Drive side crankcase, bearings and witness marks

[56G80S]

Another element of my Hampshire Jampot recovery marathon.

While I realised that the timing side bush was a problem, I was previously optimistic about drive side bearings.

Wrong! I've now thoroughly washed these out (I always use paraffin rather than petrol) and by the simple expedient of a cut off piece of broom handle wrapped in some cloth jammed into the bearing, find that they're kaput. That SAE 50 is really thick stuff

So that's more to do and money to spend.

But I also noticed that there's some very bright aluminium towards the bottom of the case, like the flywheel has rubbed against it? The crankshaft is at Alpha Bearings, so I can't look at it and didn't notice before I sent it. Everything's gone to pot.

Drive side crankcase small.jpg

I'll be doing some very careful dry run re-assembly and checking the alignment, end float and anything else I can read up on before the lot gets bolted back together.

Johnny B

[SPRIDDLER]

...... by the simple expedient of a cut off piece of broom handle wrapped in some cloth jammed into the bearing, find that they're kaput.

Jamming fingers into the inner race and spinning the outer is normally enough to reveal roughness in a knackered bearing.

But I also noticed that there's some very bright aluminium towards the bottom of the case, like the flywheel has rubbed against it?

I found the same markings on my 350 some years ago. Never did get to the bottom of why or how it had happened but assumed it had occurred before an earlier rebuild.
Purely idle lockdown conjecture John, but you said the t/s bush was done-for, so could it have been so worn that it allowed the c/shaft ass'y to tip enough for the f/wheel to tilt enough to contact the c/case? I doubt it though as I think it would have to tilt quite a lot and the big end, oil pump plunger splines and its drive scroll on the t/s axle would be hammered too.
Were the two 'washers' in place between the main bearings? Maybe there was too much end float on the f/wheel ass'y or the inner main migrated outwards.....
At least you're not missing any riding.

[56G80S]

Sprid

Yes, that's my normal approach but the carpal tunnel means that I have diminished sensation in the ends of my index finger in particular. Anyhow, I just wanted to be sure. I didn't want it to be the case and it's easy to fool yourself.

As you know, it's been mine since the mid 1970's so it's now very difficult to place blame on anyone else!

I think my year only has the one spacer but I've not taken the bearings out yet.

I reckon the timing side bush had at least 6 thou of play.

Thanks for the interest.

Johnny B

PS perhaps it's been there for a long time, the pattern crankpin snapped in the 1970's and "wedged" so I manged the remaining distance home.

[SPRIDDLER]

I think my year only has the one spacer but I've not taken the bearings out yet.

Yes, quite so. I missed that.

I reckon the timing side bush had at least 6 thou of play.

Nah, not anywhere near enough play to tilt the flywheel sufficient for it to contact the c/case.

PS perhaps it's been there for a long time, the pattern crankpin snapped in the 1970's and "wedged" so I manged the remaining distance home.

That sounds much more likely. I reckon mine was old scraping which had stayed shiny on account of the oily environment in the c/case.

Onward and upward!

[Mick D]

the pattern crankpin snapped in the 1970's and "wedged" so I manged the remaining distance home.

Hi

That's when the contact would have happened - don't over think things, replace the necessary parts and check clearances as you assemble, I'm sure it will be fine, (if a tad expensive).

Regards Mick