Tilting conrod

The part of the text in your photo that said: "...may be that the engine still has more life left in it." did it for me. I'm taking it apart. It would be stupid the gamble when you go racing. So thanks for that shake up.

There's no oil in the engine, but I took off a quite worn ring spun piston (first, I thought someone bodged it with a hacksaw and some wire), so it must have been standing for decades. Dried residue might mask bigger problems.

I still find the amount of tilt with no feelable other play very strange though.

A 'little bit' and 'small amount' definitely don't feel like the amount of play that mine has. It feels like a straw in a glass that you can flick from side to side.

I'll split the engine and take a proper look.

A bit rough, but it feels more like old oil than pitted surfaces. But I still suspect the big end after removing the timing cover and discovering there's no oil feed jet (or spring)!

Are these made from bronze? I had a quick look and they're not readily available, so I might have to make one on the lathe.

As always, once you start...

Had to look up who that was... Not the easiest shop to find something, but we all like a challenge!

Yes, it seems he is the only one who actually has the parts. Cheers for that!

Regarding my initial question:

It might have been against better judgement, hoping someone would tell me: "They all do that!" 

I'll report back when I've asked an expert eye to check, for future reference when someone lands on this topic. For now, I'm back in the shed, making up a three toothed tool to remove the oil pump worm gear. New skills and insights learned every day.
 

You're right about replacing suspect parts. Although the challenge of this project is to prove it can be done on a budget, it would be foolish to ga racing (well, demo racing, so it's not quite as full on) with a dodgy engine.

I hadn't taken the old piston off yet, and as it slid on its gudgeon pin, the conrod tilt was masked by that. Well, for someone with my experience anyway. So, it wasn't suspect at first, but now it definitely is. Especially as the engine is missing the oil feed jet.

Regretfully, I live in the Netherlands, so sourcing parts and finding Norton specialists is a challenge on its own. I have contacted Mike Pemberton before and he's indeed very helpful. He is a busy man though and I suspect he gets bombarded with questions every day, so I'm a bit reluctant to contact him.

The timing gear is off now and the camshafts look in very good order, so there's hope that it's not all bad. I'll take the crankshaft out and let an engine expert look at it. In the best case scenario, he can use oversized rollers. worst case means finding a new big end bearing. Alpha Bearings has the N3, and there's also a Hepolite one, though I don't know who makes those. Fingers crossed though, that we can get away with oversized rollers.

It turns out that 3 mm tilt is way too much. When getting the crankshaft out, I held the small end with one hand, and hit it on top with the other. A clear 'clank' could be heard.

After pressing the crankshaft apart, it was very clear the big-end has had it. No pitting luckily, but a ridge could be felt in both the pin and the outer ring. The rollers are 6,35x6,35 mm (1/4x1/4) and I need a thou oversize (6,37 mm). These are available for Harley-Davidson, although they are 0,4 mm to long, so we'll have to find someone with a magnetic grinding table. If not, I have to fork out for a complete big-end, which will be about four times the cost of the rollers.

Anyway, there are options, so I'll get it sorted.

Regarding the oil jet; I made one from bronze. Mike Pemberton was so kind to measure one for me. He told me I could even make one from brass, but that material has me traumatised.

Just to give a conclusion to this post for future reference: the engineer helping me out, let me feel a freshly reconditioned crankshaft assembly and the conrod couldn't be tilted. I could just about feel a tiny bit of play if I really concentrated. Of course, there will be more play after some miles, but nothing like the amount of play like I had.

Just to give more info for future reference, regarding the oil jet:

– Outside diameter: 5/16″ (7,93 mm)
– Inside diameter: 7/32″ (5,49 mm)

– Length: that one got lost in translation. I noted down 11/32″ when I spoke to Mike, but that’s way too short when looking at pictures of those jets. I made it 14,87 mm, which is 75/128″, but I think 5/8″ might have been the original size, which is about 1 mm longer. Most important thing, is that it’s not so long, that the timing cover can’t shut.

I did have to search for a spring that was small enough to fit inside, but wide enough not to end up in the oilway. My advice: never throw even the smallest springs away and keep them in a box. They'll come in handy one day.