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Tilting conrod

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When I took the piston off the Model 50 bottom end (alternator type) that I got for my racing project, I noticed that the conrod would tilt about 3 mm sideways, though no radial play could be felt, nor could I slide the conrod left and right. I couldn't feel radial or axial play on the crankshaft either. Is it normal for the conrod to tilt this much?

It's my first engine rebuild, so I doubt every step I make.

Cheers,

Tim

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Has all the oil been washed out with paraffin or similar?  It should be able to move sideways to allow the piston to align itself with the bore (as no doubt your book says).  The check on wear is that there is negligible up and down movement (or just perceptable...there does need to be somewhere for lubrication).  Oil (especially if old and sticky) can hide this.

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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.

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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.

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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...

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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!

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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.
 

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Hi Tim
I have a 1960 M50 (alternator type,) and as your last post suggested, any roller bearing does have a slight 'rock' mine does,
3mm at the little end is very small anyway.
I don't know where you are, but if in the UK contact our singles guru, M Pemberton, he has been very helpful to me in the past,and did a great job on the rebuild of my engine some time ago. also he is the man to speak to about tuning a M50, re his 'poor man's Manx'.
If you are thinking about racing the engine, I would have thought you would replace all suspect parts anyway, to prevent a major engine problem in the future.

Regards John O

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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.

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Hi Tim
I would suggest you don't even think about oversize rollers (even if they are available) a new one is available from the club shop, so check it out.
The Netherlands I assume is a great place to live, apart from the lack of hills! we have some friends that live near  Tilberg.
Regards John O (N Yorks)
 

 



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