine and Norton gearbox. This faux pas created some merriment amongst classic bike aficionados, who were quick to correct me - a Triton is a Triumph engine in a Norton frame. I have tied a knot in a boot lace and shall administer an appropriate punishment to my nether regions later, but in the mean time, this.....
My workshop is full at the moment but curiosity got the better of me and I had to fiddle with the drag bike - it's just not in my nature to do things properly. It was still on the back of the van but all I wanted to do is see if the diesel had done anything in terms of freeing the engine off. I had already checked the gearbox, which feels absolutely superb, it's a 4 speed, all four gears and neutral engage quite easily, there is no nasty noise as far as the bearings are concerned.
Anyway, you know how these things go, I decided I needed a special tool to enable me to turn the engine over so I welded an old 1/2 inch drive socket to the sprocket and although I was expecting it to still be solid it took hardly any effort to make the locked up block turn. I was pretty much elated for about 3 seconds, at which point, near TDC it stopped pretty sharpish. Definitely sounded like something was hitting rather than something going tight. Sod it, sod my inquisitive nature and sod my bipolar disorder, the thing had to come apart. It's quite easy really, few bolts and nuts to get the valve covers off - one of which is not immediately obvious. The carbs were already off, the exhausts came off in minutes, then there are 8 bolts to remove to get the head off. Later bikes have 9 bolts, mine is an early 8 bolt one.
I half expected to see a valve stuck but no, they all looked fine, it looked pretty clean in there to. The next thing should have been to take Mrs shopping but I figured by shutting the van door she would never find me - cunning or what?
My plan worked and half an hour later the head was off and the problem was right there, staring me in the face - one of the bores had a mixture of diesel and water in it. I had put the diesel in but I'm pretty certain the water had been in there for a long, long time before I ever laid eyes on the beast. The bore is what can be best described as ruined, although I have to say below where the rings were sat it looks in really good nick. The left hand bore is perfect, the diesel washed off the very light coating of carbon that was present, apart from the top of the right bore it looks both fine and dandy. It's too far gone to use though so either a rebore or replacement is in order. The pistons are plus 30 thous, I measured the bore at 71.50mm, which is odd because the chart I found suggest that's a 20 thou overbore rather than 30. I have no idea what compression ratio they are or how to find out - more research is needed.
The bottom end feels really good, the crank spins beautifully, I can not detect any slop in the rods, I am pretty sure it was rebuilt not very many minutes running ago.
I have found two fantastic facebook groups full of experts on these engines - The National Sprint Association and the All Pre-Unit Triumph group. There are lots of very knowledgeable and helpful folk on there that have been brilliant this far, so I am really glad I found those two groups.
There had been some comments about how the heads on these bikes have a reputation for cracking so I was quite concerned about that. I decided quick clean up was in order, a few squirts of carb cleaner and a rub with a cloth were all that was needed to get rid of the light coating of carbon, I am glad to say I can see no sign of cracking and it all looks fairly recently breathed upon.
I will strip it so I can clean and inspect it properly, I will give the valves a grind while I am at it, the valve clearances will all need to be done once it's back together.
I want to measure the valves before I go much further as I am intrigued to see if they are standard or not.
So that's it for today, it's dark already, I needed the toilet so had to come out of the van and the Mrs spotted me and gave chase. I am now going to have to go to the supermarket, which is totally crap, they don't even sell bike parts in there.
This is much better. I like this.