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Talked to Paul at Stafford about a jangly noise from the dart after a run and it was suggested I might check the crankshaft nut as that can be a problem. Checked it and found OK so went to Barbon Hill climb, as a spectator by the way, a round trip of about 130 miles. Very noisy on return and crank nut still tight as far as I could tell but on draining the oil found what appears to be parts of a bearing cage so dart sorned pending further investigation. Cage parts suggest a quite large bearing!

It's not completely unheard of for the drive side main bearing cage to fail.

I've just started a video series on an engine stripdown and inspection.

Paul, thank you in anticipation. I've an engine to strip and I enjoy and find your videos helpful.

Thanks Paul,
Watched the first part,most helpful and will be looking for the rest.
Cheers,Wilson

Hi seventy plus
I have some questions has the bike been stored or left fo a long time on the side stand rather than on paddock stand. Have you had problems with fuel overflow from rear carburettor.
Mark

Hi mbmm,
Bike I believe was off road for approx. ten years before I got it but I haven't had any rear carb flooding problems, does this point to anything.
Cheers, Wilson

Hi,

Bike I believe was off road for approx. ten years before I got it but I haven't had any rear carb flooding problems, does this point to anything.

The concern is that bikes stored for a long period of time without taking steps to prepare for storage have common issues.
Those relevant to the Dart are:

The first is that combustion by-product acids in the oil, which would remain below the bearings when on a main-stand
may reach the driving side main bearing if the bike is stored on the side stand with old engine oil inside.

The second concern is that breakdown of the fuel and/or loss of fuel from the carburetor can cause the float to stick down, or the valve to not seal properly.
The storage time here may be a matter of months.

Long term storage also affects batteries, tyres, plastic components, seat covers, oil seals, etc etc..

So for the Nikasil bored K4 engine the minimum expectation should be 100,000 km before an engine rebuild.

In this case it is far better to use the vehicle than store it.

Mark

It's taken some time to get to stripping the Dart engine and it is the drive side crank bearing cage broken up. Hopefully just the bearing needs changed but I will be looking at all the others while I'm in there. Everything else looks really good and bears out the recorded kilometres of around 42000.
The disassembly videos by the way Paul are really good, very helpful.
Is there any particular make or type of bearing I should be looking for to avoid a repeat of this?
-----Wilson.
PS I'd post a picture but I don't know how to!

Hello,

I used SKF from Simply bearings. I think the lot came to about £60. I think there are 7 roller bearings. I bought some others in that price for the starter which you will not have on the Dart as yours is an ugly thing at the front.

Thanks Mickeymoto for that, I do use simply bearings and find them very good. I just wondered if there was a known best bearing for this application. On the other subject yes I could agree ugly but I would have to add very reliably functional.
Cheers Wilson

All the bearings are C3 clearance.

Hi Wilson,

Is there any particular make or type of bearing I should be looking for to avoid a repeat of this?

Any high quality brand; SKF, Koyo, FAG for example, and as Paul says C3 clearance bearings are a must have.

As a point of clarification these bearings are described as "Deep groove ball bearings" not "roller bearings" which are something else.

For me the issue is not the bearing type:
I would store the bike with clean engine oil on paddock stands or similar.
This will also take the weight off the tyres

Question is it a 400 or 350 Dart?

Mark

Hi Mark, it is a 350 Dart and I did realise that they were deep groove ball bearings but thanks to both of you for telling me they were c3 clearance, I might have missed that. The bike by the way probably had stood for some 10 years or so before I got it and obviously I had no control over the way it was stored but the oil was fairly clean and the inside of it looks quite clean so far, crank cases still to split. I am considering replacing all the bearings while I'm there, the cost of them is very little compared the time and effort involved in doing it. Thanks again, Wilson

Crankcase now split, all stripped out, only damage seems to be the main bearing and everything is relatively clean without too much debris. Just need it all washed out, parts ordered and reassembled. Rear engine mount to repair so may paint frame parts before refitting engine.

Yes, ball bearings.

I was hoping that you would look at the originals to see C3 written on them!

The problem I had was domestic. I waited for t' gaffer to go to work before I put the cases in the oven to remove and then replace the bearings...